Disseminates successful models as part of a coordi nated effort to educate and reach out to the public (Hamburg, 1998;Mercy et al., 1993). The chapters in this report are keyed to each of these components of the public health approach. Chapter 2 presents research describing the magnitude by the University of Michigan's Institute for Social Research (Johnston et al., 1995) - Youth Risk Behavior Surveillance Study sponsored by the Centers for Disease Control and Prevention in collaboration with Federal, state, and local part ners (Brener et al., 1999)No single study, however well designed, is sufficient to establish causation or, in intervention research, effi cacy or effectiveness. Findings must be replicated before gaining widespread acceptance by the scientif ic community. The strength of the evidence amassed for any scientific fact or conclusion is referred to as the level of evidence.# Message from Donna E. Shalala

# Secretary o f Health and Human Services
The first, most enduring responsibility of any society is to ensure the health and well-being of its children. It is a responsibility to which multiple programs of the Department of Health and Human Services are dedicated and an arena in which we can claim many remarkable successes in recent years. From new initiatives in child health insur ance and Head Start, to innovative approaches to child care, to the investment in medical research that has amelio rated and even eliminated the threat of many once lethal childhood diseases, we have focused directly and con structively on the needs of millions of children. Through programs designed to enhance the strength and resiliency of families and family members across the life span and through our investments in diverse community resources, we are also helping to enhance the lives and enrich the opportunities of millions more of our children.
Although we can take rightful pride in our accomplishments on behalf of U.S. youths, we can and must do more. The world remains a threatening, often dangerous place for children and youths. And in our country today, the greatest threat to the lives of children and adolescents is not disease or starvation or abandonment, but the ter rible reality of violence.
We certainly do not know all of the factors that have contributed to creating what many citizens-young and old alike-view as our culture of violence. It is clear, however, that as widespread as the propensity for and tol erance of violence is throughout our society-and despite efforts that, since 1994, have achieved dramatic declines in official records of violence on the part of young people-every citizen must assume a measure of responsibili ty for helping to reduce and prevent youth violence. Information is a powerful tool, and this Surgeon General's report is an authoritative source of information.
In directing the Surgeon General to prepare a scholarly report that would summarize what research can tell us about the magnitude, causes, and prevention of youth violence, President Clinton sought a public health perspec tive on the problem to complement the extraordinary work and achievements in this area that continue to be real ized through the efforts of our criminal and juvenile justice systems. Over the past several months, the Department of Health and Human Services has worked with many hundreds of dedicated researchers, analysts, and policy makers whose interests and expertise lie outside the traditional domains of health and human services. What has become clear through our collaboration is that collectively we possess the tools and knowledge needed to throw safety lines to those young Americans who already have been swept up in the currents of violence and to strength en the protective barriers that exist in the form of family, peers, teachers, and the countless others whose lives are dedicated to the futures of our children. This Surgeon General's report seeks to focus on action steps that all Americans can take to help address the problem, and continue to build a legacy of health and safety for our young people and the Nation as a whole.

# n (

# Foreword
The opportunity for three Federal agencies, each with a distinct public health mission, to collaborate in developing the Surgeon General's report on youth violence has been an invigorating and rewarding intellectual challenge. We and our respective staffs were pleased to find that the importance that we collectively assign to the topic of youth violence transcended any impediments to a true, shared effort. Obstacles that one might have anticipated-for example, difficul ties in exchanging data and discussing concepts that emanate from many different scientific disciplines-proved to be surmountable. Indeed, many of the differences in perspective and scientific approach that distinguish the Centers for Disease Control and Prevention (CDC), the National Institutes of Health (NIH), and the Substance Abuse and Mental Health Services Administration (SAMHSA), when combined, afforded us a much fuller appreciation of the problem and much firmer grounds for optimism that the problem can be solved than is obvious from within the boundaries, or con fines, of a single organization.
The mission of CDC is to promote health and quality of life by preventing and controlling disease, injury, and dis ability. The NIH, of which the National Institute of Mental Health (NIMH) is one component, is responsible for gener ating new knowledge that will lead to better health for everyone. SAMHSA is charged with improving the quality and availability of prevention, treatment, and rehabilitation services in order to reduce illness, death, disability, and cost to society resulting from substance abuse and mental illnesses. Common to each of the agencies is an interest in prevent ing problems before they have a chance to impair the health of individuals, families, communities, or society in its entire ty. Toward this end, CDC, NIH/NIMH, and SAMHSA each support major long-term research projects involving nation ally representative samples of our Nation's youth. These studies, which are introduced and described in the report that follows, are designed both to monitor the health status of young Americans and to identify factors that can be shown to carry some likelihood of risk for jeopardizing health-information that lends itself to mounting effective interventions.
The designation of youth violence as a public health issue complements the more traditional status of the problem as a criminal justice concern. Here again, it has been satisfying for all of us in the public health sector to reach across professional and disciplinary boundaries to our colleagues in law, criminology, and justice and work to meld data that deepen our understanding of the patterns and nature of violence engaged in by young people throughout our country.
What has emerged with startling clarity from an exhaustive review of the scientific literature and from analyses of key new data sources is that we as a Nation have made laudable progress in gaining an understanding of the magnitude of the problem. We have made great strides in identifying and quantifying factors that, in particular settings or combi nations, increase the probability that violence will occur. And we have developed an array of interventions of welldocumented effectiveness in helping young people whose lives are already marked by a propensity for violence as well as in preventing others from viewing violence as a solution to needs, wants, or problems.
CDC, NIH/NIMH, and SAMHSA look forward to continuing collaborations, begun during the development of this report, that will extend further the abilities of policy makers, communities, families, and individuals to understand youth violence and how to prevent it.

# Preface from the Surgeon General U.S. Public Health Service
The immediate impetus for this Surgeon General's Report on Youth Violence was the Columbine High School tragedy that occurred in Colorado in April 1999, resulting in the deaths of 14 students, including 2 perpetrators, and a teacher. In the aftermath of that shocking event, both the Administration and Congress requested a report summa rizing what research has revealed to us about youth violence, its causes, and its prevention.
Our review of the scientific literature supports the main conclusion of this report: that as a Nation, we possess knowledge and have translated that knowledge into programs that are unequivocally effective in preventing much serious youth violence. Lest this conclusion be considered understated or muted, it is important to realize that only a few years ago, substantial numbers of leading experts involved in the study and treatment of youth violence had come to a strikingly different conclusion. Many were convinced then that nothing could be done to stem a tide of serious youth violence that had erupted in the early 1980s. During the decade extending from 1983 to 1993, arrests of youths for serious violent offenses surged by 70 percent; more alarmingly, the number of young people who committed a homicide nearly tripled over the course of that deadly decade. In many quarters, dire predictions about trends in youth violence yielded to resignation; elsewhere, fear and concern prompted well-meaning officials and policy makers to grasp at any proposed solutions, often with little, if any, systematic attention to questions of the efficacy or effective ness of those approaches.
Fortunately, the past two decades have also been distinguished by the sustained efforts of researchers, legislators, and citizens from all walks of life to understand and address the problem of youth violence. One seminal contribu tion to these efforts was an initiative taken by one of my predecessors, Surgeon General C. Everett Koop, to address violence as a public health issue; that is, to apply the science of public health to the treatment and prevention of vio lence. As evident throughout this report, that endorsement was key to encouraging multiple Federal, state, local, and private entities to invest wisely and consistently in research on many facets of youth violence and to translate the knowledge gained into an exciting variety of intervention programs.
Although much remains to be learned, we can be heartened by our accomplishments to date. For one, our care ful analyses, together with those conducted by components of the justice system, have demonstrated the pervasive ness of youth violence in our society; no community is immune. In light of that evidence, it has been most encour aging to me to see that the citizens with whom I have interacted in hundreds of communities around the Nation want us to find answers that will help all of our youth. There is a powerful consensus that youth violence is, indeed, our Nation's problem, and not merely a problem of the cities, or of the isolated rural regions, or any single segment of our society.
Equally encouraging have been our findings that intervention strategies exist today that can be tailored to the needs of youths at every stage of development, from young childhood to late adolescence. There is no justification for pessimism about reaching young people who already may be involved in serious violence. Another critical bit of information from our analyses of the research literature is that all intervention programs are not equally suited to all children and youths. A strategy that may be effective for one age may be ineffective for older or younger children. Certain hastily adopted and implemented strategies may be ineffective-and even deleterious-for all children and youth.
Understanding that effectiveness varies underscored for us the importance of bridging the gap between science and practice. Only through rigorous research and thorough, repeated evaluations of programs as they operate in the real world will we be assured that we are using our resources wisely.
In presenting this Surgeon General's report, I wish to acknowledge our indebtedness to the many scientists who have persisted in their work in this difficult, often murky area and whose results we have scrutinized and drawn on. We are also immensely grateful to the countless parents, police officers, teachers, juvenile advocates, health and human service workers, and people in every walk of life who recognize the inestimable value of our Nation's youth and the importance of peace, security, and comity in their lives.      For millions of youths and their families, a period of life that should have been distinguished by good health and great promise was instead marred by injuries, disability, and death . This epidemic of violence not only left lasting scars on victims, perpetrators, and their families and friends, it also wounded communities and, in ways not yet fully understood, the country as a whole.
Since 1993, the peak year of the epidemic, there have been some encouraging signs that youth vio lence is declining. Three important indicators of violent behavior-arrest records, victimization data, and hospital emergency room records-have shown significant downward trends nationally. These offi cial records reveal only a small part of the picture, however.
A fourth key indicator of violence-confidential reports by youths themselves-reveals that the pro portion of young people who acknowledge having committed serious, potentially lethal acts of physical violence has remained level since the peak of the epi demic. In 1999, for instance, there were 104,000 arrests of persons under age 18 for robbery, forcible rape, aggravated assault, or homicide (Snyder, 2000); of those arrests, 1,400 were for homicides perpetrated by adolescents (Snyder, 2000) and, occasionally, even younger children ). Yet in any given year in the late 1990s, at least 10 times as many youths reported that they had engaged in some form of violent behavior that could have seriously injured or killed another person.
The high prevalence of violent behavior reported by adolescents underscores the importance of this report at this time.
Americans cannot afford to become complacent. Even though youth violence is less lethal today than it was in 1993, the percentage of adolescents involved in violent behavior remains alarmingly high. The epi demic of lethal violence that swept the United States was fueled in large part by easy access to weapons, notably firearms-and youths' self-reports of violence indicate that the potential for a resurgence of lethal violence exists. Yet viewing homicide as a barometer of all youth violence can be quite misleading. Similarly, judging the success of violence prevention efforts solely on the basis of reductions in homicides can be unwise.
This report, the first Surgeon General's report on youth violence in the United States, summarizes an extensive body of research and seeks to clarify seem ingly contradictory trends, such as the discrepancies noted above between official records of youth vio lence and young people's self-reports of violent behaviors. It describes research identifying and clari fying the factors that increase the risk, or statistical probability, that a young person will become violent, as well as studies that have begun to identify devel opmental pathways that may lead a young person into a violent lifestyle. The report also explores the less well developed research area of factors that seem to protect youths from viewing violence as an accept able-or inevitable-way of approaching or respond ing to life events. Finally, the report reviews research on the effectiveness of specific strategies and pro grams designed to reduce and prevent youth violence.
As these topics suggest, the key to preventing a great deal of violence is understanding where and when it occurs, determining what causes it, and scientifically documenting which of many strategies for prevention and intervention are truly effective. This state-of-thescience report summarizes progress toward those goals.
The most important conclusion-of the report is that the United States is well past the "nothing works" era with respect to reducing and preventing youth vio lence. Less than 10 years ago, many observers pro jected an inexorably rising tide of violence; the recent, marked reductions in arrests of young perpetrators and in victimization reports appear to belie those dire pre dictions. We possess the knowledge and tools needed to reduce or even prevent much of the most serious youth violence. Scientists from many disciplines, working in a variety of settings with public and pri vate agencies, are generating needed information and putting it to use in designing, testing, and evaluating intervention programs.
The most urgent need now is a national resolve to confront the problem of youth violence systematically, using research-based approaches, and to correct dam aging myths and stereotypes that interfere with the task at hand. This report is designed to help meet that need.
The report makes it clear that after years of effort and massive expenditures of public and private resources, the search for solutions to the problem of youth violence remains an enormous challenge Sechrest et al., 1979). Some tra ditional as well as seemingly innovative approaches to reducing and preventing youth violence have failed to deliver on their promise, and successful approaches are often eclipsed by random violent events such as the recent school shootings that have occurred in com munities throughout the country.
Youth violence is a high-visibility, high-priority concern in every sector of U.S. society. We have come to understand that young people in every community are involved in violence, whether the community is a small town or central city, a neatly groomed suburb, or an isolated rural region. Although male adolescents, particularly those from minority groups, are dispro portionately arrested for violent crimes, self-reports indicate that differences between minority and major ity populations and between male and female adoles cents may not be as large as arrest records indicate or conventional wisdom holds. Race/ethnicity, consid ered in isolation from other life circumstances, sheds little light on a given child's or adolescent's propensi-"^T~r engaging in violence.
This chapter describes the scope and focus of the report and explains how the public health approach advances efforts to understand and. prevent youth violence. Common myths about youth violence are presented and debunked. Uncorrected, these myths lead to misguided public policies, inefficient use of public and private resources, and loss of traction in efforts to address the problem. Documentation for the facts that counter these myths appears in later chapters. This chapter also lays out the scientific basis of the report-that is, the standards of evidence that research studies had to meet in order to be included in the report and the sources of data cited throughout. Final sections of this chapter preview subsequent chapters and list the report's major conclusions.

# Sc o p e , Fo c u s , a n d O v e r a r c h in g T h e m e s
The mission of the Surgeon General is to protect and improve the public health of the Nation, and this report was developed within the responsibilities and spirit of that mission. The designation of youth vio lence as a public health concern is a recent develop ment. As discussed below in greater detail, public health offers an approach to youth violence that focuses on prevention rather than consequences. It provides a framework for research and intervention that draws on the insights and strategies of diverse disciplines. Tapping into a rich but often fragmented knowledge base about risk factors, preventive inter ventions, and public education, the public health per spective calls for examining and reconciling what are frequently contradictory conclusions about youth violence.
Although the public health approach opens up a broad array of considerations, the focus of this initial report is the perpetration by juveniles of interpersonal physical assault that carries a significant risk of injury or death. As restrictive as it may at first appear, this focus draws on a wealth of research into individual, family, school, peer group, and community factors that are associated with serious violence in the second decade of life. This report defines serious violence as aggravated assault, robbery, rape, and homicide; here after, it refers simply to "violence" or "violent crime," thus avoiding repetitious use of the terms "serious vio lence" or "serious violent crime."
The report views violence from a developmental perspective. It examines the interactions of youths' personal characteristics and the social contexts in which they live-as well as the timing of those inter actions-to understand why some young people become involved in violence and some do not. This perspective considers a range of risks over the life course, from prenatal factors to factors influencing whether patterns of violent behavior in adolescence will persist into adulthood. The developmental per spective has enabled scientists to identify two general onset trajectories of violence: one in which violent behaviors emerge before puberty, and one in which they appear after puberty. Of the two, the early-onset trajectory provides stronger evidence of a link between early childhood experiences and persistent, even lifelong involvement in violent behavior. The developmental perspective is important because it enables us to time interventions for the particular point or stage of life when they will have the greatest positive effect.
The young people on whom this report focuses are principally children and adolescents from about age 10 through high school. Research reviewed in Chapter 4 shows that although risk factors for vio lence vary by stage of development, most youth vio lence emerges during the second decade of life. Appropriate interventions before and-as is increas ingly well documented-during this period have a good chance of redirecting violent young people toward healthy and constructive adult lives. The win dow of opportunity for effective interventions opens early and rarely, if ever, closes.

# S e c o n d a r y A r e a s o f C o n c e r n
Many legitimate concerns and issues that are indis putably associated with violence by young people are not addressed in depth in this first report. Behavioral patterns marked by aggressiveness, antisocial behav ior, verbal abuse, and externalizing (the acting out of feelings) are peripheral to the main focus of the report. These behaviors may include violent physical interactions, such as hitting, slapping, and fist-fight ing, that can have significant consequences but gen erally present little likelihood of serious injury or death. Therefore, such behaviors will be discussed only to the extent that they can be considered risk fac tors for violence.
Research has shown that victims and offenders share many personal characteristics and that victim ization and perpetration of violent behavior are often entwined. Nonetheless, this report does not focus on victims of violence perpetrated by young offenders. Rather, it blends offender-based research with tradi tional public health concepts of prevention and inter vention in an effort to bridge the gap between crimi nology and the social and developmental sciences, on the one hand, and traditional public health approaches to youth violence, on the other.
The report does not address violence against inti mate partners, except when such violence is committed by a young person. The plight of victims, many of whom are children and adolescents, is of the utmost importance, but a key element in helping victims of violence is understanding the perpetrators of violence. Particular categories of crime, such as dating violence and hate crimes (motivated by racist or homophobic attitudes, for example), are important manifestations of violence, including violence committed by youths, and they demand research and targeted interventions. The limited amount of research conducted in this area has focused on victims, so there is little scientific evidence about what distinguishes perpetrators of these specific types of crimes (see reviews by Bergman, 1992;Comstock, 1991;and D'Augelli & Dark, 1984).
Self-directed violence-that is, self-inflicted injury and suicide-is not covered either. In collabo ration with other Federal health agencies, the Office of the Surgeon General developed a National Strategy for the Prevention of Suicide (U.S. Public Health Service, 1999). In directing national attention to suicide as a major, yet largely preventable public health problem, the Surgeon General is bringing together health professional organizations, educa tors, health care executives, and managed care clini-cal directors to discuss gaps in scientific knowledge that impede efforts to decrease the incidence of suicide among Americans of all ages. The vast majority of youth suicides occur in the context of mental disorders (Brent et al., 1988;Shaffer et al., 1996), a topic that was reviewed in depth in the Surgeon General's report on mental health (U.S. DHHS, 1999).
Finally, the report does not propose public policy to reduce or prevent youth violence. The purpose of this report, like others from U.S. Surgeons General, is to review and describe existing knowledge in order to provide a basis for action at all levels of society. The last chapter identifies potential courses of action, including specific areas in which research is needed, but suggesting whether and how such action will lend itself to policy development is beyond the purview of this report.

# Y o u t h V io l e n c e : T h e P u b l ic H e a l t h A p p r o a c h
In October 1985, Surgeon General C. Everett Koop convened an unprecedented Workshop on Violence and Public Health (U.S. DHHS, 1986). The partici pants agreed strongly that it was time public health perspectives and expertise were brought to bear on questions of crime and violence. Throughout much of the last century, these questions had been domi nated by the social sciences and the criminal justice system. For the most part, health care efforts were restricted to the rehabilitation of convicted offenders (Sechrest et al., 1979;U.S. DHHS, 1986). Dissatisfaction with both the timing and the out comes of the "rehabilitation ideal" spurred the search - for a more effective role for health care in addressing violence.
With its emphasis on prevention of disease or injury, the public health approach to violence offers an appealing alternative to an exclusive focus on rehabilitation. Primary prevention identifies behav ioral, environmental, and biological risk factors associated with violence and takes steps to educate individuals and communities and protect them from these risks. Central to education and protection is the iciple that health promotion is best learned, per-ERLC formed, and maintained when it is ingrained in indi viduals' and communities' daily routines and percep tions of what constitutes good health practices. Public health practitioners and advocates have taken the lead in encouraging alliances and networks among academic disciplines, professions, organiza tions, and communities to make health concerns per manent public priorities and part of personal practices. In that tradition, participants at the 1985 Surgeon General's conference emphasized the importance of convincing the public that violence should be treated as a public health problem. As Marvin Wolfgang, a distin guished leader in the field of criminology, told confer ees, "Our nation must feel as comfortable in controlling its violent behavioral urges and practices as it does in controlling bacterial, viral, and physical manifestations of morbidity and death" (U.S. DHHS, 1986).
Just as the application of public health principles and strategies has reduced the number of traffic fatal ities and deaths attributed to tobacco use (CDC, 1999), the public health approach can help reduce the number of injuries and deaths caused by violence. Broader than the medical model, which is concerned with the diagnosis, treatment, and mechanisms of spe cific illnesses in individual patients, public health offers a practical, goal-oriented, and communitybased approach to promoting and maintaining health. To identify problems and develop solutions for entire population groups, the public health approach:
- Defines the problem, using surveillance processes designed to gather data that establish the nature of the problem and the trends in its incidence and prevalence;
- Identifies potential causes through epidemiological analyses that identify risk and protective factors associated with the problem;
- Designs, develops, and evaluates the effectiveness and generalizability of interventions; and

# Introduction
-f the problem of violent behavior by young people. Chapter 3 explores how violence develops and emerges over time. Chapter 4 summarizes research on risk and protective factors for youth violence; Appendix 4-B elaborates on the effects of exposure to media violence (including violence in interactive media) as a risk factor for aggressive and violent behavior. Chapter 5 focuses on the design, evaluation, and refinement of numerous programs and strategies that seek to reduce or prevent youth violence; Appendix 5-B provides details on specific programs discussed in the chapter. Chapter 6 suggests future courses of action, including the necessary next steps in research. A glossary of technical and disciplinespecific terms follows.

# M y t h s A b o u t Y o u t h V io l e n c e
An important reason for making research findings widely available is to challenge false notions and mis conceptions about youth violence. Myths such as those listed below are intrinsically dangerous.
Assumptions that a problem does not exist or failure to recognize the true nature of a problem can obscure the need for informed policy or for interventions. An example is the conventional wisdom in many circles that the epidemic of youth violence so evident in the early 1990s is over. Alternatively, myths may trigger public fears and lead to inappropriate or misguided policies that result in inefficient use of scarce public resources. An example is the current policy of waiving or transferring young offenders into adult criminal courts and prisons.

# Myth: The epidemic o f violent behavior that marked the early 1990s is over, and young people-as well as the rest o f U.S. society-are much safer today.
Fact: Although such key indicators of violence as arrest and victimization data clearly show significant reductions in violence since the peak of the epidemic in 1993, an equally important indicator warns against concluding that the problem is solved. Self-reports by youths reveal that involvement in some violent behav iors remains at 1993 levels (see Chapter 2).
Myth: Most future offenders can be identified in early childhood.
Fact: Exhibiting uncontrolled behavior or being diagnosed with conduct disorder as a young child does not predetermine violence in adolescence. A majority of young people who become violent during their ado lescent years were not highly aggressive or "out of control" in early childhood, and the majority of chil dren with mental and behavioral disorders do not become violent in adolescence (see Chapter 3).
Myth: Child abuse and neglect inevitably lead to violent behavior later in life.
Fact: Physical abuse and neglect are relatively weak predictors of violence, and sexual abuse does not predict violence. Most children who are abused or neglected will not become violent offenders during adolescence (see Chapter 4).
Myth: African American and Hispanic youths are more likely to become involved in violence than other racial or ethnic groups.
Fact: Data from confidential interviews with youths indicate that race and ethnicity have little bear ing on the overall proportion of racial and ethnic groups that engage in nonfatal violent behavior. However, there are racial and ethnic differences in homicide rates. There are also differences in the tim ing and continuity of violence over the life course, which account in part for the overrepresentation of these groups in U.S. jails and prisons (see Chapter 2).

# Myth: A new violent breed o f young superpreda tors threatens the United States.
Fact: There is no evidence that young people involved in violence during the peak years of the early 1990s were more frequent or more vicious offenders than youths in earlier years. The increased lethality . resulted from gun use, which has since decreased dra matically. There is no scientific evidence to document the claim of increased seriousness or callousness (see Chapter 3).

# Myth: Getting tough with juvenile offenders by trying them in adult criminal courts reduces the like lihood that they will commit more crimes.
Fact: Youths transferred to adult criminal court have significantly higher rates of reoffending and a greater likelihood of committing subsequent felonies than youths who remain in the juvenile justice system.
They are also more likely to be victimized, physically and sexually (see Chapter 5).

# Myth: Nothing works with respect to treating or preventing violent behavior.
Fact: A number of prevention and intervention programs that meet very high scientific standards of effectiveness have been identified (see Chapter 5).
Myth: In the 1990s, school violence affected mostly white students or students who attended sub urban or rural schools.
Fact: African American and Hispanic males attending large inner-city schools that serve very poor neighborhoods faced-and still face-the greatest risk of becoming victims or perpetrators of a violent act at school. This is true despite recent shootings in suburban, middle-class, predominantly white schools (see Chapter 2).

# Myth: Weapons-related injuries in schools have increased dramatically in the last 5 years.
Fact: Weapons-related injuries have not changed significantly in the past 20 years. Compared to neigh borhoods and homes, schools are relatively safe places for young people (see Chapter 2).

# Myth: Most violent youths will end up being arrested fo r a violent crime.
Fact: Most youths involved in violent behavior will never be arrested for a violent crime (see Chapter 2).

# So u r c e s o f D a ta a n d St a n d a r d s o f Ev id e n c e

# Data Sources
Several comprehensive scholarly reviews of various facets of youth violence were published in the 1990s. Professional organizations, Federal agencies, the National Academy of Sciences, and university-based researchers have invested immense energy in reviewing research on the occurrence and patterns of youth violence, its causes and consequences, interven tion strategies, and implications for society.
Key contributions to this rich information base include:
- NIMH Taking Stock o f Risk Factors fo r Child/Youth Externalizing Behavior Problems (Hann & Borek,
- Serious and Violent Juvenile Offenders    - The American Psychological Association's report Violence and Youth (APA, 1993) and Reason to Hope (Eron et al., 1994) - Preventing Crime: What Works, What Doesn't, What' s Promising. A Report to the United States Congress (Sherman et al., 1997) - The OJJDP national report Juvenile Offenders and Victims  - The American Sociological Association's Social Causes o f Violence: Crafting a Science Agenda (Levine & Rosich, 1996) This report draws extensively-but not exclusive ly-on concepts, general information, and data con tained in these documents. The authors gratefully acknowledge the contributors to and publishers of these earlier studies. Whenever the report draws heav ily on one of these master sources, that fact is noted. Specific references to these documents are provided where appropriate.
Contributors to and editors of this report have also consulted peer-reviewed journals, books, and govern ment reports and statistical compilations. Some infor mation not considered in prior reviews is contained in this report. When appropriate, the editors have drawn on dissertations and forthcoming work that they judged to be of high quality.
During the development of this report, special data analyses were obtained from established surveys of U.S. adolescents. The key data sources for these analyses are the following:   - The National Center for Juvenile Justice's up-todate information on juvenile arrests for violent crimes (Snyder, 2000) - The National Crime Victimization Survey (Rand et al., 1998)

# Standards of Scientific Evidence for Multidisciplinary Research
The public health approach relies on a multidiscipli nary, multijurisdictional knowledge base. Thus, in preparing this report, it was necessary to draw conclu sions from research in psychology (social, develop mental, clinical, and experimental), sociology, crimi nology, neuroscience, public health, epidemiology, communications, and education. Integrating findings and conclusions across disciplinary lines is never easy.
The questions under study generally determine what approach scientists will take to designing and conduct ing research, and the approach often determines how investigators report their findings and conclusions. Even when scientific approaches are similar, investiga tors in different disciplines frequently employ different terminology to describe similar concepts.
In striving to apply scientific standards consis tently across the many fields of research reviewed, this report has emphasized two criteria: appropriately rigorous methods of inquiry and sufficient data to sup port major conclusions. The need for rigor is obvious: The tools or strategies employed in research-like the conclusions reached-are only as good as the preci sion with which research questions are framed. But the quality of a given study depends on other factors as well, including:
- General data collection design. Data may be obtained through four major types of study design:
experimental, longitudinal, cross-sectional, and case study. This report relies primarily on experimental and longitudinal designs, with some use of cross sectional studies. (These three methods are described below.)
- Sampling, or the selection of persons to be studied. Individuals in a study may be recruited or identi fied through probability or nonprobability sam pling, or they may be assigned to experimental or control groups by a random process, a precision or group-matching process, or some other means. This report refers to probability samples as repre sentative samples.
- Validity and reliability of measures or instruments used in the research.
- Appropriateness and level of control incorporated into the analysis of findings. Level of control refers to efforts to take into account other factors that might be influencing data or responses from subjects.
- Appropriateness and significance of generalizations.
As noted earlier, four of the chapters in this report-those concerned with magnitude, demograph ics, risk and protective factors, and intervention research and evaluation-mirror components of the public health approach to youth violence. Each of these areas involves research from different disci plines and scientific approaches; therefore, the types of research designs and forms of analysis presented differ somewhat from chapter to chapter.
Experimental research is the preferred method for assessing cause and effect as well as for determining how effectively an intervention works. Many of the violence prevention programs reviewed in Chapter 5 meet the standard of rigorous experimental (or wellexecuted quasi-experimental) designs. In an experi mental study, researchers randomly assign an inter vention to one group of study participants, the experi mental group, and provide standard care or no inter vention to another group, the control group. A study with a randomly assigned control group enables researchers to conclude that observed changes in the experimental group would not have happened without the intervention and did not occur by chance. The dif-ference in outcome between the experimental and control groups, which in this case may be the reduc tion or elimination of violent behaviors, can then be attributed to the intervention.
Ideally, researchers assign study participants to the experimental intervention or the control group at random. Randomization eliminates bias in the assign ment process and provides a way of determining the likelihood that the effects observed occurred by chance. In this report, most weight is given to true experimental studies. In some cases, true experiments may be too difficult or expensive to conduct, or they may pose unacceptable ethical problems. In such cases, carefully designed and executed quasi-experi mental studies are accepted as meeting the standard.
Evidence from an experimental study is consid ered stronger when, in addition to analyzing the main effects of an intervention, researchers analyze the mediating effects. This analysis permits researchers to determine whether a change in the targeted risk or protective factor accounts for the observed change in violence-that is, did the intervention work because it changed the degree of risk? Without this information, researchers cannot explain the success of a program.
Chapters 4 and 5 make use of meta-analyses. Meta-analysis describes a statistical method for eval uating the conclusions of numerous studies to deter mine the average size and consistency of the effect of a particular treatment or intervention strategy com mon to all of the studies. The technique makes the results of different studies comparable so that an over all effect can be identified. A meta-analysis deter mines whether there is consistent evidence that a treat ment has a statistically significant effect, and it esti mates the average size of that effect.
Epidemiological research, reviewed in Chapters 2 and 3, focuses primarily on general population studies that use probability samples and cross-sectional or lon gitudinal designs (Kleinbaum et al., 1982;Lilienfeld & Lilienfeld, 1980;Rothman & Greenland, 1998). Probability samples let researchers generalize from their study to the entire population sampled. Cross-sec tional studies involve a single contact with participants for data collection at a given point in time. Multiple O cross-sectional studies involve several waves of data collection over time (annually, for example) but typi cally with different participants at each contact and therefore with no way to link a given person's respons es at one time with those at a later time. Prospective longitudinal and panel designs involve multiple con tacts with the same study participants over time.
Responses at one data collection point can be linked to responses at a later point. Longitudinal studies are used for research on individual development or growth.
Longitudinal designs are necessary to estimate the predictive effect of a given risk or protective factor on later violent behavior. Although cross-sectional designs are sometimes used, they cannot provide estimates of individual-level predictive effects. They can establish simultaneous relationships between risk factors and vio lence, but conclusions drawn from cross-sectional stud ies are not as strong as those drawn from longitudinal studies. In cross-sectional studies, cause and effect are unclear and reciprocal effects may inflate the estimates.
Experimental studies are sometimes used to esti mate the effects of risk and protective factors, but this practice is rare because of ethical and cost considera tions. For example, it would be unthinkable to intro duce drug use to a group of adolescents to see whether drugs are a risk factor for violence. However, it would be ethical to conduct a predictive study that selects persons who are not violent and follows them over time. Those who began to use illicit substances would be compared with those who did not, to determine whether drug users are more likely to become involved in violent behaviors at some later date. If they were, then the results would indicate that drug use predicts violence or that drug use increases the probability of future violence.

# Introduction
This report does not rely on any single study for conclusions. Only findings that have been replicated in several studies, consistently and with no contrary results, are reported as part of the contemporary knowl edge base. When the report cites unreplicated studies that are of high quality, that have not been refuted by other evidence, and that point in a clear direction, the findings are described as tentative or suggestive. These findings may point to future research needs and direc tions, but the report takes a conservative approach to drawing conclusions from them.

# O v e r v ie w o f t h e R e p o r t 's C h a p t e r s
The Surgeon General's report on youth violence reviews a vast, multidisciplinary, and often controver sial research literature. Chapters 2 through 5 address, respectively, the extent and magnitude of youth vio lence; the developmental characteristics of, or paths to, youth violence; personal and environmental factors that may either place a child or adolescent at risk of violent behavior or protect a young person from suc cumbing to those risk factors; and violence interven tion and prevention programs. The final chapter in the report identifies areas of opportunity for future efforts to combat and prevent youth violence.
This section provides a brief overview of each chapter, while the following section presents a sum mary of key conclusions drawn from each.
Chapter 2 examines the magnitude of and trends in youth violence over the last two decades. It describes two different, but complementary ways of measuring violence-official reports and self-reports. Official arrest data offer an obvious means of deter mining the extent of youth violence. Indeed, a surge in arrests for violent crimes marked what is now recog nized as an epidemic of youth violence from 1983 to 1993. Arrests were driven largely by the rapid prolif eration of firearms use by adolescents engaging in violent acts and the likelihood that violent confronta tions would-as they did-produce serious or lethal injuries. Today, with fewer young people carrying weapons, including guns, to school and elsewhere than in the early 1990s, violent encounters are less likely to result in homicide and serious injury and therefore are less likely to draw the attention of police. By 1999, arrest rates for homicide, rape, and robbery had all dropped below 1983 rates. In contrast, arrest rates for aggravated assault remained higher than they were in 1983, having declined only 24 percent from the peak rates in 1994.
Another way of measuring violence is on the basis of confidential reporting by youths themselves. Confidential surveys find that 10 to 15 percent of high school seniors report having committed an act of seri ous violence in recent years. These acts typically do not come to the attention of police; in part because they are less likely to involve firearms than in previ ous years. Over the past two decades, self-reported violence by high school seniors increased nearly 50 percent, a trend similar to that found in arrests for vio lent crimes. But this proportion has not declined in the years since 1993-it remains at peak levels. Chapter 2 considers how and to what extent arrest data and self report data vary, including variations by sex and race or ethnicity. In the aggregate, the best available evi dence from multiple sources indicates that youth vio lence is an ongoing national problem, albeit one that is largely hidden from public view.
Chapter 3 examines routes that may lead a young person into violence. Viewed from a developmental perspective, violence stems from a complex interac tion of individuals with their environment at particu lar times in their lives. Longitudinal research has enabled investigators to describe the emergence of violence in terms of two, and possibly more, lifecourse trajectories. Chapter 3 discusses the earlyonset and late-onset emergence of violence, which occur before and after puberty, respectively. These trajectories offer insights into the likely course, severity, and duration of violence over the life course and have practical implications for the timing of intervention programs and strategies. The chapter reviews research on the co-occurrence of serious vio lence and other problems, including drug use and mental disorders. Finally, it underscores the impor tance-and the paucity-of research on factors asso ciated with the cessation of youth violence or its con tinuation into adulthood.
Extensive research in recent decades has sought to identify various personal characteristics and environ mental conditions that either place children and ado lescents at risk of violent behavior or that seem to pro tect them from the effects of risk. Risk and protective factors, which are the focus of Chapter 4, can be found in every area of life. They exert different effects at dif ferent stages of development, they tend to appear in clusters, and they appear to gain strength in numbers. As the chapter notes, risk probabilities apply to groups, not to individuals. Although risk factors are not necessarily causes, a central aim of the public health approach to youth violence is to identify these predictors and determine when in the life course they typically come into play. Such information enables researchers to design preventive programs that can be put in place at just the right time to be most effective.
The chapter examines risk from the perspectives of both childhood and adolescence and, within each of these developmental periods, considers risk factors occurring in the individual, family, school, peer group, and community domains. Childhood risk factors for violence in adolescence include involvement in serious (but not necessarily violent) criminal acts and sub stance use before puberty, being male, aggressiveness, low family socioeconomic status/poverty, and antiso cial parents-all either individual or family risk fac tors. The influence of family is largely supplanted in adolescence by peer influences, thus risk factors with the largest predictive effects in adolescence include weak social ties, ties to antisocial or delinquent peers, and belonging to a gang. Having committed serious (but not necessarily violent) criminal offenses is also an important risk factor in adolescence.
Identifying and understanding how protective fac tors influence behavior is potentially as important to preventing and stopping violence as identifying and understanding risk factors. Several protective factors have been proposed, but to date only two have been found to buffer the risk of violence-an intolerant atti tude toward deviance and commitment to school. Protective factors warrant, and are beginning to receive, more research attention.
Despite past contentions that "nothing works" to prevent youth violence, the evidence presented in Chapter 5 demonstrates that prevention efforts can be effective against both early-and late-onset violence in the general youth population, high-risk youths, and even youths who are already violent or seriously delin quent. The chapter highlights 27 specific programs that, based on existing data, help prevent youth vio lence. The most effective of these programs combine components known to prevent violence by themselves, particularly social skills training for youths and inter ventions that include parents or entire families.
Chapter 5 also highlights important limitations in the current research on youth violence prevention.
Little is known about the scientific effectiveness of hundreds of programs now being used in U.S. schools and communities. This situation is disconcerting, given that many well-intentioned youth violence pre vention programs have been found ineffective or harmful to youths. Even less is known about how to implement effective programs on a national scale without compromising their results.
The information presented in Chapter 5 shows that youth violence prevention not only works, it can also be cost-effective. In a number of cases, the long term financial benefits of prevention are substantially greater than the costs of the programs themselves. These promising findings indicate that prevention plays an important role in providing a safe environ ment for youths.
Finally, Chapter 6 presents several options for future action. First, the scientific base must continue to be expanded. Effective interventions exist, but only continued research can document those programs that meet a standard of effectiveness and those that do not-and should therefore be discarded. The chapter identifies the following courses of action:
- Disseminate model programs with incentives that will ensure fidelity to original program design when taken to scale
- Provide training and certification programs for intervention personnel
- Improve public awareness of effective interventions
- Convene youths and families, researchers, and pri vate and public organizations for a periodic youth violence summit
- Improve Federal, state, and local strategies for reporting crime information and violent deaths

# C h a p t e r C o n c l u s io n s
Chapter 2
1. The decade between 1983 and 1993 was marked by an epidemic of increasingly lethal violence that was associated with a large rise in the use of firearms and involved primarily African American males. There was a modest rise in the proportion of young persons involved in other forms of seri ous violence.
2. Since 1994, a decline in homicide arrests has reflected primarily the decline in use of firearms.
There is some evidence that the smaller decline in nonfatal serious violence is also attributable to declining firearm use.
3. By 1999, arrest rates for violent crimes-with the exception of aggravated assault-had fallen below 1983 levels. Arrest rates for aggravated assault remain almost 70 percent higher than they were in 1983, and this is the offense most fre quently captured in self-reports of violence.
4. Despite the present decline in gun use and in lethal violence, the self-reported proportion of young people involved in nonfatal violence has not declined from the peak years of the epidemic, nor has the proportion of students injured with a weapon at school declined.
5. The proportion of schools in which gangs are ' present continued to increase after 1994 and has only recently (1999) declined. However, evidence
shows that the number of youths involved with gangs has not declined and remains near the peak levels of 1996. r 6. Although arrest statistics cannot readily track firearm use in specific serious crimes other than homicide, firearm use in violent crimes declined among persons of all ages between 1993 and 1998.
7. The steep rise and fall in arrest rates for homicide over the past two decades have been matched by similar, but less dramatic changes in some of the other indicators of violence, including arrest rates for all violent crimes and incident rates from vic tims' self-reports. This pattern is not matched by arrests for selected offenses, such as aggravated assault, or incident rates and prevalence rates from offenders' self-reports.
8. Young men-particularly those from minority groups-are disproportionately arrested for vio lent crimes. But self-reports indicate that differ ences between minority and majority populations and between young men and young women may not be as large as arrest records indicate or con ventional wisdom holds. Race/ethnicity, consid ered in isolation from other life circumstances, sheds little light on a given child's or adolescent's propensity for engaging in violence.
9. Schools nationwide are relatively safe. Compared to homes and neighborhoods, schools have fewer homicides and nonfatal injuries. Youths at greatest risk of being killed in school-associated violence are those from a racial or ethnic minority, senior high schools, and urban school districts.

# Chapter 3
1. There are two general onset trajectories for youth violence-an early one, in which violence begins before puberty, and a late one, in which violence begins in adolescence. Youths who become vio lent before about age 13 generally commit more crimes, and more serious crimes, for a longer time. These young people exhibit a pattern of escalating violence through childhood, and they sometimes continue their violence into adulthood.
2. Most youth violence begins in adolescence and ends with the transition into adulthood.
3. Most highly aggressive children or children with behavioral disorders do not become serious vio lent offenders.
4. Surveys consistently find that about 30 to 40 per cent of male youths and 15 to 30 percent of female youths report having committed a serious violent offense by age 17.
5. Serious violence is part of a lifestyle that includes drugs, guns, precocious sex, and other risky behaviors. Youths involved in serious violence often commit many other types of crimes and exhibit other problem behaviors, presenting a serious challenge to intervention efforts. Successful interventions must confront not only the violent behavior of these young people, but also their lifestyles, which are teeming with risk.
6. The differences in patterns of serious violence by age of onset and the relatively constant rates of individual offending have important implications for prevention and intervention programs. Early childhood programs that target at-risk children and families are critical for preventing the onset of a chronic violent career, but programs must also be developed to combat late-onset violence.
7. The importance of late-on set violence prevention is not widely recognized or well understood. Substantial numbers of serious violent offenders emerge without warning signs in their childhood. A comprehensive community prevention strategy must address both onset patterns and ferret out their causes and risk factors.

# Chapter 4
1. Risk and protective factors exist in every area of life-individual, family, school, peer group, and community. Individual characteristics interact in complex ways with people and conditions in the environment to produce violent behavior.
O 2. Risk and protective factors vary in predictive power depending on when in the course of devel opment they occur. As children move from infan cy to early adulthood, some risk factors will become more important and others less important. Substance use, for example, is a much stronger risk factor at age 9 than it is at age 14.
3. The strongest risk factors during childhood are involvement in serious, but not necessarily violent criminal behavior, substance use, being male, physical aggression, low family socioeconomic status or poverty and antisocial parents-all indi vidual or family characteristics-or conditions. .
During adolescence, the influence of family is largely supplanted by peer influences. The strongest risk factors are weak ties to convention al peers, ties to antisocial or delinquent peers, belonging to a gang, and involvement in other criminal acts.
5. Risk factors do not operate in isolation-the more risk factors a child or young person is exposed to, the greater the likelihood that he or she will become violent. Risk factors can be buffered by protective factors, however. An adolescent with an intolerant attitude toward deviance, for example, is unlikely to seek or be sought out by delinquent peers, a strong risk factor for violence at that age.
6. Given the strong evidence that risk factors predict the likelihood of future violence, they are useful for identifying vulnerable populations that may benefit from intervention efforts. Risk markers such as race or ethnicity are frequently confused with risk factors; risk markers have no causal rela tion to violence.
7. No single risk factor or combination of factors can predict violence with unerring accuracy. Most young people exposed to a single risk factor will not become involved in violent behavior; similar ly, many young people exposed to multiple risks will not become violent. By the same token, pro , tective factors cannot guarantee that a child exposed to risk will not become violent.

# Introduction
Chapter 5
1. A number of youth violence intervention and pre vention programs have demonstrated that they are effective; assertions that "nothing works" are false.
2. Most highly effective programs combine compo nents that address both individual risks and envi ronmental conditions, particularly building indi vidual skills and competencies, parent effective ness training, improving the social climate of the school, and changes in type and level of involve ment in peer groups.
3. Rigorous evaluation of programs is critical. While hundreds of prevention programs are being used in schools and communities throughout the coun try, little is known about the effects of most of them.
4. At the time this report was prepared, nearly half of the most thoroughly evaluated strategies for pre venting violence had been shown to be ineffec tive-and a few were known to harm participants.
In schools, interventions that target change in the social context appear to be more effective, on average, than those that attempt to change indi vidual attitudes, skills, and risk behaviors.
6. Involvement with delinquent peers and gang membership are two of the most powerful predic tors of violence, yet few effective interventions have been developed to address these problems.
7. Program effectiveness depends as much on the quality of implementation as the type of interven tion. Many programs are ineffective not because their strategy is misguided, but because the quali ty of implementation is poor.

# P r e p a r a t io n o f t h e R e p o r t
To address the troubling presence of violence in the lives of U.S. youths, the Administration and Congress urged the Surgeon General to develop a report on youth violence, with particular focus on the scope of the prob lem, its causes, and how to prevent it. Surgeon General Dr. David Satcher requested three agencies, all compo nents of the Department of Health and Human Services, to share lead responsibility for preparing the report. The agencies are the Centers for Disease Control and Prevention (CDC), the National Institutes of Health (NIH), and the Substance Abuse and Mental Health Services Administration (SAMHSA). Under Dr. Satcher's guidance, these agencies established a Planning Board comprising individuals with expertise in diverse disciplines and professions involved in the study, treatment, and prevention of youth violence. The Planning Board also enlisted individuals representing various Federal departments, including particularly the Department of Justice (juve nile crime aspects of youth violence), the Department of Education (school safety issues), and the Department of Labor (the association between youth violence and youth employment, and out-of-school youth). Invaluable' assistance was obtained as well from individual citizens who have founded and oper ate nonprofit organizations designed to meet the needs of troubled and violent youths. Most important, young people themselves accepted invitations to become involved in the effort. All of these persons helped to plan the report and participated in its prepublication reviews.

# Introduction
Rand, M. R., Lynch, J. R, & Cantor, D. (1997). Criminal victimization, 1973

# H
eadlines proclaim that the epidemic of youth violence that began in the early 1980s is over, but the reality behind this seemingly good news is far more complex and unsettling. Public health stud ies show that youth violence is an ongoing, startling ly pervasive problem. This chapter describes the magnitude of and trends in violent crime by young people, focusing on homicide, robbery, aggravated assault, and forcible rape (see Box 2-1 for defini tions). A later chapter (Chapter 4) seeks to explain why young people become involved in violence in the first place.

# M e a s u r in g Y o u t h V io l e n c e
Surveillance is the backbone of the public health approach to youth violence or any other public health problem. It reveals the magnitude of a problem, tracks the magnitude over time, and uses the information gained from such monitoring to help shape actions to prevent or combat the problem.
Two approaches to measuring the magnitude of youth violence are commonly used. The first relies on official crime statistics compiled by law enforcement agencies, typically arrest reports. These statistics can not answer questions about how many young people commit violent crimes or how many violent crimes were committed, but they can answer questions about the number of crimes reported to the police, the vol ume and types of arrests, and how the volume changes over time.
The second approach surveys young people and asks them in confidence about violent acts they have committed or have been victims of during a given period of time. Such reports can be obtained from the same group of people over a long period of time (a lon gitudinal survey) or from different groups of people at

# Criminal Homicide-Murder and Non Negligent Manslaughter
The willful (non-negligent) killing of one human being by another.

# Robbery
The taking or attempting to take anything of value from the care, custody, or control of a person or persons by force or threat of force or violence and/or putting the victim in fear.

# Aggravated Assault
An unlawful attack by one person upon another wherein the offender uses a weapon or displays it in a threatening manner, or the victim suffers obvious severe or aggravated bodily injury involving appar ent broken bones, loss of teeth, possible internal injury, severe laceration, or loss of consciousness.

# Forcible Rape
The carnal knowledge of a person, forcibly and/or against that person's will, or not forcibly or against the person's will where the victim is inca pable of giving consent because of his/her tempo rary or permanent mental or physical incapacity (or because of his/her youth). the same point in time (a cross-sectional survey). A prominent example of a repeated cross-sectional sur vey cited in this chapter is Monitoring the Future, a survey of high school seniors, that has been conducted annually since 1975. Reports from young people them selves offer the best way to measure violent behavior that never reaches the attention of the justice system. In fact, evidence in this chapter makes it unmistakably clear that most crimes by young people do not reach the attention of the justice system.
Self-reports are well suited to answering such questions as: What proportion of youths are violent? What types of violent acts do they commit? Has the volume of violence changed over time? Are there dif ferences by sex and race/ethnicity? When during development does violence arise, and what forms does it take? How do children's patterns of violence evolve over time, and how long do they last? These questions relate to the magnitude of violent behavior and to its developmental pathways, and they are addressed in this chapter and the next.
Both arrest reports and self-reports are reason ably valid and reliable ways of measuring the partic ular aspects of violence they were designed to meas ure (for general reviews see Blumstein et al., 1986;Hindelang et al., 1981;Huizinga & Elliott, 1986). Arrests appear to be more objective, but they are not a good general measure of violent behavior, for sev eral reasons. First, the majority of aggravated assaults, robberies, and rapes are never reported to the police; arrests are made in fewer than half of reported crimes Maguire and Pastore, 1999;; and most youths involved in violent crimes are never arrested for a violent crime . Thus, arrests seriously underestimate the volume of violent crime and fail to distinguish accurately between those who are and are not involved in violence. Second, arrest records do not accurately reflect the distribution of reported vio lent crimes; that is, the offenses for which youths are arrested are not representative of the crimes reported to police . Nonetheless, arrest records are the best measure of the justice system's response to observed or reported crime.
Self-reports were designed specifically to over come the limitations of violence measures based on official records of criminal behavior. They provide a more direct measure of criminal behavior, but they too have their limitations. Youths may fail to report their violent behavior accurately, either deliberately or because of memory problems, and they may exaggerate their involvement, reporting rather trivial events in response to questions about serious forms of violence. Research reveals that exaggeration (overreporting) is a greater problem than underreporting for reports that cover the previous year , but sophisticated self-report measures can minimize these potential sources of error Huizinga & Elliott, 1986). The advantages of self reports are that they capture not only unreported offens es but also details not found in arrest records. In' addi tion, this measure of violent offending is not subject to any of the biases that might be involved in arrest processes.' The general conclusion from studies evalu ating the validity and reliability of self-reports is that they compare favorably with other standard, accepted social science indicators (Hindelang et al., 1981).
Both types of measures contribute to our under standing of violence. The key to using them is to understand their relative strengths and limitations, determine where they reinforce each other and where they diverge or conflict, and then interpret the differ ences in findings, if possible (Brener et al., 1995;Hindelang et al., 1981;Huizinga & Elliott, 1986;.

# T h e V io l e n c e Ep id e m ic
Arrest rates of young people for homicide and other violent crimes skyrocketed from 1983 to 1993. In response to the dramatic increase in the number of Questions have been raised about potential racial/ethnic biases in both types o f measures. There is evidence that arrests o f whites, compared to those o f African Americans, are underrepresented in local arrest records and archives (Ceerken, 1994). Some studies find racial/ethnic bias in arrests and other justice system processing, w h ile others do not (for reviews, see Austin & Allen, 2000;Hawkins et al., 1998;Sampson & Lauritsen, 1997). Comparisons o f an individual's arrest and self-reported offenses reveal a greater discrepancy for African Americans than whites, w ith African American males self-reporting fewer o f the offenses found in their official records (Hindelang et al., 1981;Huizinga & Elliott, 1986). If one accepts the accuracy o f arrest records, this finding w ould indicate an underreporting on the part o f African American males, but there are reasons to question this assumption (see Elliott, 1982;Huizinga & Elliott, 1986). The question o f racial/ethnic bias in both asures remains controversial.
murders committed by young people, Congress and many state legislatures passed new gun control laws, established boot camps, and began waiving children as young as 10 out of the juvenile justice system and into adult criminal courts. Then, starting in the mid-1990s, overall arrest rates began to decline, returning by 1999 to rates only slightly higher than those in 1983. Several important indicators were used to track youth violence during these years, but their findings did not always agree. Arrest rates, as noted above, pro vide strong evidence of both a violence epidemic between 1983 and 1993/1994 and a subsequent decline to 1999. Several other indicators of violence furnish similar, but not as robust evidence of a violence epi demic that later subsided. However, the decline in arrest rates is not uniform for all types of violent crime. Moreover, another key indicator-the volume of vio lent behavior, which is based on self-reports-does not show a decline in youth violence after 1993. As explained later, that indicator remained high and essen tially level from 1993 to 1998. This chapter answers the questions raised by these disparate findingsnamely, whether the epidemic of violence is really over and why leading indicators of youth violence do not agree.
. A rise and subsequent decline in the use of firearms and other weapons by young people provides one potential explanation for the different trends in arrest records and self-reports. The violence epidemic was accompanied by an increase in weapons carrying and use. During this era, instant access to weapons, especially firearms, often turned an angry encounter into a seriously violent or lethal one, which, in turn, drew attention from the police in the form of an arrest. As weapons carrying declined, so too did arrest rates, perhaps because the violence was less injurious or lethal. But the amount of underlying violent behavior (on the basis of self-reports) did not change much-if anything, it appears to have increased in recent years. That undercurrent of violent behavior could reignite into a new epidemic if weapons carrying rises again. From a public health perspective, a resurgence of weapons carrying-and hence the potential for anoth er epidemic of violence-poses a grave threat.

# A r r e s t s f o r V io l e n t C r im e s
The Federal Bureau of Investigation (FBI) monitors arrests made by law enforcement agencies across the United States through the Uniform Crime Reporting (UCR) program. Since the 1930s, this program has compiled annual arrest information submitted volun tarily by thousands of city, county, and state police agencies. This information currently comes from police jurisdictions that represent only 68 percent of the population, so FBI figures represent projections of these data to the entire U.S. population .
The UCR tabulates the number, rate, and certain features of arrests made by law enforcement agencies. Because some people are arrested more than once a year, the UCR cannot provide an accurate count of the number of people arrested or the proportion of the total population arrested (the prevalence). Nor can the UCR provide an accurate count of the number of crimes committed. A single arrest may account for a series of crimes, or a single crime may involve the arrest of more than one person. Young people tend to commit crimes in groups, so the number of youths arrested inflates the number of crimes committed . As noted earlier, arrest rates are also prone to certain types of error. Unless indicated otherwise, the figures on arrests were assembled by the FBI.

# Arrest Rates and Trends
As shown in Figure 2-1, overall arrest rates for vio lent crimes by youths between the ages of 10 and 17 rose sharply from 1983 to 1993/1994. Rates then declined until 1999, the most recent year for which figures are available.
Figure 2-2, page 21, shows arrest rates for each of the four violent crimes considered in this report. In 1999, arrests of young people for all crimes totaled 2.4 million (Snyder, unpublished), with 104,000 arrests for violent crimes. Arrests for aggravated assault (69,600) and robbery (28,000) were the most frequent, with arrests for forcible rape (5,000) and murder (1,400) trailing significantly behind. In 1998, youths crimes, a share that has decreased slightly (16 percent) in recent years (Snyder, unpublished). Although the 1999 arrest rate for violent crimes was the lowest in this decade, it is still 15 percent higher than the 1983 rate (Snyder, unpublished). As seen in Figure 2-2, the 1999 rates for homicide, robbery, and rape are below the 1983 rates; however, arrests for aggravated assault are still nearly 70 percent higher than 1983 rates.
The sheer magnitude of the increase in arrest rates between 1983 and 1993/1994 is striking. Overall, arrest rates of youths for violent offenses grew by about 70 percent. The increase in homicides commit ted by young people was particularly alarming. Both the rate of homicide arrests and the actual number of young people who were arrested for a homicide near ly tripled . This increase was consistent for adolescents at each age between 14 and 17 .
The decade-long upsurge in homicides was tied to an increased use of firearms in the commission of crimes (Cherry et al., 1998;. Likewise, the downward trend in homicide arrests from 1993 to 1999 can be traced largely to a decline in firearm usage. The critical role of firearms in homicide and other violent crimes is supported by arrest, victim ization, hospitalization, and self-report data.
Analysis of arrest data (Figure 2-3, page 22) shows an unequivocal upsurge in firearm usage by young people who committed homicide. In 1983, youths were equally likely to use firearms and other weapons, such as a knife or club, to kill someone. By 1994, 82 percent of homicides by young people were committed with firearms . Virtually all of the increase in firearm-related homi cides involved African American youths . The precipitous drop in homicides between 1994 and 1998 coincided with a decline in firearm usage, again mostly by African American youths . of firearm use. A large increase in the number of young people killed by firearms between 1987 and 1993 was followed by a decrease. More than 2,000 youths were homicide victims in 1993, the peak year . Most victims were male, and a disproportionately high percentage were African American males .
The use of firearms in violent crimes other than homicide cannot readily be tracked in youth arrest sta tistics, but for Americans of all ages, firearm use in violent crimes increased from 1985 to 1992 and then declined from 1993 to 1998. Firearm use during rob beries increased 33 percent between 1985 and 1992; the decline in firearm use from 1993 to 1998 was nearly 20 percent for aggravated assaults but only 6 Firearm use can also be tracked indirectly, through victims treated in hospital emergency depart ments. Since 1992, injuries related to firearms have been monitored through an emergency department surveillance system.- 3 Although there are no data from this source to corroborate the growing pattern of firearm injuries before 1992, there are data to corrob orate the decline since then. Figure 2-A presents a spe cial analysis of emergency department surveillance data on youths age 10 to 19. It shows that the rate of firearms-related injuries among young people treated in hospital emergency departments dropped by almost 50. percent from 1993 to 1998. Data on male youths alone reveal a similarly dramatic drop.
Youths are victim s in about 27 percent o f homicides comm itted by other youths .
3 The National Electronic Injury Surveillance System (NEISS); NEISS is operated by the U.S. Consumer Product Safety Commission.
. A O *On 1 or more of the 30 days preceding the survey. 95% confidence intervals for carried weapon =  1.3-2.3; for carried weapon at school =  0 .9-1.5; and for carried gun =  0 .8 -1 .3 .
In the early 1990s, high school students began to report that they were increasingly less likely to carry guns anywhere and specifically less likely to carry them to school. Figure 2-5 illustrates these trends, as well as trends in general weapons carrying, based on data from the Youth Risk Behavior Survey (YRBS).4 Each trend shows a significant linear decrease, although the decline in weapons carrying in general leveled off in 1999 CDC, 2000a;Kann et al., 2000).
Thus, there has been an upsurge and then a decline in the use of firearms and weapons over the past two decades. The easy availability of guns and the resulting rise in lethal violence was caused at least in part by the emerging crack cocaine markets in the mid-1980s and the recruitment of youths into these markets, where carrying guns became routine (Blumstein & Wallman, 2000). It also resulted from changes in the types of guns manufactured, with cheaper, larger caliber guns flooding the gun markets (Wintemute, 2000).
The reasons for the decline are complex and not well understood, but they do involve changes in the car rying and use of guns in violent encounters (Blumstein & Wallman, 2000). The explanations most often given are a decline in youth involvement in the crack market and in gang involvement in crack distribution, police crackdowns on gun carrying and illegal gun purchases, longer sentences for violent crimes involving a gun, a strong economy, and expanded crime and violence pre vention programs. After reviewing these and other potential explanations for the drop in violence, Blumstein and Wallman (2000) concluded that no sin gle factor was responsible; rather, the decrease in vio lence resulted from the combination of many factors.

# Comparing Arrests to Other Trends
As noted above, the steep rise and fall in arrest rates over the past two decades has been matched to some extent by changes in leading indicators of violence. Figure 2-6 tracks the trends in four indicators: arrest rates for homicide only, arrest rates for all serious vio lent crimes, incident rates from victims' self-reports, and incident rates from offenders' self-reports. The incident rate is a measure of the volume of violence. It refers to the number of self-reported vio lent acts within a given-sized population-in this case, the number of violent acts per 1,000 young peo ple. In contrast, the prevalence rate indicates what proportion of that population is involved in one or more violent behaviors. Figure 2-6 compares arrest rates with self-reported incident rates (rather than with prevalence rates) because both measure the volume of violent events. Even though arrest and incident rates measure different events and have different absolute magnitudes, the degree of change in these rates over time can be compared. 0

# Arrests Versus Self-Reported Incidents
The sharpest increases in Figure 2-6 are for the two arrest indicators. Homicide arrest rates were roughly 170 percent higher in 1993 than in 1983, and arrest rates for all serious violent crimes were 70 percent higher. The incident rates of serious violent crimes reported by victims and the rates of serious assault and robbery reported by offenders increased to a lesser extent, by about 50 percent.
By 1999, arrest rates for homicide, robbery, and rape had dropped below their 1983 levels; by 1997, victim-reported incident rates had dropped back to roughly their 1983 levels. Arrests for aggravated assaults remained high, however-at almost 70 per cent above their 1983 level. Since the peak year of arrests for aggravated assault (1994), arrests for this violent crime have declined only 24 percent.
Self-reported violent offending showed no decline at all. After rising by about 50 percent, the incident rate of self-reported serious assaults and robbery remained essentially level through 1998.. The leveling off of  This self-reported incident rate appears to be much higher (e.g., almost 400 assaults w ith injury and robberies w ith a weapon were reported per 1,000 high school seniors in 1998) than the arrest rate for aggravated assault and robbery (about 350 arrests per 100,000 youth, see Figure 2-2), but the tw o are not strictly comparable: high school seniors (17-and 18-year-olds) have much higher arrest rates as a group than do 10-to 17-year-olds.
The MTF prevalence estimates for both violent behavior and drug use have been confirm ed by other studies in which there is overlap in years and ages. For example, see  and Menard and Elliott (1993). About 16,000 high school seniors at 130 schools participate, although only about 3,000 o f the students are asked questions about their v io lent behavior. Since the beginning o f the survey in 1975, the participation rate among schools has ranged from 60 to 80 percent, and the stu dent response rate has ranged from 77 to 86 percent (Kaufman et al.,199?' determining the extent of youth violence. They fur nish a window into violent behavior that never reach es the police. For example, the National Crime Victimization Survey reveals that the majority (58 percent) of serious violent crimes committed by youths are not reported to the police . A large fraction of the crimes that are reported never result in an arrest. Estimates indi cate that only 6 to 14 percent of chronic violent offenders are ever arrested for a serious violent crime (Dunford & Elliott, 1984;Elliott, 2000a;Huizinga et al., 1996;.
The MTF gathers data about five acts of violence and from them compiles a violence index (see Figure 2-8 for the specific offenses included). This violence index is not the same as the UCR violent crime index, which aggregates the four types of arrests covered in this chapter. According to the MTF's vio lence index, about 3 out of 10 high school seniors reported having committed a violent act in the past year, an annual prevalence rate of about 30 percent. The M TF's violence index has been relatively stable for almost 20 years, in sharp contrast to the. dramat ic increase in arrests.
' Although the prevalence rate of self-reported vio lent behavior is relatively constant, it is still strikingly high, partly because high school seniors age 17 and 18 are at the peak ages of violent offending and partly because the violence index includes some less serious violent behaviors as well as some very serious ones.
Because this report focuses on violent behavior carrying the potential for serious injury or death, Figure 2-8 also includes the prevalence rates of assault with injury and robbery with a weapon, the two most serious acts in the MTF violence index. An assault with injury could lead to an arrest for aggravated assault; likewise, a robbery with a weapon could lead to an arrest for armed robbery. Therefore, assault with injury and rob bery with a weapon may be used as proxy measures for aggravated assault and armed robbery, respectively.
Over the past two decades, the MTF's prevalence rates for assault with injury ranged from 10 to 15 per cent ( 1.3 to 1.8). A small but significant increase took place between 1979 and 1998. About half of this increase occurred between 1983 and 1993, but rates remained fairly constant after 1993 (the increase from 1993 to 1998 shown in Figure 2-8 is not statistically significant). The prevalence of robbery with a weapon ranged from 2 to 5 percent ( 0.7 to 1.1) between 1983 and 1993 and remained constant thereafter. Thus, unlike arrest data, MTF data show no evidence of a downward trend in self-reported assaults or robberies after 1993.
Prevalence rates of this magnitude-10 to 15 per cent of high school seniors8-for the most serious types of violence are confirmed by other self-report surveys described in Chapter 3. For example, an aver age prevalence rate of 9 percent ( 2.0) was reported for 17-year-olds between 1976 and 1982 in the National Youth Survey, whose measure of violence includes aggravated assault, robbery, gang fights, and rape. This rate is similar to the MTF's, but the National Youth Survey measure includes more serious violent offenses. Two general city surveys-the Denver Youth Survey and the Rochester Youth Development Survey, which use the same measure of violence as the National Youth Survey-report some what higher prevalence rates among 17-year-olds: 12 percent ( 1.6) and 14 percent ( 2.0), respectively.9

# International Prevalence
Are U.S. youths unique in reporting a high prevalence of violent behavior? How do they compare to their European counterparts? The answers can be found by comparing the MTF findings with the International Self-Report Delinquency Study (Junger-Tas et al., 1994), a study of delinquent behavior conducted in several European countries.
Like the MTF, this study relies on self-reported behavior. Of the countries included, only England/Wales, the Netherlands, Spain, and Italy used a probability sample that provided national estimates of violence comparable to the violence index used in the MTF survey. Self-reported serious violence

# Year
Sources: Rates for violence index: Johnston, 2000; rates for assault with injury and robbery with weapon: Maguire and Pastore, 1999.
Entries above are 3-year running averages of the prevalence of each of the specified acts. The violence index is defined as the percent committing any of the specified following five acts, with no missing data allowed: hit an instructor or supervisor; gotten into serious fight in school or at work; taken part in a fight where a group of your friends were against another group; hurt somebody badly enough to need bandages or a doctor (assault with injury); used a knife or gun or some other thing (like a club) to get something from a person (robbery with a weapon). 95% confidence intervals for the violence index are all less than  2.5%; for assault, less than  2%; for robbery, less than  1.1%.
among young people age 16 to 17 in these countries in 1992 or 1993 ranged from 16 to 26 percent (Table 2-1). These prevalence rates are lower than the U.S. rate of about 30 percent for the MTF's violence index. Thus, while the questions in the international study may be somewhat different, the findings show that while a higher proportion of U.S. youths commit vio lent acts, youth violence is not unique to the United States.
A major difference between the United States and several other industrial countries is the ease of access to firearms. From 1990 to 1995, the United States had the highest rate of firearm-related deaths among youths in the industrialized world (CDC, 1997). The rate for children below age 15 was five times higher than that of 25 other countries combined.
In summary, youth violence, although interna tional in scope, is greater in the United States, more likely to involve firearms, and more lethal in its con sequences. According to self-reports, both the preva lence and incidence (volume) of assault and robbery increased among U.S. high school seniors between 1983 and 1993. This finding is consistent with an epi demic of violence among U.S. youths, although self reports point to a more modest upsurge than arrest trends do. However, both self-reports and arrest rates for aggravated assault point to an ongoing problem of youth violence after the apparent end of the violence epidemic. Thus, the rise and fall in arrest rates for most violent offenses is set against more enduring rates of violent behavior.

# D if f e r e n c e s b y S ex a n d Ra c e /Et h n ic i t y
Self-reported violence and arrest rates for violent offenses can also be compared by sex and by race/ethnicity. Ratios based on these two sources of data show similar findings with respect to sex but remarkably different findings with respect to race/ethnicity-dif ferences that have yet to be fully explained.  , 1983 to 1993 and 1993 to 1998. In gen eral, there was little change in those periods, with one exception.
In 1983 and 1993, the ratios of male to female youths committing violent acts were 7.4 to 1 and 7.0 to 1, respectively. This means that for every violent act committed by female youths in these years, at least seven violent acts were committed by male youths. By 1998, this ratio had closed to 3.5 to 1, indicating that O l. -M liE S T C O P Y A V A ILA B LE females are closing the gap. The difference in preva lence rates changed little over the same period, but at a ratio of 2 to 1, it was much smaller to begin with. Taken together, the trends show that the proportions of males and females involved in violence (the. preva lence rate) have not changed but that the relative num ber of violent acts by males and females (the incident rate) has changed, with females committing more vio lent acts in 1998 than in earlier years.
Differences by race are also presented in Table 2-2. The only available national comparisons for seri ous violence are for white and African American youths (see Chapter 3 for local longitudinal studies that include rates for Hispanic youths). Overall, inci dent rates are lower for white than African American youths over these years; the gaps are largest in 1993 and 1998, when approximately 1.5 violent acts were 49  ---------------"  committed by African Americans for every 1 violent act b y whites. The racial gap appeared to increase somewhat during the violence epidemic and has remained higher through 1998. There are essentially no differences by race in the prevalence rates for seri ous self-reported violent behavior.

# Differences in Arrest Rates
Arrest rates differed widely by sex and by race/ethnicity between 1983 and 1998 (Table 2-3). Overall, the dif ference was greater by sex than by race/ethnicity and was most evident in regard to homicide arrests: In 1998, 11 times as many males were arrested as females. A sim ilar male-female gap was evident for robbery, but the gap for aggravated assault was considerably smaller. Trends in the male-female gap vary, depending on the crime for which youths are arrested. From 1983 to 1993, the male-female disparity in homicide arrests doubled: In other words, the violence epidemic was driven by arrests of males. During the same period, the male-female gap in arrests for both robbery and aggravated assault shrank. More recently, from 1993 to 1998, the male-female disparity in all three types of arrests has held constant or declined further.
Differences in arrest rates by sex are similar in magnitude to differences in self-reported violent inci dents. Combining aggravated assault and robbery arrest data yields male:female ratios of 6.8 to 1, 5.7 to 1, and 4.3 to 1 for 1983, 1993, and 1998, respective ly.10 The ratios for self-reported incidents were 7.4 to 1, 7.0 to 1, and 3.5 to 1 (Table 2-2). Thus, both self report and arrest rates attest to a difference by sex in the volume of violence but also to a narrowing of that gap between 1983 and 1998-except for homicide arrests. Possible reasons for the male-female gap are discussed in Chapter 4.
Self-reports and arrest rates provide different pic tures of violent offending by race. Self-reports, as noted above, reveal small differences between African American and white youths. Arrest records, on the other hand, reveal large differences, even though these gaps narrowed between 1993 and 1998 (Table 2-3). The narrowing of the gap was particularly noteworthy for homicide arrests: Whereas about nine African American youths were arrested for every white youth in 1993, only about five were arrested for each white youth in 1998. Even at 5 to 1, the ratio of African American to white youths arrested for homicide remains greater than that of Native American or Asian youths to white youths.
Ratios cannot be calculated for Hispanic youths because data for this ethnic group are not broken out in the UCR or other systematic data collection sys tems (Soriano, 1998). A few regional and city studies suggest that homicide arrest rates for Hispanic males are substantially higher than those for non-Hispanic white males and that African American males typical ly have the highest rates (Prothrow-Stith & Weissman, 1991;Smith et al., 1988;Sommers & Baskin, 1992;Zahn, 1988). The difference between homicide arrests of Hispanic and non-Hispanic white youths is sub stantial in these studies, but it is not as great as the dif ference between African American and white youths. The existence of much larger racial and ethnic dif ferences in arrest rates than in self-reported violence is a matter of great concern. On the one hand, there is no reason to expect similar distributions, because these measures were designed to assess different aspects of violence. But if both measures are valid and reliable, the discrepancy suggests that the probability of being arrested for a violent offense varies with race/ethnici ty. Explanations for this discrepancy focus on selective reporting of offenses to the police, different patterns of police surveillance, racial/ethnic biases in self-report measures, and racial/ethnic bias on the part of police, victims, and witnesses. Some studies have explored these explanations, but their findings are not definitive (Austin & Allen, 2000;Blumstein et al., 1986;Hawkins et al., 1998;Sampson & Lauritsen, 1997). This complex issue will also be discussed in Chapter 3, which considers other dimension's of violent offending.
Arrest ratios of Native American" to white youths are similar, except for the homicide ratio in 1998. Similarly, arrest rates of Asian Americans for homicide and robbery differ little from those of whites, but at least two whites are arrested on charges of rape or aggravated assault for every Asian American. Possible reasons for these differences have not been well studied.
In sum, racial and ethnic differences in rates of violence are greater in arrest statistics than in self reports of violent behavior. The reasons are not well understood, with conflicting evidence from various studies. Self-reports and arrest records produce simi lar estimates of trends in violence by sex: Violent behavior still occurs more often among male than female youths, but the gap has been narrowing.

# V io l e n c e a t Sc h o o l
Recent shootings at schools have galvanized public concern about school safety, but studies described here find that schools nationwide are relatively safe. In contrast to public perceptions, schools have fewer homicides and nonfatal injuries than homes and neighborhoods. However, some students are at greater risk of being killed or injured at school than othersspecifically, senior high school students from racial or ethnic minorities who attend schools in urban districts (Kachur et al., 1996).

# Homicides and Nonfatal Injuries
Two nationwide studies of school homicides have been conducted by the Centers for Disease Control and Prevention in collaboration with the U.S. Departments " The 1998 arrest rate was atypically high for the 1993-1999 period. This rate was tw ice the rate for every other year over this period and ^-'"p e a rs to be an anomaly.
-f Education and Justice. The first study covered a 2year period from July 1992 through June 1994 and identified 68 students who were killed on or near school grounds or at school-related events (Kachur et al., 1996). Most of the victims were male and were killed with a firearm. These homicides represent less than 1 percent of all youth homicides in the period studied, and the estimated incidence of school-associated vio lent death was 0.09 per 100,000 student-years.12 Those at greatest risk of being killed were from racial or eth nic minorities, from senior high schools, and from urban school districts. The homicide rate in urban schools, for example, was nine times greater than the rate in rural schools. Most offenders and victims alike were male, under age 20, and from a racial or ethnic minority. The most common motives were an interper sonal dispute or gang-related activities.
The second study, using the same methodology, updated the figures through June 1999 (CDC, 2000a). It identified 177 students age 5 to 19 who were killed in this 5-year period; the vast majority of the homi cides (84 percent) involved firearms. School-associat ed homicides remained at less than 1 percent of all homicides among students, but the frequency of homi cides involving more than one victim increased. The three school years from August 1995 through June 1998 saw an average of five multiple-victim homi cides or homicide-suicides per year. An average of one such event occurred in each of the 3 years from August 1992 through July 1995.
Thus, trends throughout the 1990s show that the number of school homicides has been declining. Yet within this overall trend, homicides involving more than one victim appear to have been increasing.
In regard to nonfatal injuries at school, the National Crime Victimization Survey found in 1998 that the rate of serious violent crimes against youths age 12 to 18 was one-half as great when they were at school as when they were not. At school, the highest victimization rates were among male students and younger students (age 12 to 14) (Kaufman et al., 2000). The rate was highest in urban schools in 1992, but by 1998 the rates at urban, suburban, and rural schools were similar. Overall, cr Q between 1992 and 1998, the rate of serious violent crimes at school remained relatively stable at about 8 to 13 per 1,000 students (Kaufman et al., 2000).
The stability of this trend is corroborated by the MTF survey, which asks high school seniors whether they have been victims of violence. The percentage of seniors reporting that they had been injured with a weapon at school remained stable at about 5 percent from 1976 to 1998 (Flanagan & Maguire, 1992;Maguire & Pastore, 1999) (Figure 2-9). The same vic timization rate is reported by the National Study of Delinquency Prevention in Schools for 1998 (Gottfredson et al., 2000). However, the MTF trend masks large fluctuations in victimization reported by African American students (Figure 2-9). From 1980 to 1998, between 4 ( 2.8) and 13 ( 3.6) percent of African American students reported having been injured with a weapon at school.

# Weapons at School
Recent findings regarding students carrying weapons (a gun, knife, or club, for example) at school are encouraging. In 1999, the Youth Risk Behavior Survey (YRBS) found that about 7 percent of all high school students reported carrying a weapon on school proper ty within the last 30 days (Kann et al., 2000) (Figure 2-5). In 1993, almost 12 percent of high school stu dents reported carrying a weapon at school in the last 30 days (Kann et al., 1995), a 42 percent decrease Kann et al., 2000). A somewhat less pronounced decline was apparent among high school seniors in the MTF survey (Kaufman et al., 1998). Both studies found the problem to be of rough ly the same magnitude: In 1995, about 6 to 8 percent of 12th graders reported carrying a weapon at school at least once during the past month.
Evidence of an upsurge in the number of students carrying weapons at school before 1993 is less clear. The YRBS first asked this question in 1993, and the MTF did not ask until the 1990s. Nonetheless, smaller or less representative studies suggest a substantial increase in weapon carrying between the 1980s and the early 1990s (reviewed in Elliott et al., 1998). Entries are 3-year running averages of the percentage of 12th graders who reported that someone had injured them with a weapon at school during the past 12 months. Examples of weapons are knives, guns, and clubs. "At school" means inside or outside the school building or on a school bus. 95% confidence intervals for total sample and whites are less than  1.5%; for African Americans, less than  4.6%.

# Perceptions of School Violence
Although the overall risk of violence and injury at school has not changed substantially over the past 20 years, both students and their parents report being increasingly apprehensive about their schools. Studies reveal that, during the early 1990s, students grew more fearful about being attacked or harmed at school and that they were avoiding certain places within their schools (Kaufman et al., 1998). By 1999, these fears had subsided somewhat (Kaufman et al., 2000), but parents still say they are afraid for their children at school. A recent Gallup poll found that nearly half of the parents surveyed feared for their children's safety when they sent them off to school, whereas only 24 percent of parents reported this concern in 1977 (Gallup, 1999a). In May 1999, shortly after the shoot ings at Columbine High School in Littleton, Colorado, 74 percent of parents said that a school shooting was very likely or somewhat likely to happen in their com munity (Gallup, 1999b).
O Public perceptions about school safety seem at odds with the evidence that the risk for serious violence at school has not changed substantially over the past 20 years. But several indicators of violence did increase during the epidemic-school fights, gangs, drug use, and students carrying weapons to school. While gangs and weapon carrying have declined recently, the rates of drug use and physical fighting are high and have not changed between 1991between and 1999between (Brenner et al., 1999). Today's school bullies are still more likely to be carry ing guns than those of the early 1980s, and the propor tion of students reporting that they felt too unsafe to go to school has not changed since the peak of the violence epidemic in the mid-1990s. These findings add to the concern that the violence epidemic is not yet over.

# G a n g s a n d V io l e n c e
Gang members, a relatively small proportion of the adolescent population, commit the majority of serious youth violence (see Spergel, 1990, for a review). In two major longitudinal studies in Denver and Rochester (discussed in more detail in Chapter 3), 14 to 30 percent of the youths surveyed were gang mem bers at some time during the study, and they account ed for 68 to 79 percent of the serious violence report ed . Similar findings have been reported in other studies using nonrandomized local samples (Battin et al., 1996;Fagan, 1990). In Rochester, 66 percent of chronic violent offenders were in gangs .
A high proportion of gang members are also involved in drug sales and possessing/carrying a gun, two behaviors closely linked to serious violence. The 1999 National Youth Gang Survey (a national survey of law enforcement agencies) estimates that 46 percent of youth gang members are involved in street drug sales (Egley, 2000). In the Rochester study, 67 percent of youths reporting they owned/carried a gun for pro tection were gang members and 32 percent reported they sold drugs. Only 3 to 7 percent of non-gun own ers or sport gun owners were involved in drug selling. Further, 85 percent of youths who owned guns for pro tection were involved with peers who owned guns for protection .
Rates of . violence are higher in schools where gangs are present. The rate of victimization in schools with gangs is 7.5 percent, compared to 2.7 percent in schools without gangs . Gangs are present not only in inner-city schools, but in many suburban and rural schools as well. Between 1989 and 1995, the proportion of students reporting gangs at their school increased from 15 percent to 28 percent . By 1999, how ever, that figure had dropped to 17 percent (Kaufman et al., 2000). A decline in the number of gangs in U.S. schools between 1996 and 1997 has also been report ed by law enforcement agencies (National Youth Gang Center, 1999).
The National Youth Gang Survey reported more than 26,000 active youth gangs in schools and com munities in 1999, down 15 percent from 1996 (Egley, 2000). Yet the same survey reported more than 840,500 active gang members in 1999, a decline of less than 1 percent from the peak level in 1996. Thus, from this source, it appears that the number of youths actively involved in gangs remains very high.
The racial/ethnic composition of gangs in 1999 was 47 percent Hispanic, 31 percent African American, 13 percent non-Hispanic white, and 7 per cent Asian. These rates have been relatively constant since 1990.
In 1998, 92 percent of all gang members were male (National Youth Gang Center, 2000), although some evidence indicated that girls' involvement in gangs increased during the epidemic (Chesney-Lind et al., 1996;Chesney-Lind & Brown, 1999;. However, the National Youth Gang Survey reports a decline in female membership, with less than 2 percent of gangs nationwide reporting pre dominantly female membership.

# C o n c l u s io n s
The United States suffered an epidemic of violence in the decade from about 1983 to 1993. Arrest rates of young people for homicide and other violent crimes skyrocketed. Several other violence indicators con firmed an epidemic of violence during that period.
There are three factors that appear to play a sig nificant role in this dramatic surge in lethal violence or injury: gangs, drugs, and guns. The combination of increased involvement in gangs, selling drugs on the street, and carrying guns for protection had lethal implications. And it was African American and Hispanic males who were disproportionately caught up in this set of circumstances.
After 1993/1994, arrests and victims' reports of violence began to decline, returning in 1999 to rates only slightly higher than those in 1983. These declines come as welcome news. Yet several other leading indicators of violence remain high. Young people's self-reports of violence have not declined at all. Arrest rates for aggravated assault remain quite high. Some estimates of gang membership indicate that this prob lem remains close to levels at the peak of the epidem ic. Indeed, self-reported violent behavior is at least as high today as it was in 1993. Why has this important indicator of violence remained high while other indi cators have come down?
A major reason is firearms usage. It is now clear that the violence epidemic was caused largely by an upsurge in the use of firearms by young people. Ready access to firearms during a violent confrontation often had grievous consequences. Youth violence became more lethal, resulting in dramatically higher rates of homicide and serious injury. This triggered reporting to and response from police, leading to higher rates of arrest. Although firearm usage may not cause vio lence, it clearly increases the severity of violence.
Today's youth violence is less lethal, largely because of a decline in the use of firearms. Fewer young people today are carrying weapons, including guns, and fewer are taking them to school. Homicides at school are declining. Violent confrontations are less likely to result in killing or serious injury, and the police are less likely to be called in for an arrest. This is a heartening trend, but this is not the time for complacency. Violent behavior is just as prevalent today as it was during the violence epidemic. Some 10 to 15 percent of high school seniors reveal in confi dential surveys that they have committed at least one act of serious violence in the past year. This prevalence rate has been slowly yet steadily rising since 1980.
There is also a difference by sex in the volume of violence. Male youths commit many more violent acts than female youths, according to both arrest records and self-reports. The existence of a racial difference between African American and white youths is more questionable. Arrest records indicate that many more African American than white youths commit violent crimes, whereas self-reports indicate much smaller racial differences in incident rates and nonexistent dif ferences in prevalence rates. The disparities between these two indicators of violence have not been satis factorily investigated, and more research on them is clearly warranted.
Looking at all self-reported violent behavior, it is apparent that youth violence still poses a serious pub lic health problem. Should firearms once again become appealing and accessible to young people, the potential for a recurrence of the violence epidemic is quite real. The magnitude of serious violence occurring beneath the police radar should warn us that youth violence is ^'sistent problem demanding a focus on prevention.

# M
-st violence begins in the second decade of life. This chapter looks closely at childhood and adolescence as critical periods of development to trace how violence unfolds-its onset, duration, and t continuity into adulthood. It also examines violence in relation to other risky behaviors that emerge in adolescence.
The dynamics of youth violence are best under stood from a developmental perspective, which recog nizes that patterns of behavior change over the life course. Adolescence is a time of tumultuous change and vulnerability, which can include an increase in the frequency and means of expression of violence and other risky behaviors. Understanding when and under what circumstances violent behavior typically occurs helps researchers craft interventions that target those critical points in development.
Our understanding of developmental patterns de pends in large part on longitudinal studies, which track the same group of individuals over long periods of time, sometimes a decade or more. Four major longitu dinal studies are described in this chapter. They add new dimensions to the surveillance statistics presented in Chapter 2, and they provide essential background for Chapter 4, which deals with why young people become involved in violence.

# Ea r l ya n d La t e -O n s e t T r a je c t o r ie s
Longitudinal research has detected two prominent developmental trajectories for the emergence of youth violence, one characterized by an early onset of violence and one by a late onset. Children who com mit their first serious violent act before puberty are in the early-onset group, whereas youths who do not become violent until adolesence are in the late-onset group. While other developmental trajectories have been identified (D'Unger et al., 1998;, this report focuses on the early-and late-onset trajectories because they are recognized by most researchers, they debunk the myth that all seri ous violent offenders can be identified in early child hood, and they have strikingly different implications for prevention.
In the early-onset trajectory, problem behavior that begins in early childhood gradually escalates to more violent behavior, culminating in serious violence before adolescence. A child's first serious violent act may have been officially recorded, or it may have been reported by the child to researchers in a confi dential survey. The early-onset group, in contrast to the late-onset group, is characterized by higher rates of offending and more serious offenses in adoles cence, as well as by greater persistence of violence from adolescence into adulthood (reviewed in Tolan &Gorman-Smith, 1998). The National Youth Survey shows that nearly 13 percent of male adolescents in the early-onset tra jectory engaged in violence for two or more years, compared to only 2.5 percent in the late-onset trajec tory (Tolan & Gorman-Smith, 1998).
Between 20 and 45 percent of boys who are seri ous violent offenders by age 16 or 17 initiated their violence in childhood (D'Unger et al., 1998;Elliott et al., 1986;. A higher percentage of girls who were serious violent offenders by age 16 or 17 (45 to 69 percent) were violent in childhood (Elliott et al., 1986;. This means that most violent youths' begin their violent behavior during adolescence. However, the youths who commit most of the violent acts, who commit the most serious violent acts, and who continue their violent behavior beyond adolescence begin during childhood Moffitt, 1993;Tolan, 1987;Tolan & Gorman-Smith, 1998).
The greater prevalence of late-onset youth vio lence refutes the myth that all serious violent offend ers can be identified in early childhood. In fact, the majority of young people who become violent show little or no evidence of childhood behavioral disor ders, high levels of aggression, or problem behav iors-all predictors of later violence.
The implications of these findings for prevention are clear: Programs are needed to address both earlyand late-onset violence. Targeting prevention programs solely to younger children with problem behavior miss es over half of the children who will eventually become serious violent offenders, although universal prevention programs in childhood may be effective in preventing late-onset violence (see Chapters 4 and 6).

# O n s e t a n d Pr e v a l e n c e o f S e r io u s V io l e n c e
Much of what is known about the onset, prevalence, and other characteristics of serious violence during the adolescent years comes from four important longitu dinal surveys. The only nationally representative one is the National Youth Survey (NYS), an ongoing study of 1,725 youths age 11 to 17 in 1976, when the survey began (Elliott, 1994). These youths have been tracked by researchers for more than two decades and through nine waves, or points at which they were interviewed and/or their official records were sought to corrobo rate self-reported violence.2
The other three longitudinal studies cited here are city surveys sponsored by the U.S. Office of Juvenile Justice and Delinquency Prevention and the National Institutes of Health Thornberry et al., 1995).3 Beginning in 1988, three teams of researchers began to interview 4,500 youths age 7 to 15 in three cities-Denver, Pittsburgh, and Rochester (New York). These youths were monitored at different points from 1988 to 1994. Each sample disproportion ately represents youths at high risk of delinquency to ensure that it is large enough to draw valid conclu sions about delinquency and violence, but each also uses weighting procedures to yield locally representa tive estimates. The estimates presented here are based on weighted data.
These four surveys define serious violence as aggravated assault, robbery, gang fights, or rape; an individual is labeled a serious violent offender if he or she reports committing any one or more of these offenses.4 Gang fights are included because follow-up information on these fights reveals that most of them involve injury serious enough to require medical attention (Elliott, 1994).
Only the NYS reports the hazard rate for serious violence during the first two decades of life.5 The haz ard rate is the proportion of persons who initiate seri ous violence at a given age. Serious violence begins mostly between the ages of 12 and 20 (Figure 3-1). In fact, 85 percent of people who become involved in serious violence by age 27 report that their first act occurred between age 12 and 20. The onset of serious violence is negligible after age 23 and before age 10 (only 0.2 percent of arrests for serious violent crime in 1997 involved a child under age 10 ).
The peak age of onset is 16, when about 5 percent of male adolescents report their first act of serious vio lence. The age of onset peaks somewhat later for
The Developmental D ynam ics of Youth Violence somewhat by race/ethnicity. It is lower for white males (5 percent) than for African American males (8 percent) (Elliott, 2000a). A similar finding is reported in the Pittsburgh Youth Survey .6 No comparable hazard rates have been pub lished for female youths, but other studies have found that they are generally lower.7
Age-specific prevalence-that is, the proportion of youths at any given age who report having com mitted at least one serious violent act-is also greatest in the second decade of life. The NYS and the three city surveys find that, broadly speaking, age-specific prevalence among male youths ranges from about 8 to 20 percent between the ages of 12 and 20 (Figure 3-2). Among females, it ranges from 1 to 18 percent (Table 3-1). There is some variability across surveys, however. In general, the NYS has lower rates than the three city surveys, reflecting the difference between a national sample and local samples drawn from urban 1986, whereas the three city surveys cover the years 1986 or 1988 to 1994, the peak years of the violence epidemic (see Chapter 2). Nevertheless, the estimates for age 17 across these longitudinal surveys are in the same range as those for high school seniors in the Monitoring the Future survey (see Chapter 2).
Another key difference between the national and city surveys is the maturation effect, or the age at which serious violence begins to decline sharply dur ing the transition to adulthood. The NYS shows a decline in age-specific prevalence starting in the late teen years and a steep drop-off by age 20. In contrast, the city surveys, which were begun more recently, do not show a decline in the late teen years , and they have not yet published data on prevalence in early adulthood. Therefore, it is too soon to tell whether or at what age more recent groups of youths will mature out of violence. It is possible that young people are staying violent longer.  Some important differences in age-specific preva lence by sex have emerged from the data (Table 3-1). Female adolescents have lower rates of serious vio lence throughout the second decade. For the NYS and Denver surveys, rates at age 12 are about twice as high for boys as for girls. Between age 12 and 15 in Rochester, the rates are fairly similar. For all studies, the rates for females at age 17 are about one-quarter the rates for males. In addition, the peak age of seri ous violent offending occurs a few years earlier among females, and their maturation out of serious violence is both earlier and steeper than males'.
Age-specific prevalence also varies by race/eth nicity (Table 3-1). The NYS finds a significant racial gap between ages and 17, when rates for African  .BEST COPY .AVAILABLE American youths are 36 to 50 percent higher than those for white youths. The city surveys show an even wider gap between African American and white youths . Rates among Hispanic youths, reported only for Denver and Rochester, are similar to or lower than those reported by African American youths in these cities. The prevalence reported by Hispanic youths ranges from 6 to 12 per cent in Denver and about 10 to 20 percent in Rochester. Possible reasons for developmental differ ences by sex, race, and ethnicity are discussed in Chapter 4. None of these comparisons takes into account the effects of poverty, education, housing, or other environmental conditions.

# C u m u l a t iv e P r e v a l e n c e
Figure 3-2. Prevalence of serious violence among male youths, by age: four longitudinal surveys youths, the NYS shows it rising to about 40 percent and then leveling off beyond age 22. In the city sur veys, it reaches more than 40 percent of male and 32 percent of female youths by age 17. Not only is the rise in cumulative prevalence by age 17 steeper in the city surveys, the magnitude is substantially higher.
These differences between a nationally representa tive sample and city samples are to be expected. The timing of the surveys may also explain some of the dif ferences. For example, 17-year-olds in the NYS were interviewed at some point between 1976 and 1982, whereas 17-year-olds in the city surveys were inter viewed at some point between 1988 and 1994, the era during which the self-reported prevalence of serious youth violence increased somewhat (see Chapter 2).
There is a pronounced difference in cumulative prevalence by sex. Among I7-year-olds, the Denver Cumulative prevalence refers to the proportion of youths at any particular age who have ever commit ted a serious violent offense.8 As a measure of vio lence, it tends to equalize rather than magnify differ ences across populations because it counts youths only once, regardless of when or how often they engaged in violent acts.
The most striking feature of the cumulative preva lence is its sheer magnitude: About 30 to 40 percent of male and 16 to 32 percent of female youths have com mitted a serious violent offense by age 17 (Figure 3-3). Although these rates are only slightly higher than those found in international studies, they repre sent a more serious set of offenses (Junger-Tas et al., 1994).
The cumulative prevalence of youth violence is generally consistent across the four surveys. For male Cum ulative prevalence is also known as lifetim e prevalence or ever-prevalence to a given age. Confidence intervals are as follows: NYS African American males = .45 ( 9.8); NYS white males = .38 ( 3.9); RYDS males = .40 ( 3.7); DYS males = .43 ( 3.6); PYS males = .44 ( 2.6); RYDS females = .32 ( 6.1); DYS females = .16 ( 2.8).
survey found a cumulative prevalence of 16 percent for female youths and 43 percent for male youths, whereas the Rochester survey showed 32 percent and 40 percent, respectively. Data on cumulative preva lence for females are not available in the Pittsburgh survey or the NYS.9
On the other hand, there are few differences in cumulative prevalence by race over the teen years, according to the NYS. By age 23, white males had a cumulative prevalence of 38 percent and African American males had a cumulative prevalence of 45 percent, a difference that is not statistically significant (Figure 3-3).

# Ra t e s o f O f f e n d in g a n d V io l e n t C a r e e r s
Violent youths commit a remarkably high number of crimes (Tolan & Gorman-Smith, 1998). An analysis of NYS data shows that these young people (both male and female) averaged 15.6 rapes, robberies, aggravated assaults, or some combination of these crimes over a 16-year period (1976 to 1992) (Elliott, 2000b). W hat's more, they averaged just over six serious violent offenses each during the years in which they were active (Elliott, 2000b).10 This mean annual rate of offending is similar to rates reported in the three city surveys for males (about 5 to 9 seri ous violent offenses per year)  but much higher than the rates for females (2 to 4.5 per year).
It is noteworthy that the mean annual rate of indi vidual offending appears to be essentially unchanged over the past two decades. This finding is corroborat ed by a study of trends among juvenile offenders processed by a county court system in Arizona (Snyder, 1998) and by an analysis of both National Crime Victimization Survey data and arrest records (Snyder & Sickmund, 2000). Finally, the Monitoring the Future survey (see Chapter 2) found no significant changes in individual offending rates for robbery or assault with injury between 1983 and 1993."
Career length has been variously defined as the number of years of active offending, the maximum number of consecutive years, or the span between the first and last year during which a young person meets the criteria for a serious violent offender (Blumstein et al., 1986). There are relatively few estimates of vio lent career lengths. In the NYS, the mean career length (number of years of active violent offending) was 2.6 years. The most frequent career length was 1 year (36.8 percent of serious violent offenders). Three-quarters of these serious violent youths had careers lasting 3 years or less, and 15 percent had careers of 5 years or more (Elliott, 2000b). Based on 5 years of data, the Denver survey reports that 42 per cent of serious violent youths were active for only 1 year, 22 percent for 2 years, and 31 percent for 3 or more years .
The typical violent career comprises either a single year of continuous offending or a longer period of inter mittent offending. Relatively few violent careers are characterized by years of uninterrupted violence. In Denver, well over half of the careers that lasted three or more years had at least one year with no violent offend ing; three-quarters of those that spanned a 5-year period had an intermittent pattern of offending . Evidence that most careers lasting more than 1 year were characterized by intermittent offending also surfaced in the NYS (Elliott et al., 1986). This intermit tent pattern makes it difficult to identify serious violent offenders with cross-sectional studies or with longitudi nal studies that have long periods between data collec tion .
In sum, these studies suggest that in most cases vio lent careers are relatively short and are characterized by intermittent offending. During active periods, however, most careers are marked by a high rate of violent offending-up to 10 offenses per year (Elliott et al., 1986;.

# D e v e l o p m e n t a l Pa t h w a y T o V io l e n c e
Violent youths do not usually begin their careers with a serious violent offense. While the developmental path way varies, depending on what types of behavior are monitored, studies generally agree that a violent career begins with relatively minor forms of antisocial or delinquent behavior. These acts later increase in fre quency, seriousness, and variety, often progressing to serious violent behavior (Elliott, 1994;Moffitt, 1993;Tolan & Gorman-Smith, 1998). Several complex pathways to serious violence have been proposed (Loeber, 1996;Elliott, 1994).
The NYS suggests that violence escalates over time. Most serious violent youths who engage in multiple types of violent behavior begin with aggravated assault, then add a robbery, and finally a rape. (Rape appears to be the end point of the progression, although there were not enough homicides in the NYS sample to include homicide in the analysis.) Robbery precedes rape in over 70 percent of cases in which both acts have been reported, and about 15 percent of serious violent offenders in the NYS reported having committed a rape (Elliott, 1994(Elliott, , 2000a. This sequence must be considered tentative because it is based on a single study.
When serious violence becomes part of a youth's repertoire of antisocial behavior, it does not substitute for less serious forms of violence; rather, it adds to them and escalates the overall frequency of violent acts. Thus, serious violent youths are high-frequency offend ers who are involved in many less serious as well as serious offenses. These youths account for a major share of all criminal behavior, a pattern that is explored more fully in the next section.
11 Calculations were done by the senior scientific editor Elliott on the basis o f M onitoring the Future prevalence and frequency data on aggra vated assault and robbery contained in the 1991 and 1998 Sourcebooks o f Criminal Justice Statistics (Flanagan & Maguire, 1992;Maguire & Pastore, 1999). Individual offending rates are based on estimated incident rates. For this calculation, frequencies associated w ith categorical scores were as follows: not at all = 0; once = 1; tw ice = 2; 3 or 4 times = 3.5; and 5 or more times = 5. Individual offending rates for robbery in both 1983 and 1993 were 1.8. Rates for assault w ith injury were 2.3 and 2.6 (not significant). The mean individual offending rate can remain relatively constant despite increases in prevalence and incident rates noted in Chapter 2.

# C h r o n ic V io l e n t O f f e n d e r s
A minority of serious violent youths are responsible for the overwhelming majority of serious violent crime, a finding supported by numerous self-report and arrest studies (Tolan & Gorman-Smith, 1998;Tracy & Kempf-Leonard, 1996). In the city surveys, chronic offenders, though representing less than 20 percent of all serious violent offenders; accounted for 75 to 80 per cent of self-reported violent crimes . NYS data yield similar findings: Chronic offenders (youths with three or more violent offenses) accounted for 76 percent of all felony assaults and 89 percent of all robberies reported by offenders in 1980 . Chronic violent youths may also account for a dis proportionate share of all youth crime. The NYS reveals that in 1980 these serious violent offenders accounted for 79 percent of all felony theft, 66 percent of all illegal services (primarily drug selling), and 50 percent of all self-reported crime . In the Philadelphia Birth Cohort Study, 15 percent of youthful offenders accounted for 74 percent of all offi cial crime (Tracy & Kempf-Leonard, 1996).
As noted earlier, youths whose violence begins before puberty are more likely to become chronic vio lent offenders . In the Rochester survey, 39 percent of children who initiated violent behavior by age 9 eventually became chronic offenders, 30 percent of those who initiated violence between the ages of 10 and 12 became chronic offenders, and 23 percent of those who initiated violence after age 13 became chronic violent offenders. In Denver, 62 per cent of those initiating violence by age 9 and 48 percent of those initiating violence between 10 and 12 became chronic violent offenders. Looking at this another way, 55 percent of all chronic violent offenders in Denver came from the early-onset trajectory . While the late-onset trajectory involves a sub stantially larger group of youths, fewer than half of all chronic offenders come from this group.
Although most chronic violent offenders in the three city surveys (62 to 77 percent) eventually had contact with the police for some offense (though not necessarily a violent offense), one-quarter to one-third 0 were never arrested . Among those who were arrested for some offense, the first con tact came well after they had begun their violent careers. Interventions by the justice system occur too late to prevent such youths from escalating from less serious offenses to serious violence. Fortunately, it appears that at least half of chronic violent offenders can be identified as being at risk in childhood.
Research has found a powerful relationship between membership in a gang and chronic involve ment in serious violence (see review in . As noted earlier (see Chapter 2), gang members, a relatively small proportion of the adolescent popula tion, commit the majority of serious youth violence (see Spergel, 1990, andThomberry, 1998, for reviews).

# S u p e r p r e d a t o r s ?
Between 1983 and 1993, adolescents were committing homicide at dramatically higher rates than in previous years (see Chapter 2). Did those youths represent a new breed of frequent, vicious, remorseless killers? Did the character of violent youths change during that time-and is it still different today (Bennett et al., 1996)? The answer seems to be no, for several reasons.
First, the increase in homicides was similar across all age groups (see Chapter 2). This suggests that it resulted from a relatively sudden change in the envi ronment that affected all youths rather than from a gradual change in the socialization process, which would have led to progressively more vicious youths with each succeeding age group. Second, the increase in homicides was highly specific to certain youthsnamely, African American males (Zimring, 1998); moreover, it did not take place among females (see Chapter 2). Third, during the violence epidemic, there was a decline in family members killed by youths .
Fourth, a new breed of superpredators should have resulted in more burglaries, auto thefts, and lar cenies, but no such increases occurred . It should also have resulted in more homicides involving knives and other weapons, but this did not occur (Zimring, 1998). Fifth, there was no evidence that individual rates of serious violent crime changed during the epidemic. More youths were involved, but the average number of offenses committed by each did not change. Finally, there may be anecdotal evidence that today's youths show less remorse for their violence, but this has not been substantiated by research.
In sum, the epidemic of violence from 1983 to 1993 does not seem to have resulted from a basic change in the offending rates and viciousness of young offenders. Rather, it resulted primarily from a relative ly sudden change in the social environment-the intro duction of guns into violent exchanges among youths. The violence epidemic was, in essence, the result of a change in the presence and type of weapon used, which increased the lethality of violent incidents (Wintemute, 2000).

# C o -O c c u r r in g Pr o b l e m B e h a v io r s
Serious violence is accompanied by a wide range of other problem behaviors, including property crimes, substance use, gun ownership, dropping out of school, early sexual activity, and reckless driving. The co occurrence of these problem behaviors has been borne out by numerous national - and local studies (see reviews in Elliott, 1993;Huizinga & Jakob-Chen, 1998;Tolan & Gorman-Smith, 1998).
The overlap is greatest between serious violence and other forms of crime. In the three city surveys, 82 to 92 percent of chronic violent youths were involved in property crimes, 71 to 82 percent in public disorder crimes, and 26 to 45 percent in selling drugs . Very similar rates were found in the NYS . Rates of co-occur rence were much higher among serious violent youths than among less violent youths.
Substance use and abuse are a central feature of a violent lifestyle (Dembo et al., 1991;Elliott, 1994;Johnson et al., 1991). In the Denver survey, for example, about 58 percent of serious vio lent offenders were alcohol users and 34 percent were marijuana users. The prevalence and frequen cy of use were much lower in youths who were not seriously violent (Huizinga & Jakob-Chen, 1998).
The NYS indicates that 94 percent of serious violent youths in 1980 were using alcohol, 85 percent were using marijuana, and 55 percent were using several illicit drugs. Over half (55 percent) were abusing drugs-that is, they reported health or relationship - problems, or both, associated with their drug use .
Similar findings regarding the overlap of sub stance use and serious violence hold for the Rochester study (Thornberry et al., 1995). Moreover, chronic violent youths in Rochester and violent youths in the NYS had higher rates of dropping out of school, gun ownership and use, teenage sexual activity and par enthood, tobacco use, driving under the influence of alcohol or drugs, and gang membership than nonseri ous offenders or nonoffenders (Elliott, 1993;Thornberry et al., 1995).
In sum, these studies show that a sizable propor tion of serious violent youths have co-occurring problem behaviors-and at rates significantly higher than those of their less violent counterparts. However, by no means all serious violent youths or even all chronic violent youths have co-occurring problems. Moreover, not all youths with problem behaviors are seriously violent. The fact that serious violence and problem behaviors tend to occur together does not necessarily mean that one causes the other (see Chapter 4) (Elliott, 1993;.

# Violence and Mental Health
The relationship between violence and mental health has been studied more intensively in adults than in young people. An earlier U.S. Surgeon General's report on mental health, after weighing the evidence, empha sized that the contribution of mental disorders to over all violence in the United States is very small. In fact, public fear is out of proportion to the actual risk of vio lence, which contributes to the stigmatizing of people with severe mental disorders (Link et al., 1999). Even though the risk of violence is low overall, it is greatest for adults with serious mental disorders who also abuse substances (Steadman et al., 1998;Swanson, 1994).
Although violence is relatively widespread among adolescents, few studies have been undertaken on the co-occurrence of violence and mental health problems or disorders among U.S. adolescents. Such popula tion-based studies are important because they avoid the bias inherent in surveying hospitalized patients or convicted offenders.
Both the NYS and the Denver survey examine the co-occurrence of serious violence and mental health problems. In the NYS, 28 percent of serious offenders age 11 to 17 were classified as having men tal health problems, compared to 13 to 14 percent of nonserious delinquent youths and 9 percent of nonof fenders. Youths were classified as having mental health problems on the basis of their responses to questions about emotional problems, social isolation, and feelings of loneliness . (The questions were not designed to arrive at a diagnosis of a mental disorder.) Serious violent offenders were more likely than either nonserious offenders or nonoffenders to report having these types of mental health problems.
In the Denver study, serious violent youths were found to have higher rates of psychological problems, based on parents' responses to the Child Behavior Checklist (Achenbach & Edelbrock, 1983). These problems included externalizing and internalizing behavior, depression, uncommunicativeness, obses sive-compulsive behavior, hyperactivity, social with drawal, and aggressiveness. The rates at which most of these problems occurred in serious offenders were no different from the rates at which they occurred in nonviolent delinquent youths; however, rates in non delinquent youths were lower. Thus, delinquent youths in general were more likely to have psycho logical problems than nondelinquent youths (Huizinga & Jakob-Chen, 1998).
Two problems were linked directly to violent behavior-externalizing symptoms and aggressive behavior. Approximately half of all serious violent offenders display these problems, although the link with externalizing behaviors is statistically significant only for boys. In addition, parents of violent offenders report seeking help for mental health problems more often than parents of nondelinquent or nonviolent delinquent youths. These parents did not go to mental health professionals or school counselors; rather, they sought the advice of friends, relatives, and spiritual leaders (ministers, rabbis, or priests). A similar finding is reported in the Pittsburgh study (Stouthamer-Loeber & Thomas, 1992).
The Denver study found no differences between the self-esteem of serious violent offenders and non violent offenders or nonoffenders (Huizinga & Jakob-Chen, 1998). In general, there is little evidence that low self-esteem causes violence or that violent offend ers have low self-esteem. On the contrary, the evi dence is more consistent with the position that high self-esteem and threats to high esteem lead to violence (Baumeister et al., 1996). This has important implica tions for treatment and intervention programs and the use of esteem-building activities in these programs.
A population-based study in New Zealand found that in young adulthood (age 21), serious violent offenders are more likely than nonoffenders to exhib it substance dependence disorders, schizophreniaspectrum disorders,12 or both (Arseneault et al., 2000). These New Zealand findings are consistent with the studies of U.S. adults showing that the greatest risk of violence stems from the combination of serious men tal disorder and substance dependence. However, about 10 percent of serious violent offenders13 in the New Zealand study exhibited schizophrenia-spectrum disorders without substance dependence or other psy chiatric conditions. The researchers concluded that while the contribution of serious mental illness to vio lence in young adults remains small, it may be slight ly higher than it is in adults. One possible reason for the difference is that the overwhelming majority of young adults with mental disorders in the New
The Developm ental Dynam ics of Youth Violence Zealand study had not been treated or hospitalized within the previous year.
Another recent community-based study found a link between personality disorders (a group of severe mental disorders) and violence. Adolescents with personality disorders,14 as determined by diagnostic interviews, were more likely than other adolescents to commit vio lent acts such as assault with injury and robbery (Johnson et al., 2000). For example, about 36 percent of adolescents with personality disorders versus 16 percent without the disorders committed a violent act against others15 during adolescence. The relationship between personality disorders and violence remained after taking many factors into account, including co-occurring depression, anxiety, and substance disorders. Only a few adolescents (13 percent) with personality disorders had received mental health services during the previous year (Johnston, personal communication, 2000).
Thus, there is some evidence of a relationship between serious mental disorders and violence in ado lescents or young adults in the general population. Young people with serious mental disorders may be at risk of becoming violent if they also abuse substances or if they have not received treatment for their mental disorder. More research .is needed to understand the relationship between serious youth violence and men tal illness.

# O f f e n d in g a n d V ic t im iz a t io n
Violent offenders are frequently victims of violence Lauritsen et al., 1991;Sampson & Lauritsen, 1990. Data from the NYS reveal that victimization is highest among African Americans, males, and frequent offenders (Lauritsen et al., 1991). In addition, youths who report abusing drugs and alcohol, hanging out with delin quent peers, and participating in social activities with little adult supervision are at greater risk of being vic tims of violence (Gottfredson, 1984;Lauritsen et al., 1991;Sampson & Lauritsen, 1990). A delinquent lifestyle greatly increases the likelihood of being a vic tim and appears to account for some of the disparities observed in offending and victimization by race/ethnicity and sex. The Denver survey shows that 42 per cent of serious violent offenders are also victims of violence (Huizinga & Jakob-Chen, 1998), with higher rates among male offenders than female offenders.
There are many reasons for the overlap between offending and victimization. Perhaps the most com mon is that the offender is injured by the intended tar get-either during the offense or later, in retaliation. Another reason is that offenders tend to live in more violent environments or their lifestyles take them into high-risk environments. The predictive relationship between victimization and offending, as well as the relationship with early child abuse, is discussed in Chapter 4.

# T r a n s it io n t o A d u l t h o o d
The transition from adolescence to adulthood features a fairly abrupt discontinuation of serious violence, at least according to the NYS. Rates of onset and agespecific prevalence show dramatic declines, and the cumulative prevalence levels off, as discussed above. Only about 20 percent of serious violent offenders continue their violent careers into their twenties (Elliott, 1994).
-While there are no differences by sex in the apparent termination of violent offending, there are significant differences by race. Twice as many African American as white youths continue their violent behavior into the adult years (Elliott, 1994). Preliminary analyses suggest that cessation of offend ing is related to having a stable job and a stable inti mate relationship.
By 1992, the most recent year for which data are available, many people monitored by the NYS had reached their late twenties and early thirties. There is virtually no published information about what patterns of violence may have continued into their adult years.
The more recent city surveys have published age-spe cific and cumulative prevalence findings only up to age 19, but these studies are still being conducted. Some evidence from these surveys (Figure 3-2) sug gests that violent careers are lasting longer, but addi tional waves of data are needed to verify this trend.
Understanding the demographics and dynamics of how patterns of serious violence change with the tran sition into adulthood is critical to designing programs that enhance the termination of violence.

# C o n c l u s io n s
The prevalence of serious violence by age 17 is star tling. About 30 to 40 percent of male and 15 to 30 per cent of female youths report having committed a seri ous violent offense at some point in their lives. This cumulative prevalence is similar among African American and white males, in contrast to other meas ures of violence, which show racial disparities (see Chapter 2).
Two general onset trajectories emerge from longi tudinal studies of youth violence-an early-onset tra jectory that begins before puberty and a late-onset one that begins in adolescence. Youths in the early-onset trajectory generally commit more crimes, and more serious crimes, for a longer time. These young people exhibit a pattern of escalating violence through child hood and adolescence, and frequently into adulthood.
Most youths who become violent, however, begin in adolescence. Their late-onset offending is usually limited to a short period, peaking at about age 16 and dropping off dramatically by age 20. They typically show few signs in childhood that they will become violent later on, laying to rest the myth that all violent adolescents can be identified in childhood.
The rate of individual offending appears to have remained virtually unchanged, both during and since the years of the violence epidemic, which began in 1983 and peaked in 1993. This finding, together with evidence that the epidemic was specific to gun-related violence, challenges the myth that the early 1990s produced a generation of superpredators who were - more vicious and who committed dramatically more crimes than earlier generations of young people. At the same time, the finding of a stable individual offending rate indicates that the violence epidemic has not altogether subsided.
Serious violence is frequently part of a lifestyle that includes drugs, guns, precocious sex, and other risky behaviors. Youths involved in serious violence typically commit many other types of crimes and exhibit other problem behaviors, presenting a serious challenge to intervention efforts. Successful interven tions must confront not only the violent behavior of these young people, but also their lifestyles, which are teeming with risk.
Prevention and intervention programs must also take into account the different patterns of violence typical of the early-and late-onset trajectories, as well as the relatively constant rates of individual offending. Early childhood programs that target at-risk children and families are critical for preventing the onset of a chronic violent career, but programs must also be developed to combat late-onset violence. The impor tance of late-onset violence prevention is neither widely recognized nor well understood. Substantial numbers of serious violent offenders emerge seeming ly without warning. A comprehensive community pre vention strategy must address both onset patterns and ferret out their respective causes and risk factors. But what do we know about why young people become involved in violence? Why do some youths get caught up in violence while others do not? There is no simple answer to these questions, but scientists have identified a number of things that put children and adolescents at risk of violent behavior and some things that seem to protect them from the effects of risk.

# In t r o d u c t io n t o R is k a n d Pr o t e c t iv e Fa c t o r s
The concepts of risk and protection are integral to public health. A risk factor is anything that increases the probability that a person will suffer harm. A pro tective factor is something that decreases the potential harmful effect of a risk factor. In the context of this report, risk factors increase the probability that a young person will become violent, while protective factors buffer the young person against those risks. The public health approach to youth violence involves identifying risk and protective factors, determining how they work, making the public aware of these findings, and designing programs to prevent or stop the violence.
Risk factors for violence are not static. Their pre dictive value changes depending on when they occur in a young person's development, in what social con text, and under what circumstances. Risk factors may be found in the individual, the environment, or the individual's ability to respond to the demands or requirements of the environment. Some factors come into play during childhood or even earlier, whereas others do not appear until adolescence. Some involve the family, others the neighborhood, the school, or the peer group. Some become less important as a person matures, while others persist throughout the life span. To complicate the picture even further, some factors may constitute risks during one stage of development but not another. Finally, the factors that predict the onset of violence are not necessarily the same as those that predict the continuation or cessation of violence.
Violence prevention and intervention efforts hinge on identifying risk and protective factors and determining when in the course of development they emerge. To be effective, such efforts must be appro priate to a youth's stage of development. A program that is effective in childhood may be ineffective in ' adolescence and vice versa. Moreover, the risk and protective factors targeted by violence prevention pro grams may be different from those targeted by inter vention programs, which are designed to prevent the reoccurrence of violence.
This report groups risk and protective factors into five domains: individual, family, peer group, school, and community, which includes both the neighborhood and the larger society (Box 4-1). Factors do not always fit neatly into these areas, however. Broken homes are classified as a family risk factor, but the presence of many such families in a community can contribute to social disorganiza tion, an important community-level risk factor (Bursik & Grasmick, 1993;.

# Risk Factors
Risk factors are not necessarily causes. Researchers identify risk factors for youth violence by tracking the development of children and adolescents over the first two decades of life and measuring how frequently par ticular personal characteristics and social conditions at a given age are linked to violence at later stages of the life course. Evidence for these characteristics and social conditions must go beyond simple empirical relationships, however. To be considered risk factors, they must have both a theoretical rationale and a demonstrated ability to predict violence-essential conditions for a causal relationship (Earls, 1994;Kraemer et al., 1997;. The reason risk factors are not considered causes is that, in most cases, scientists lack experimental evidence that changing a risk factor produces changes in the onset or rate of violence. As used in this report, risk factors are personal characteristics or environmental conditions that pre dict the onset, continuity, or escalation of violence.
The question of causality has practical implica tions for prevention efforts. Prevention depends large-erJ c copy available ly on risk factors being true causes of violence. In practical terms, research has amassed enough strong, consistent evidence for the risk factors discussed in this report to provide a basis for prevention programs, even though a strict cause-and-effect relationship has been established for relatively few of them.
Most of the risk factors identified do not appear to have a strong biological basis. Instead, it is theorized, they result from social learning or the combination of social learning and biological processes. This means that violent youths who have violent parents are far more likely to have modeled their behavior on their parents' behavior-to have learned violent behavior from them-than simply to have inherited it from them. Likewise, society's differing expectations of boys and girls-expecting boys to be more aggres sive, for example-can result in learned behaviors that increase or decrease the risk of violence.
The bulk of the research that has been done on risk factors identifies and measures their predictive value separately, without taking into account the influence of other risk factors. More important than any individual factor, however, is the accumulation of risk factors. Risk factors usually exist in clusters, not in isolation. Children who are abused or neglected, for example, tend to be in poor families with single par ents living in disadvantaged neighborhoods beset with violence, drug use, and crime. Studies of multiple risk factors have found that they have independent, addi tive effects-that is, the more risk factors a child is exposed to, the greater the likelihood that he or she will become violent. One study, for example, has found that a 10-year-old exposed to 6 or more risk fac tors is 10 times as likely to be violent by age 18 as a 10-year-old exposed to only one factor (Herrenkohl et al" 2000).
Researchers have theorized that risk factors also interact with each other, but to date they have found little evidence of interaction. What evidence does exist suggests that interactions between or among fac tors produce only small effects, but work in this area is continuing. To date, much more research has been done on risk factors than protective factors, but that picture, too, is changing.

# O

# ERIC

# Developmental Progression to Violence
Scientific theory and research take two different approaches to how youth violence develops-one that focuses on the onset of violent behavior and its frequency, patterns, and continuity over the life course and one that focuses on the emergence of risk factors at different stages of the life course. Chapter 3 describes two developmental trajectories for the onset of violent behavior-one in which vio lence begins in childhood (before puberty) and con tinues into adolescence, and one in which violence begins in adolescence.
In contrast, this chapter considers the timing of risk factors. It identifies the individual characteristics, experiences, and environmental conditions in child hood or adolescence that predict involvement in vio lent behavior in late adolescence-that is, age 15 to 18, the peak years of offending. Research shows that different risk factors may emerge in these two devel opmental periods and that the same risk factors may have different effect sizes, or predictive power, in these periods.
The timing of risk factors and the onset of vio lence are connected. Only risk factors that emerge in early childhood can logically account for violence that begins before puberty. However, these early risk factors may or may not be implicated in violence that begins in adolescence. In fact, studies show that many youths with late-onset violence did not encounter the childhood risk factors responsible for early-onset violence. For these youths, risk factors for violence emerged in adolescence Moffitt et al., 1996;Simons et al., 1994).

# Limitations of Risk Factors
Risk factors are powerful tools for identifying and locating populations and individuals with a high potential for becoming violent, and they provide valu able targets for programs aimed at preventing or reducing violence. But there are important limitations to our knowledge about and use of risk factors.
The following cautions are worth bearing in mind:
- No single risk factor or set of risk factors is power ful enough to predict with certainty that youths will become violent. Poor performance in school is a risk factor, for example, but by no means will all young people who perform poorly in school become violent. Similarly, many youths are exposed to mul tiple risks yet avoid becoming involved in violence (Garmezy, 1985;Rutter, 1985;Werner & Smith, 1982.
- Because public health research is based on observa tions and statistical probabilities in large popula tions, risk factors can be used to predict violence in groups with particular characteristics or environ mental conditions but not in individuals.
- Given these two limitations, assessments designed to target individual youths for intervention pro grams must be used with great care. Most individual youths identified by existing risk factors for vio lence, even youths facing accumulated risks, never become violent (Farrington, 1997;Lipsey & Derzon, 1998).
- Some risk factors are not amenable to change and therefore are not good targets for intervention (Earls, 1994;Hawkins et al., 1998a). Being bom male is an example.
- Of the risk factors that are amenable to change, some are not realistic targets of preventive efforts. Eliminating poverty is not a realistic short-term goal, for example, but programs that counter some of the effects of poverty are. (Eliminating or reduc ing poverty should be a high-priority long-term goal, however.)
- Some situations and conditions that influence the likelihood of violence or the form it takes may not be identified by longitudinal studies as risk factors (predictors) for violence. Situational factors such as bullying, taunting, and demeaning interactions can serve as catalysts for unplanned violence. The social context can influence the seriousness or form of violence-for example, the presence of a gun or a gathering crowd of peers that makes a youth feel he (or she) needs to protect his (or her) reputation. These may not be primary causes of violence, yet they are contributing factors and are important to understanding how a violent exchange unfolds. Such influences, although important, may not be identified in this report because of the way risk fac tors are defined.
- Many studies of risk factors, particularly earlier ones, drew their samples from white boys and young men. The limited focus of these studies calls into question their predictive power for girls and women and for other racial or ethnic groups.
Differences among cultures and their socialization and expectations of girls and boys may modify the influences of some risk factors in these groups.
Nonetheless, most of the risk factors identified in this report do apply broadly to all young people. All children go through the same basic stages of human development-and prevention of youth violence is based on understanding when and how risk factors come into play at various stages of development. Moreover, there is some evidence that most risk fac-79 tors are equally valid predictors of delinquency and violence regardless of sex, race, or ethnicity (Rosay et al., 2000;Williams et al., 1999). Sophisticated studies that identify how cultural differences affect the inter play of the individual and his or her surroundings will make possible more effective prevention efforts.

# Protective Factors
There is some disagreement about exactly what pro tective factors are. They have been viewed both as the absence of risk and as something conceptually distinct from risk (Guerra, 1998;lessor et al., 1995;Wasserman & Miller, 1998). The former view typically places risk and protective factors on the opposite ends of a continuum. For example, good par ent-child relations might be considered a protective factor because it is the opposite of poor parent-child relations, a known risk factor. But a simple linear rela tionship of this sort (where the risk of violence decreases as parent-child relations improve) blurs the distinction between risk and protection, making them essentially the same thing.1
The view that protection is conceptually distinct from risk (the view used in this report) defines protec tive factors as characteristics or conditions that inter act with risk factors to reduce their influence on vio lent behavior (Garmezy, 1985;Rutter, 1985;. For example, low family socio economic status is a risk factor for violence, and a warm, supportive relationship with a parent may be a protective factor. The warm relationship does not improve the child's economic status, but it does buffer the child from some of the adverse effects of poverty. Protective factors may or may not have a direct effect on violence (compare lessor et al., 1995 and.
Interest in protective factors emerged from research in the field of developmental psychopatholo gy. Investigators observed that children with exposure to multiple risk factors often escaped their impact. This led to a search for the characteristics or condi tions that might confer resilience-that is, factors that moderate or buffer the effects of risk (Davis, 1999;Garmezy, 1985;Rutter, 1987;Werner, 1989). Protective factors offer an explanation for why chil dren and adolescents who face the same degree of risk may be affected differently.
The concept of protective factors is familiar in public health. Wearing seat belts, for example, reduces the risk of serious injury or death in a car crash. Identifying and measuring the effects of protective factors is a new area of violence research, and infor mation about these factors is limited. Because they buffer the effect of risk factors, protective factors are an important tool in violence prevention.
Like risk factors, proposed protective factors are grouped into individual, family, school, peer group, and community categories. They may differ at various stages of development, they may interact, and they may exert cumulative effects (Catalano et al., 1998;Furstenberg et al., 1999;Garmezy, 1985;lessor et al., 1995;Rutter, 1979;Sameroff et al., 1993;. Just as risk factors do not necessarily cause an individual child or young person to become violent, protective factors do not guarantee that an individual child or young person will not become vio lent. They reduce the probability that groups of young people facing a risk factor or factors will become involved in violence.

# A Note on Sources
This chapter draws heavily on four important studies: Lipsey & Derzon's meta-analysis of 34 longitudinal studies on risk factors for violence (1998); Hawkins et al.'s study of malleable risk and protective factors drawn from 30 longitudinal studies, including some not included in the Lipsey & Derzon meta-analysis (Hawkins et al., 1998c); Paik and Comstock's meta analysis of 217 studies of exposure to media violence and its effects on aggression and violence (1994); and the National Institute of Mental Health's Taking Stock report (Hann & Borek, in press), an extensive review of research on risk factors for aggression and other behavior problems. . Additional risk factors and classes of risk factors have been added from other sources. For example, there is adequate evidence to establish harsh, lax, or inconsistent discipline as a separate risk factor, although Lipsey and Derzon include it in the poor par ent-child relations class. Academic failure, family con flict, and belonging to a gang are additional examples of risk factors not included in any of the meta-analyses.
The measure of effect size used in these tables is a bivariate correlation (r), or simple correlation between two variables. All estimates of effect size are statistically significant and are based on multiple stud ies, with those for risk classes typically involving more studies than those for separate risk factors. The studies reviewed in Lipsey and Derzon, Paik and Comstock, and Hawkins et al. are not cited here; how ever, other studies that were used to establish a risk factor or that are included in estimates of effect size are cited.3
There is a rich and extensive body of research on risks for antisocial behavior, externalizing behavior, conduct disorder, and aggression (Hann & Borek, in press). Each of these terms defines a pattern or set of behaviors that includes aggressive or violent behavior, but most of the behaviors included are either non physical, nonviolent acts or relatively minor forms of physical aggression. Risk factors for antisocial behav ior may be quite different from those that predict vio lent behavior (robbery, aggravated assault, rape, and homicide). Since antisocial behavior does not present the potential for serious injury or death that violence does, this report relies on studies that identify risk fac tors for serious offenses generally and violent behav ior specifically, bearing in mind that the vast majority of serious offenders report having been involved in violent offenses.

# Summary
Risk and protective factors can be found in every area of a child or adolescent's life, they exert different effects at different stages of development, and they gain strength in numbers. The public health approach to the problem of youth violence seeks to identify risk and protective factors, determine when in the life course they typically occur and how they operate, and enable researchers to design preventive programs to be put in place at just the right time to be most effective.
This chapter describes what is known about indi vidual, family, school, peer group, and community risk and protective factors that exert their effects in child hood and adolescence. It describes the power of early risk factors, which come into play before puberty, and late risk factors, which exert their influence after puberty, to predict the likelihood of youth violence.

# R is k Fa c t o r s in C h i l d h o o d
The first decade of life encompasses a vast period of human development. Infants form attachments to par ents or other loving adults and begin to become aware of themselves as separate beings. As toddlers, they begin to talk, to assert themselves, to explore the world around them, and to extend their emotional and social bonds to people other than their parents.
The start of school is a milestone in children's con tinuing social and intellectual development. Other chil dren become more important in their lives, though still not as important as family members. They begin to empathize with others and hone their sense of right and wrong. As they progress through elementary school, children gain valuable reasoning and problem-solving skills as well as social skills.
Exposure to or involvement in violence can disrupt normal development of both children and adolescents, with profound effects on their mental, physical, and emo tional health.4 In addition, exposure to violence affects children and adolescents differently at different stages of development (Marans & Adelman, 1997).
Young children exposed to violence may have nightmares or be afraid to go to sleep, fear being left alone, or regress to earlier behavior, such as baby talk or bed-wetting. They may exhibit excessive irritability or excitability. Violence in the family, especially, may inhibit young children's ability to form trusting rela tionships and develop independence.
Elementary school children who live in violent neighborhoods may also experience sleep distur bances and be less likely to explore their environ ment. In addition, they can become frightened, anx ious, depressed, and aggressive. They may have trou ble concentrating in school. Because they understand that violence is intentional, they may worry about what they could have done to prevent or stop it (Osofsky, 1999).
Violence also affects parents. Adults living in vio lent households or neighborhoods may not be able to keep their children safe or to protect them from harmful influences. Some parents living in unsafe neighbor hoods do not let their children play outside. While this solution may safeguard children temporarily, it can also impede healthy development. Parents in these situations understandably feel helpless and hopeless. Those who have been traumatized by violence themselves may, like their children, become anxious, withdrawn, or depressed. Under such circumstances, parents cannot respond spontaneously and joyously to their children, making it difficult for children to develop strong, secure attachments to their parents. Forming a bond with a lov ing, responsive parent or other adult caregiver is an essential factor in healthy development (Furstenberg et al., 1999;Osofsky, 1999;. Children and families exposed to or involved in violence may want to seek professional advice in addressing their mental, physical, and emotional health concerns.

# Risk Factors by Domain
A few risk factors for youth violence occur before birth. Others come into play as the child develops in response to his or her family and surroundings. Thus, most of the risk factors that exert an effect before puberty are found in the individual and family domains rather than in the larger world, a situation that changes dramatically in adolescence. Childhood risk factors are listed by domain in Box 4-1; effect sizes are listed in

# Individual
The most powerful early risk factors for violence at age 15 to 18 are involvement in general offenses and sub stance use before age 12. General offenses include seri ous, but not necessarily violent acts, such as burglary, grand theft, extortion, and conviction for a felony.
Children engaging in such crimes often come to the attention of the police and juvenile justice system. Numerous studies have documented the overlap between serious nonviolent and violent offenses in ado lescence, so early involvement in serious offenses car ries a substantial risk for violence later.
Experimentation with drugs, alcohol, tobacco, or some combination of these substances is not particu larly unusual by age 18, but use of these substances by children under the age of 12 is. Not only are these substances harmful to health, they are illegal. Thus, use of these substances signals antisocial attitudes and early involvement in a delinquent lifestyle that often comes to include violent behavior in adoles cence .
Two moderate risk factors emerge in childhood, being male and aggression. Boys (and young men) are far more likely than girls to be violent (see Chapter 2), yet some researchers have suggested that sex is a risk marker rather than a risk factor (Earls, 1994;Hawkins et al., 1998a;Kraemer et al., 1997). A risk marker is a characteristic or condition that is associated with known risk factors but exerts no causal influence of its own (Earls, 1994;.5 For example, many more boys than girls are hyperactive, a risk factor with a small effect size, so some of the predictive power of being male may actually be the influence of hyperactivity. Moreover, boys have tradi tionally been exposed to more violence than girls, and socially approved male role models are more aggres sive, suggesting that social learning plays a role in this risk factor. However, research indicates that being male confers risk even after accounting for other known risk factors. This suggests that being male is a risk factor rather than a risk marker, perhaps with some biological or biological-environmental interac tion as the causal mechanism.
Many studies have found aggression-character ized as aggressive and disruptive behavior, verbal aggression, and aggression toward objects-to be a moderate risk factor among boys, although there is some evidence that physical aggressiveness is actual ly responsible for most of the observed effect . Additional research is needed to sort out the unique influence of each of these types of aggression.
The remaining individual risk factors have rela tively small effect sizes. Various psychological condi tions, such as hyperactivity, impulsiveness, daring, and short attention span, pose a small risk for violence. A consistent individual predictor is hyperactivity/low attention, the central components of attentiondeficit/hyperactivity disorder (ADHD), a cognitive disorder that may be genetically influenced in some way (Hawkins et al., 1998a). ADHD is characterized by restlessness, excessive activity, and difficulty pay ing attention, traits that may also contribute to low aca demic performance, a risk factor in school. Hyperactivity is often found in combination with phys ical aggression, another risk factor. Some researchers question the independent effect of hyperactivity on later violence, suggesting that the effect is actually physical aggression (and perhaps low academic per formance) that was not controlled for in earlier studies of hyperactivity . There is little agreement about the mechanism linking hyperac tivity to violence.
The effects of children's exposure to television and film violence have been studied extensively in regard to aggression, but there is relatively little research regard ing the effects on more serious forms of violent behav ior (for an extended discussion, see Appendix 4-B). Experimental studies have found that exposure to media violence has a small average effect size (.13) on serious forms of violence ; the average effect size in cross-sectional survey studies was very small (.06). Two frequently cited longitudinal studies have examined the effects that exposure to tele vision violence in childhood produces on violent behavior during adolescence or early adulthood. One, in which participants reported having punched, beat en, or choked someone as young adults, found a signif icant predictive effect for women (.22) but no signifi cant effect for men (Huesmann et al., submitted). The other study, in which teenage males reported being involved in a knife fight, car theft, mugging, gang fight, or similar delinquent behavior, found a statistically sig nificant predictive effect in only one of nine tests . Exposure to violence appears to have a weak predictive effect on relatively immediate violence in experimental studies, but there is little con sistent evidence to date for a long-term predictive effect.
Little research has been done on violence in other media-video games, music videos, and the Internet. A recent meta-analysis by Anderson and Bushman (in press) reports that video game violence has a small average effect size (.19) on physical aggression in experim ental and cross-sectional studies. Theoretically, the influence of these interactive media might well be greater than that of television and films, which present a passive form of exposure, but there are no studies to date of the effects of exposure to these types of media violence and violent behavior. This is a different use o f the term "risk marker" than that proposed by Kraemer et al. (1997). They use risk marker to refer to a risk factor or cause (such as sex or race) that cannot, in practical terms, be changed by an intervention. This report focuses on its causal role rather than its am enability to change.
Problem behavior, another risk factor with a small effect size, refers to relatively minor problem behav iors such as stealing, truancy, disobedience, and tem per tantrums. While not serious in themselves, antiso cial behaviors may set the stage for more serious non violent or violent behavior later.
The medical or physical risk factor includes a number of conditions that as a group are somewhat predictive of violence. Prenatal and early postnatal complications, a more specific set of medical condi tions, have been found to have inconsistent effects across a number of studies (Hawkins et al., 1998c). These complications encompass a broad group of genetic conditions or physical injuries to the brain and nervous system that interfere with normal develop ment, including low birth weight, oxygen deprivation, and exposure to toxins such as lead, alcohol, or drugs (Hawkins et al., 1998b). Low resting heart rate, a con dition that has been studied primarily in boys, is asso ciated with fearlessness or stimulation seeking, both characteristics that may predispose them to aggression and violence (Raine et al., 1997;Hawkins et al., 1998c), but there is not enough evidence to establish this condition as a risk factor for violence. Some stud ies have even questioned its effects on aggression (Van HuIIe et al., 2000;Wadsworth, 1976;Kindlon et al., 1995). There is also no evidence that internalizing disorders-nervousness and withdrawal, anxiety, and worrying-are related to later violence (Hawkins et al., 1998c).
Low IQ, or low intelligence, includes learning problems and poor language ability. This risk factor has a small effect size and is often accompanied by other risk factors with small effect sizes, such as hyperactivity/Iow attention and poor performance in school.
Antisocial beliefs and attitudes, including dishon esty, rule-breaking, hostility to police, and a general ly favorable attitude toward violence, usually consti tute a risk factor in adolescence, not childhood (Hawkins et al., 1998c). Only dishonesty in child hood is predictive of later violence or delinquency, and its effect is small.

# O

# Family
There are no known strong risk factors for youth vio lence in the family domain, but low socioeconomic status/poverty and having antisocial parents are moderate factors. Socioeconomic status generally refers to par ents' education and occupation as well as their income.
Poorly educated parents may be unable to help their children with schoolwork, for example, and children living in poor neighborhoods generally have less access to recreational and cultural opportunities. In addition, many poor families live in violent neighborhoods, and exposure to violence can adversely affect both parents and children, as described above. Limited social and economic resources contribute to parental stress, child abuse and neglect, damaged parent-child relations, and family breakup-all risk factors with small effects in childhood.
Studies suggest that antisocial parents-that is, violent, criminal parents-represent an environmental rather than a genetic risk factor (Moffitt, 1987). In other words, children learn violent behavior by observ ing their parents rather than by inheriting a propensity for violence. In fact, attachment to parents, a possible protective factor, can have the opposite effect if the parents are violent (Hawkins et al., 1998c).
Among the early risk factors with small effect sizes on youth violence is poor parent-child relations. One specific risk factor in this class-harsh, lax, or inconsistent discipline-is also somewhat predictive of later violence (Hawkins et al., 1998c). Children need reasonable, consistent discipline to establish the boundaries of acceptable and unacceptable behavior. Children who are treated harshly may view rough treatment as acceptable, those who are given no guid ance may engage in whatever behavior gets them what they want, and children who receive mixed signals are completely at sea regarding appropriate behavior. Other family conditions, such as high stress, large size, and marital discord, also exert a small effect on later violence.
Another childhood predictor with a small effect size is broken homes, a category that includes divorced, separated, or never-married parents and a child's separation from parents before age 16. Separation from parents also operates as a distinct risk factor, again with a small effect size.
Abusive parenting in general and neglect in par ticular are predictors of later violence, but they have very small effect sizes. Neglect operates as a distinct risk factor, possibly because neglected children are less likely to be supervised or taught appropriate behavior. This is not to imply that child abuse and neglect do not cause serious problems in adolescence: Indeed, they have large effects on mental health prob lems, substance abuse, and poor school performance (Belsky & Vondra, 1987;Cicchetti & Toth, 1995;Dembo et al., 1992;Silverman et al., 1996;Smith & Thornberry, 1995). This finding is discussed in more detail below, in the section on unexpected findings and effects.

# School
The only early risk factor in the school domain is poor attitude toward and performance in school, and its effects are small. Numerous individual and family factors may contribute to poor performance, making it a fairly broad measure. For example, a child who is physically aggressive and is rejected by peers or who has difficulty concentrating or sitting still in class may understandably have difficulty performing aca demic tasks. Children who have been exposed to vio lence, as noted earlier, may also have trouble concen trating in school.

# Peer Group
Young children do not socialize extensively with other children and are not strongly influenced by peers. Peers become more important as children progress through elementary school, although school-age chil dren still look primarily to parents for cues on how to behave. Nonetheless, weak social ties to conventional peers and associating with antisocial peers both exert small effects in childhood.
Children with weak social ties are those who attend few social activities and have low popularity with conventional peers. School-age children often reject physically aggressive children because of their inappropriate behavior (Hann & Borek, in press;. The combination of rejection and aggressiveness exacerbates behavior problems, mak ing it more difficult for aggressive children to form positive relationships with other children. Indeed, recent research indicates that children who are both aggressive and rejected show poorer adjustment in elementary school than children who are aggressive, rejected, or neither (Hann & Borek, in press).
Being drawn to antisocial peers may introduce or reinforce antisocial attitudes and behavior in children. Indeed, aggressive children tend to seek each other out (Hann & Borek, in press).

# Community
Community risk factors, such as living in socially dis organized neighborhoods or neighborhoods with high rates of crime, violence, and drugs, are not powerful individual-level predictors in childhood because these external influences have less direct impact on children than on adolescents. They may well exert indirect influ ences through poor parenting practices, lack of family resources, and parent criminality or antisocial behavior.

# Summary
The most powerful early predictors of violence at age 15 to 18 are involvement in general offenses (serious, but not necessarily violent, criminal acts) and sub stance use. Moderate factors are being male, aggres siveness, low family socioeconomic status/poverty, and antisocial parents.

# R is k Fa c t o r s in A d o l e s c e n c e
Violence increases dramatically in the second decade of life, peaking during late adolescence at 12 to 20 percent of all young people and dropping off again sharply by the early twenties. Some of these youths followed the childhood-onset trajectory, becoming violent before puberty and escalating their rate of offending during adolescence. But over half of all vio lent youths begin their violent behavior in mid-to late adolescence. These youths gave little indication of problem behavior in childhood and did not have poor relations with their parents.
There are numerous theories about why violence begins in adolescence, but a few themes run through most of them Pepler & Slaby, 1994). Developmentally, puberty is accompanied by major physical and emotional changes that alter a young person's relationships and patterns of interac tion with others. The transition into adolescence begins the move toward independence from parents and the need to establish one's own values, personal and sexual identity, and the skills and competencies needed to compete in adult society. Independence requires young people to renegotiate family rules and degree of supervision by parents, a process that can generate conflict and withdrawal from parents. At the same time, social networks expand, and relationships with peers and adults in new social contexts equal or exceed in importance the relationships with parents. The criteria for success and acceptance among peers and adults change.
Adapting to all of these changes in relationships, social contexts, status, and performance criteria can generate great stress, feelings of rejection, and anger at perceived or real failure. Young people may be attracted to violent behavior as a way of asserting their independence of the adult world and its rules, as a way of gaining the attention and respect of peers, as a way of compensating for limited personal compe tencies, or as a response to restricted opportunities for success at school or in the community. Good rela tionships with parents during childhood will help in a successful transition to adolescence, but they do not guarantee it.
Adolescents exposed to violence at home may experience some of the same emotions and difficulties as younger school-age children-for example, fear, guilt, anxiety, depression, and trouble concentrating in school. In addition, adolescents may feel more vulner able to violence from peers at school or gangs in their neighborhood and hopeless about their lives and their odds of surviving to adulthood. These young people may not experience the growing feelings of compe tence that are important at their stage of development. Ultimately, their exposure to violence may lead them to become violent themselves. Studies have shown that O adolescents exposed to violence are more likely to engage in violent acts, often as preemptive strikes in the face of a perceived threat (Fagan & Wilkinson, 1998;Singer et al., 1994Singer et al., , 1995.

# Risk Factors by Domain
Not surprisingly, different risk factors for violence assume importance in adolescence. Family factors lose predictive value relative to peer-oriented risk fac tors such as weak social ties to conventional peers, antisocial or delinquent friends, and membership in a gang (Table 4-1). Even involvement in general offenses, which had the largest effect size in child hood, has only a moderate effect size in adolescence.

# Individual
In early adolescence, involvement in general offens es-that is, illegal but not necessarily violent acts, including felonies-becomes a moderate risk factor for violence between the ages of 15 and 18. Its pre dictive power lessens from childhood, largely because teenagers are somewhat more likely than children to engage in illegal behavior.
. Psychological conditions, notably , restlessness, difficulty concentrating, and risk taking,, have small effect sizes in adolescence. Restlessness and difficul ty .concentrating can affect performance in school, a risk factor whose importance increases slightly in ado lescence. Risk taking gains predictive power in early adolescence, particularly in combination with other factors. A reckless youth who sees violence as an acceptable means of expression, for example, is more likely to engage in violent behavior.
Aggressiveness exerts a small effect on later vio lence among adolescent males, as does simply being male. While aggressiveness is unusual in children between the ages of about 6 and 10, it is not terribly unusual in adolescence. Similarly, physical violence and crimes against persons in early adolescence have a small effect on the likelihood of violence at ages 15 to 18.
Antisocial attitudes and beliefs, including hostility toward police and a positive attitude toward violence, are more important predictors among adolescent boys than they are among children, but their effect sizes remain small. Antisocial behavior and low IQ continue to have small effect sizes in adolescence.
Substance use, which was a strong predictor of later violence for children, poses a small risk of later violence for adolescents. The question as to whether drug use causes young people to become violent is complex and has been widely studied (see Miczek et al., 1994 for a review), but there is little compelling pharmacological evidence linking illicit drug use and violence. In one large study, youths reported that over 80 percent of the violent incidents they initiated had not been preceded by drug use, including alcohol use . Thus, the risk may lie more in the characteristics of the social settings in which drug use and violence are likely to occur than in any effect of drugs on behavior (Parker & Auerhahn, 1998;.
The majority of violent adolescent offenders use alcohol and illicit drugs (see Chapter 3). Illicit drug use tends to begin after the onset of violence and to be associated with more frequent violent behavior and a longer criminal career . This find ing suggests that drug use may contribute to continued violence rather than to the onset of violence, but it is far from conclusive. Evidence shows that some vio lent behavior stems from robberies or other attempts to.get money to support a drug habit but also that this link is relatively rare. If any substance can be said to cause youth violence, that substance is alcohol (APA, 1993;Parker & Auerhahn, 1998); however, this causal link is inconclusive because adolescent drinking is dependent to a large degree on the situation and social context in which it takes place (for reviews, see Parker & Auerhahn, 1998;Pemanen, 1991;Roizen, 1993).

# Family
Parents' direct influence on behavior is largely eclipsed by peer influence during adolescence. Not surprisingly, therefore, most family risk factors dimin ish in importance, including the influence of antisocial parents and low socioeconomic status, the most pow erful early risk factors. There are no large or even mod erate risk factors in the family domain in adolescence.
Poor parent-child relations continue to have a small effect size, but for adolescents this category includes inadequate supervision and monitoring of young people's activities and low parental involve ment, in addition to inappropriate discipline (Elliott et al., 1985;Hawkins et al., 1998a;Roitberg & Menard, 1995). Broken homes and parental abuse also exert small effects. Other adverse family conditions present a risk factor; for example, some studies have found that family conflict is a risk factor for violence among adolescent males.
Although parents can and do influence their ado lescents' behavior, they do so largely indirectly. The kind of peers chosen by young people, for example, is related to the relationship they have with their parents Hill et al., 1999;Simons et al., 1994).

# School
There are no large or moderate risk factors for vio lence in the school domain, but poor attitude toward or performance in school-particularly if it leads to academic failure-is a slightly larger risk factor in early adolescence than in childhood.
Research on school violence indicates that a cul ture of violence has arisen in some schools, adversely affecting not just students but teachers and adminis trators as well (Gottfredson et al., in press;Lorion, 1998). Students exposed to violence at school may react by staying home to avoid the threat or by taking weapons to school in order to defend themselves . For their part, teachers may bum out after years of dealing with discipline problems and threats of violence.
Schools located in socially disorganized neighbor hoods are more likely to have a high rate of violence than schools in other neighborhoods (Laub & Lauritsen, 1998). At the same time, however, researchers emphasize that most of the violence to which young people are exposed takes place in their home neighborhood or the neighborhood surrounding the school, not in the school itself (Laub & Lauritsen, 1998). Individual schools, like individual students, do not necessarily reflect the characteristics of the sur rounding neighborhood. A stable, well-administered school in a violent neighborhood may function as a safe haven for students. Some gang activity takes place in schools, but school gangs are generally younger and less violent than street gangs, which form in neighborhoods (Laub & Lauritsen, 1998). Gangs in schools increased dra matically (by 87 percent) between 1989 and 1995 but have recently declined (see Chapter 3). The chances of becoming a victim of violence are more than two and one-half times as great in schools where gangs are reported, and these schools are disproportionately located in disadvantaged, disorganized neighborhoods (Met Life, 1993;.
Peer groups complicate the picture further. They operate both in neighborhoods and in schools, but the concentration of young people in schools may intensi fy the influence of these groups. One large study of adolescent males found that some schools have domi nant peer groups that value academic achievement and disapprove of violence, while others have groups that approve of the use of violence (Felson et al., 1994). This study found that the risk of becoming involved in violence varied depending on the dominant peer cul ture in their school, regardless of their own views about the use of violence.

# Peer Group
Peer groups are all-im portant in adolescence. Adolescents who have weak social ties-that is, who are not involved in conventional social activities and are unpopular at school-are at high risk of becoming violent, as are adolescents with antisocial, delinquent peers. These two types of peer relationships often go together, since adolescents who are rejected by or unpopular with conventional peers may find accept ance only in antisocial or delinquent peer groups. Social isolation-having neither conventional nor antisocial friends-is not a risk factor for violence, however (Cairns & Cairns, 1991;Fergusson & Lynskey, 1996;. A third risk factor with a large effect size on violence is belonging to a gang. Gang mem bership increases the risk of violence above and O beyond the risk posed by having delinquent peers (Thornberry, 1998). These three peer group factors appear to have independent effects, they sometimes cluster together, and they are all powerful late predic tors of violence in adolescence.
Researchers who have studied what causes young people to join gangs have found that the risk factors for gang membership are virtually the same as those for violence generally (Hill et al., 1999). The notion that gangs act as surrogate families for children who do not have close ties to their own fam ilies is not borne out by recent data (Hill et al., 1999), but gangs do strengthen young people's sense of belonging, their independence from parents, and their self-esteem. Estimates from law enforcement agencies indicate that gang members are overwhelm ingly male and the great majority (almost 80 percent) are African American or Hispanic . But surveys in which young peo ple identify themselves as gang members suggest that there are substantially larger proportions of white and female gang members. In a survey of near ly 6,000 8th graders in 1995, 25 percent of white stu dents and 38 percent of female students reported they were gang members (Esbensen & Osgood, 1997). Lacking comparisons within ethnic groups, it is difficult to tell whether ethnicity per se is a risk factor in gang membership.

# Community
Increasing involvement in the community is a healthy part of adolescent development, unless the communi ty itself poses a threat to health and safety. Social dis organization and the presence of crime and drugs in the neighborhood pose a small risk of violence when measured on an individual level, as they are in Table 4-1. As noted in the table, however, both of these risk factors have a substantially greater effect on the neighborhood level, where they measure the average rate of violent offending by youths living in the neigh borhood or community.
Socially disorganized communities are character ized in part by economic and social flux, high turnover of residents, and a large proportion of disrupted or sin-gle-parent families, all of which lessen the likelihood that adults will be involved in informal networks of social control. As a result, there is generally little adult knowledge or supervision of the activities of teenagers and a high rate of crime. Moreover, in areas experienc ing economic decline, there are likely to be few neigh borhood businesses. In such an environment, it is hard for young people to avoid being drawn into violence. Not only are they on their own after school, they are exposed to violent adults and youth gangs, they have few part-time job opportunities, and their neighborhood is not likely to offer many after-school activities such as sports or youth groups (Bursik & Grasmick, 1993;Sampson et al., 1987).
Social disorganization is also a risk factor for vio lence in rural areas. One study of rural communities found that poverty plays a less important role in pre dicting violence than residential instability, broken homes, and other indicators of social disorganization (Osgood & Chambers, 2000). In fact, very poor areas were not characterized by high residential instability or a large proportion of broken homes. In cities, how ever, the combination of poverty with instability and family disruption is predictive of violence (Bursik & Grasmick, 1993;.
Adolescents who are exposed to violence in their neighborhood feel vulnerable and unable to control their lives. These feelings can lead to helplessness and hopelessness. Such young people may turn to violence as a way of asserting control over their surroundings. They may arm themselves or even join a gang for pro tection. Studies have shown that adolescents exposed to violence are more likely to engage in violent acts, often as preemptive strikes in the face of a perceived threat (Singer et al., 1994(Singer et al., , 1995.
Neighborhood adults who are involved in crime pose a risk because young people may emulate them. Easily available drugs add to the risk of violence. As noted earlier, drug use is associated with both a higher rate of offending and a longer criminal career . More important, ready availability of drugs indicates that considerable drug trafficking is taking place in the neighborhood-and drug trafficking is dan gerous for buyer and seller alike.

# Summary
Violence peaks during the second decade of life. The youths who first became violent in childhood escalate their violence in adolescence, and a larger group of young people embarks on violence in adolescence. For some young people, violence represents a way of gain ing the respect of peers, enhancing their sense of self worth, or declaring their independence from adults. Violence drops off as adolescents enter adulthood and assume adult roles.
Parents' direct influence on behavior is largely sup planted in adolescence by peer influences. Thus the most powerful peer predictors of violence in adoles cence are weak social ties to conventional peers, ties to antisocial, delinquent peers, and belonging to a gang.

# Unexpected Findings and Effects
This chapter does not identify a number of characteris tics and conditions frequently thought of as risk factors. Furthermore, some of the risk factors that have been identified may exhibit smaller effect sizes than expect ed. There are two reasons for this. First, this report relies on longitudinal studies, which identify risk fac tors and their effect sizes on the basis of their ability to predict future behavior. Much of this research involves identifying risks for aggression, externalizing behavior, or antisocial behavior-not risks for violence. While there is considerable overlap between the risk factors for aggression and those for violence, there are some important differences, particularly with respect to effect sizes (Hann & Borek, in press). Television violence, for example, has a very large effect on aggressive behavior but only a small effect on violence. Second, some stud ies that have been widely cited in the media involve cross-sectional and retrospective research designs, which are inappropriate for identifying factors that pre dict future violence.
Conduct disorder has been linked to youth vio lence in numerous studies, but the cluster of symp toms used to determine this disorder includes physi cal aggressiveness, nonphysical aggressiveness, and antisocial attitudes and beliefs. For purposes of pre dicting violence, the critical question is: What com ponents of this disorder actually confer risk? There is some evidence that physical aggression accounts for most of the predictive power of conduct disorder  and has a moderate to small effect size as a predictor of violence. Antisocial attitudes and beliefs also predict violence, but with an even smaller effect size. The three com ponents of conduct disorder generally cluster togeth er, which accounts for their having been combined into a single risk factor in earlier studies. Other childhood disorders such as attention-deficit/hyperactivity disorder, depressive and anxiety disorders, and their symptoms do not cause violent behavior, but their presence often signals serious behavioral and emotional problems that negatively affect fami ly, social, and academic functioning, domains of risk for violent behavior.
Race has long been considered a risk factor for the onset of violence, and it is included as a risk fac tor in most studies using simple bivariate predictors of violence. The question is whether race predicts violence once other known risk factors are taken into account. Studies that have accounted for the effects of other known risk factors have typically found no significant effect of race on youth violence Roitberg & Menard, 1995). Thus, race appears to be a risk marker rather than a risk factor. Race is a proxy for other known risk factors-living in poor, single-parent families, doing poorly at school, and being exposed to neigh borhood disadvantage, gangs, violence, and crime. The evidence suggests that the link between race and violence is based largely on social and political dis tinctions rather than biological differences.
Ethnicity has also been proposed as a risk factor, but it has not been studied extensively enough to include here. Young people from ethnic minorities may be subject to prejudice and thus to limited opportunity, and they may face unique stresses when their family culture conflicts with the dominant U.S. culture. At the same time, their ethnic culture may offer them strong support and guidance and thus function as a protective factor (APA, 1993).
Child abuse is widely considered to be a powerful risk factor for youth violence. This belief is based on a number of early studies that suffered from serious methodological problems (see Dodge et al., 1990;Garbarino & Plantz, 1986;Howing et al., 1990;and Widom, 1989 for reviews). In more sophisticated, con trolled longitudinal studies, the effects are much small er (see Table 4-1), a finding that holds for both self report and official record studies. In addition, studies reporting on child abuse as a predictor of nonviolent delinquent behavior or less serious offenses find larger effect sizes than those cited here for violence or serious delinquency (Bolton et al., 1977;Widom, 1989Widom, ,1991Zingraff et al., 1993Zingraff et al., , 1994. Neither sexual abuse nor physical abuse is a significant predictor of youth violence when considered alone (Hawkins et al., 1998c). Sexual abuse has been linked to criminal behavior in adulthood (Widom & Ames, 1994), but not to violence in adolescence.
Although the effect size of child abuse or neglect is small when a correlation measure is used (as in Table 4-1), the relative risk of violence among abused or neglected children can be substantial. Knowing that a child was abused does not help much in predicting future violence, however, since the vast majority of abused children do not become violent. For example, one longitudinal study showed that 5 percent of abused children were arrested for a violent crime by age 18, compared to 3 percent of nonabused children (Widom, 1991). The relative risk of arrest for violence is nearly twice as great in the abused group as in the nonabused group, yet the correlation for this relation ship is .07, a small effect size.6 In other words, even though the probability of later violence is substantial ly higher among abused than nonabused youths in this study, the correlation is small because the majority of all youths (95 percent of abused and 97 percent of nonabused youths) did not become violent.
When the proportion of youths who become vio lent is greater, the relative risks appear to be lower. Thus, when subjects in the 1991 Widom study were tracked to age 30, the relative risk of violence dropped to 1.3 (Widom, 2000). In the one longitudi nal self-report study to date, which had relatively high proportions of abused children reporting vio lence, the relative risk of violence was 1.2 (Smith & Thornberry, 1995). In both of these cases, the corre lation was less than .10.
Heredity does not seem to play a strong role in vio lence (see Cary, 1994 for a review). While there is some evidence supporting a genetic effect, the proposed mechanisms are very complex and nonspecific (Turbin, 2000). Neurotransmitters such as dopamine, serotonin, and GABA may play a role in aggression, but so far their mechanisms of action are unclear and there is insufficient evidence to consider them predictors of violence. In general, there are no known neurobiologi cal patterns that are precise and specific enough to be considered reliable risk factors for violent behavior .
Drug trafficking in early adolescence predicts later violence (Hawkins et al., 1998c;Herrenkohl et al., 2000;Menard et al., in press;. This risk factor is not included here because only one study presents corre lations (or the data necessary to calculate them); there fore, average effect size could not be estimated. In the Menard et al. study, the correlation between selling marijuana and violence in adolescence was .33; for selling hard drugs, it was .27. In the Hawkins et al. study, the odds ratio for selling drugs at age 14 and violence at age 18 was 3.34; it was 4.55 for selling at age 16 and violence at age 18. Drug selling'thus appears to have at least a moderate effect size.

# Pr o p o s e d Protective Factors in C h il d h o o d a n d A do lescence
Research on resilience and the public health approach to the problem of youth violence have brought a new awareness of, and research on, pro tective factors-those aspects of the individual and his or her environment that buffer or moderate the effect of risk. Identifying and understanding how protective factors operate is potentially as important to violence prevention and intervention efforts as research on risk factors.
To date, the evidence regarding protective factors against violence has not met the standards established for risk factors. Therefore, this report does not refer to protective factors, only to proposed protective factors (Table 4-2). There are several reasons for this: Not all studies define protective factors as buffering the effects of risk; most studies have looked for an effect on antisocial behavior in general, not on violence specifically; and those that have found buffering effects on violence have not been adequate ly replicated. This does not mean that protective fac tors do not exist, just that more research is needed to identify them.7
Most studies of protective factors do not specify when in the course of development these factors exert their buffering effects or how they change over the life course. Further study is needed to clarify these points; therefore, Table 4-2 does not show age of onset for the proposed protective factors listed.

# A Note on Sources
The authors of a 1995 longitudinal study on protective factors and their buffering effects on the risk of prob lem behavior in adolescence (lessor et al., 1995) recently reexamined their data to see whether they could find any buffering effect specifically on vio lence. They did find a buffering effect, but their results must be considered preliminary until they are replicat ed by others. Nonetheless, these findings are encour aging, since they indicate that several of the factors identified as protective against problem behavior also provided a buffering effect against violence. By implication, other studies that have demonstrated buffering effects on the risk of antisocial behavior or general delinquency (for example, Fergusson & Lynskey, 1996) may also contain evidence of potential protective factors against violence. The discussion of proposed protective factors in this report rests on the 7 There is a fairly extensive body o f research on protective factors in the field o f psychopathology (Carmezy, 1985;Rae-Crant et al., 1989;Rolf et al., 1993;Rutter, 1979Rutter, , 1985Rutter et al., 1979;Stattin et al., 1997;W erner andSmith, 1982, 1992). There are also a number o f studies focusing on delinquency that purport to identify protective factors (Brewer et al., 1995  reanalysis of the 1995 study data (Turbin, 2000), as well as on results from other studies, bearing in mind the caveats noted above. The 1995 lessor study grouped possible protective factors together and found that students who scored high on this index of protection were buffered from the effects of risk, compared to students who scored low on the index. The index was composed of seven psy chosocial protective factors: attitudinal intolerance of deviance, positive orientation to health, religiosity,, positive relations with adults, perceived consequences for misbehavior, friends as models for conventional behaviors, and high involvement in conventional activ ities. In an analysis of specific factors, however, only two-an intolerant attitude toward deviance and com mitment to school-had significant protective effects. The new findings show that the same two factors appear to exert a significant, though small, buffering effect on risk factors for violence.

# Proposed Protective Factors by Domain
One of the proposed protective factors shown to have a buffering effect on the risk of violence is an individ ual characteristic, and the other falls into the domain BEST COPY AVAILABLE of school; both are classed as having a small effect. No other factors in the individual, family, school, or peer group domains have been shown to exert signifi cant buffering effects on risk factors for violence, although they have been shown to moderate the risk of antisocial behavior or delinquency. No protective fac tors have been proposed yet in the community domain.

# Individual
An intolerant attitude toward deviance, including vio lent behavior, is the strongest proposed protective fac tor. It reflects a commitment to traditional values and norms as well as disapproval of activities that violate these norms. Young people whose attitudes are anti thetical to violence are unlikely to become involved in activities that could lead to violence or to associate with peers who are delinquent or violent.
The four remaining individual factors have not yet been shown to moderate violence, although they may buffer risks for antisocial behavior or general delin quency. High IQ has been cited as a possible protec tive factor (Fergusson & Lynskey, 1996;Garmezy, 1985;Rutter, 1985;Werner & Smith, 1982). Children with above-average IQs may exhibit qualities, such as curiosity and creativity, that help them make the most of early educational, artistic, and cultural experiences. Above-average IQ can also help a child excel in school. High IQ may increase an adolescent's chances of benefiting from educational, creative, and cultural opportunities. For youths facing multiple risk factors, exposure to the wider world may open a window on alternative values and lifestyles.
Being bom female has also been cited (Garmezy, 1985;Rutter, 1985;Wemer & Smith, 1982), but it is the opposite of being bom male, a risk factor, and as yet there is no evidence of a buffering effect. Being a girl entails less exposure to violence, less impulsive ness and daring, and being expected to behave less aggressively than boys.
Some studies have proposed positive social ori entation as a protective factor (Garmezy, 1985;lessor et al., 1998;Rutter, 1985;Werner & Smith, 1982). Like commitment to school, a positive social orientation indicates that a young person has adopt ed traditional values and norms, a slightly different emphasis than intolerance of deviance. This pro posed factor appears to be the opposite of antisocial attitudes and beliefs, a late-onset risk factor that has a small effect size.
Perceived sanctions for transgressions, a protec tive factor in the earlier lessor study (1995), refers to perceived peer disapproval of deviant behavior. The reanalysis of those original data reveals that this pro posed factor has no significant protective effect on risk of violence or problem behavior.

# Family
There is no doubt that an essential aspect of healthy child development is forming a secure attachment in infancy to a parent or other adult who senses and responds to a baby's needs (Bell & Fink, 2000). Likewise, researchers agree that having a loving adult who is interested in and supportive of a child or young person's ideas and activities helps that child or ado lescent develop the confidence and competence need ed to progress from one stage of development to the next. Good relations with an adult who supports con ventional behavior and disapproves of delinquent O behavior can provide invaluable guidance for young people. The question is whether these relationships moderate the effects of exposure to risk and thus fit the definition of a protective factor.
A warm, supportive relationship with parents or other adults has been shown to protect against antiso cial behavior, but studies so far have not found a sig nificant buffering effect on the risk of violence (Hawkins et al., 1998c;Klein & Forehand, 2000;Rutter, 1979;Turbin, 2000;Wemer & Smith, 1992).
It is uncertain whether family protective factors, like family risk factors, become less influential as young people progress through adolescence. Parental support and encouragement remain important, but even parents who have had a good relationship with thenchildren before puberty may affect their adolescents' behavior only indirectly-for example, through choice of friends . This indirect influence is not inconsequential, however; associating with peers who disapprove of violence may inhibit later violence in young people (Hawkins et al., 1998c), and parents' positive evaluation of peers has been found to reduce the risk of delinquency .
Several studies have pointed to monitoring or supervision of activities as a protective factor against delinquency and antisocial behavior, but this is essen tially the opposite of failure to monitor, an adolescentonset risk factor with a small effect size. To date, no evidence of moderating effects on the risk of violence has been presented (Baldwin et al., 1990;Klein & Forehand, 2000;.

# School
Commitment to school is the second proposed protec tive factor that has been found to buffer the risk of youth violence. Young people who are committed to school have embraced the goals and values of an influential social institution. Such young people are unlikely to engage in violence, both because it is incompatible with their orientation and because it would jeopardize their achievement in school and their standing with adults (lessor et al., 1995;Turbin, 2000). This proposed factor is included because it appears to buffer the risk of violence, not because it is 93 the opposite of poor attitude toward or performance in school, a risk factor with small effect sizes in both childhood and adolescence.
School can give adolescents who face multiple risk factors a place in which to excel socially and academi cally. Achievement in school and the approval of teach ers provide the recognition so important to adolescent development-recognition some adolescents do not receive from other sources. Encouragement from teachers can give young people the confidence to seek continued educational or job skills training. In addition, schools with peer groups that value academic achieve ment may lower students' risk of becoming involved in violence (Felson et al., 1994). Unfortunately, schools with a culture of violence may be unable to exert their very important protective function.
Extracurricular activities in art, music, drama, school publications, and the like give adolescents an opportunity to participate in constructive group activities and achieve recognition for their efforts. Studies have found that recognition for or involve ment in conventional activities-whether family, school, extracurricular, religious, or community-is a protective factor against antisocial behavior (lessor et al., 1995;Rae-Grant et al., 1989). The reanalysis of the lessor data shows that involvement in family, volunteer, and school club activities other than sports has an insignificant effect on risk for violence (Turbin, 2000).

# Peer Group
Having friends who behave conventionally is a pro posed protective factor that seems to reduce the risk of delinquency, but there is no evidence of a true buffer ing effect on specific risk factors. Buffering effects on violence were not significant in the reanalysis of the lessor data (Turbin, 2000; see also . However, as noted earlier, researchers have found that associating with peers who disapprove of violence may inhibit violence in young people (Hawkins et al., 1998c;lessor et al., 1995).

# O

# Summary
Although the body of research on protective factors is growing, very little work has been done specifically on protective factors that buffer the risk of violence. Some researchers have identified individual and environmen tal characteristics that can be considered candidates for protective factors. Lacking adequate scientific evidence of the nature, mechanism, size, and timing of these can didates' moderating effects, however, this report con siders all of them proposed protective factors.
One recent reanalysis of earlier data has found two proposed protective factors that seem to buffer the risk of violence-an intolerant attitude toward deviance and commitment to school. These two fac tors appear to exert a statistically significant, though small, buffering effect on the risk of violence, but until these findings are replicated, they must be considered preliminary.
Identifying and understanding how protective fac tors operate is as important to preventing and stopping violence as identifying and understanding risk factors. This area of the public health approach to youth vio lence cries out for more research.

# C o n c l u s io n s
Scientists have identified a number of personal char acteristics and environmental conditions that put chil dren and adolescents at risk of violent behavior and some that seem to protect them from the effects of risk. These risk and protective factors can be found in every area of life, they exert different effects at differ ent stages of development, they tend to appear in clus ters, and they appear to gain strength in numbers. The public health approach to youth violence involves identifying risk and protective factors, determining when in the life course they typically come into play, designing preventive programs that can be put in place at just the right time to be most effective, and making the public aware of these findings.
Many years of research have yielded valuable insights into the risk factors involved in the onset and developmental course of violence. Less work has been done on protective factors, but that situation is changing. Some basic principles have emerged from these studies:
Risk and protective factors exist in every area of life-individual, family, school, peer group, and community. Individual characteristics interact in complex ways with a child's or adolescent's envi ronment to produce violent behavior.
Risk and protective factors vary in predictive power depending on when in the course of human devel opment they occur. As children move from infancy to early adulthood, some risk factors will become more important and others less important. Substance use, for example, is a far more powerful risk factor at age 9 than it is at age 14.
Risk factors do not operate in isolation-the more risk factors a child or young person is exposed to, the greater the likelihood that he or she will become violent. Risk factors can be buffered by protective factors, however. An adolescent with an intolerant attitude toward violence is unlikely to engage in violence, even if he or she is associating with delin quent peers, a major risk factor for violence at that age.
Risk factors increase the likelihood that a young person will become violent, but they may not actu ally cause a young person to become violent. Scientists view them as reliable predictors or even as probable causes of youth violence. They are use ful for identifying vulnerable populations that may be amenable to intervention efforts. Risk markers such as race or ethnicity are frequent ly confused with risk factors; risk markers have no causal relation to violence.
No single risk factor or combination of factors can predict violence with unerring accuracy. Few young people exposed to a single risk factor will become involved in violent behavior; similarly, most young people exposed to multiple risks will not become violent. By the same token, protective factors cannot guarantee that a child exposed to risk will not become violent.
Researchers have identified at least two onset tra jectories for youth violence: a childhood trajectory that begins before puberty and an adolescent one that begins after puberty. Violence peaks during the second decade of life. The small group of offenders who began their violent behavior in childhood commits more violent offenses, and the larger group of adolescent offenders begins to become involved in violence.
- Early risk factors for violence in adolescence include involvement in serious (but not necessari ly violent) criminal acts and substance use before puberty, being male, aggressiveness, low family socioeconomic status/poverty, and antisocial par ents. All of these early risks stem from a child's individual characteristics and interaction with his or her family. The influence of family is largely supplanted in adolescence by peer influences; thus, risk factors with the largest predictive effects in adolescence include weak social ties to conven tional peers, ties to antisocial or delinquent peers, and belonging to a gang. Committing serious (but not necessarily violent) criminal offenses is also an important risk factor in adolescence. Drug selling is a risk factor, but its effect size has not been established.
- Identifying and understanding how protective fac tors operate is potentially as important to preventing and stopping violence as identifying and under standing risk factors. Several protective factors have been proposed, but to date only two have been found to buffer the risk of violence-an intolerant attitude toward deviance and commitment to school. Protective factors warrant more research attention.
Violence prevention and intervention efforts hinge on identifying risk and protective factors and determining when in the course of development they emerge. More research in these areas is needed, par ticularly concerning why violence stops or continues in childhood and adolescence.-Nonetheless, the research carried out to date provides a solid founda tion for programs aimed at reducing risk factors and promoting protective ones-and thereby preventing violence, the subject of Chapter 5.

# R e f e r e n c e s
A m erican Psychological A ssociation. (1993).
Violence  1972). During this period, new media emerged-video games, cable television, music videos, and the Internet. As they gained popularity, these media, along with tele vision, prompted public concern and research attention.
Recent surveys depict the abundance of (primari ly electronic) media in U.S. homes (Roberts et al., 1999;Woodard, 1998) and the extensive presence of violence within the media landscape (Wilson et al., 1997(Wilson et al., , 1998. They also show that the proliferation of new media has expanded the opportunities for chil dren to be exposed to media violence at home. Current psychological theory suggests that the interactive nature of many of these new media may affect chil dren's behavior more powerfully than passive media such as television. Research to test this assumption is not yet well developed, and accurate measurement is needed to determine how much violence children are actually exposed to through various media-and how patterns of exposure vary among American youths.
In reading this discussion of research on the impact of media violence on America's youth, a few major points should be kept in mind:
- First, research on the effects of media violence examines many kinds of outcomes in young people.
Researchers have focused primarily on aggression, an outcome that psychologists define as any behav ior, physical or verbal, that is intended to harm another person. Physical aggression may range from less serious acts, such as pushing or shoving, to more serious physical contact and fighting, to very serious violent acts that carry a significant risk of injury or death, such as assault, robbery, rape, and homicide. Some studies have focused on how media violence affects aggressive thinking, including beliefs and attitudes. Other studies have focused on the effects of media violence on aggressive emotions-that is, on emotional reactions, such as anger, that are relat ed to aggressive behavior. In this discussion, the label "violence" is reserved for the most extreme end of the physical aggression spectrum.
- Second, as noted in Chapter 4, the preponderance of evidence indicates that violent behavior seldom results from a single cause; rather, multiple factors converging over time contribute to such behavior. Accordingly, the influence of the mass media, how ever strong or weak, is best viewed as one of the many potential factors that help to shape behavior, including violent behavior.
- Third, a developmental perspective is essential for understanding how media violence affects youth behavior and for framing any coherent public health response to it. Although this report focuses general ly on the violent behavior of adolescents, it is criti cal to understand how children are influenced by and respond to media violence, especially in order to recognize and help those who are particularly susceptible to adverse effects. Most youths who are aggressive and engage in some forms of antisocial behavior do not become violent teens and adults. However, it is well established that many violent adolescents and adults were highly aggressive and 1 0 4 8;
even violent at younger ages, and the highly aggres sive child is at increased risk of growing up to be a more aggressive young adult . Because influences that promote aggressive behavior in some young children can contribute to increasingly aggressive and even violent behavior many years later, it is important to understand the early factors that may play a role in later outcomes.
- Fourth, a growing body of research supports theo ries that explain how exposure to media violence would activate aggressive behaviors or attitudes in some children. Humans begin imitating other indi viduals at a very early age, and young children learn many motor and social skills by observing the behavior of others (Bandura, 1977). Social interac tions shape the scripts for behavior that children acquire, but observational learning is a powerful mechanism for acquiring social scripts throughout childhood (Huesmann, 1998). Most researchers agree that such observational learning is probably the major psychological process underlying the effects of media violence on aggressive behavior. This same process could explain how prosocial behavior depicted in the media might encourage positive behavior in children (Friedlander, 1993;Harold, 1986;Mares, 1996).

# M e d ia V io l e n c e : Ex p o s u r e a n d C o n t e n t
American children and youths spend, on average, more than 4 hours a day with television, computers, videotaped movies, and video games (Roberts et al., 1999;Woodard, 2000). But their exposure to media varies considerably, depending on their age, parental viewing habits, and family socioeconomic status (SES). Most systematic research on children's expo sure to violent media dates back to the 1970s, when most families did not have access to cable television, music videos, video games, or the Internet. As noted earlier, very few contemporary studies systematically document children's actual consumption of violent media; this is particularly true for the newer media. Several content analyses over the last 30 years have systematically examined violence on television (Gerbner et al., 1980;Potter et al., 1995;Signorielli, 1990). The largest and most recent of these was the National Television Violence Survey (NTVS)1 (Wilson et al., 1997(Wilson et al., , 1998, which examined the amount and content of violence2 on American televi sion for three consecutive years, as well as contextual variables that may make it more likely for aggression and violence to be accepted, learned, and imitated. Smith and Donnerstein (1998) report the following NTVS findings:
- 61 percent of television programs contain some vio lence, and only 4 percent of television programs with violent content feature an "antiviolence" theme.
- 44 percent of the violent interactions on television involve perpetrators who have some attractive qual ities worthy of emulation.
- 43 percent of violent scenes involve humor either directed at the violence or used by characters involved with violence.
- Nearly 75 percent of violent scenes on television feature no immediate punishment for or condemna tion of violence.
- 40 percent of programs feature "bad" characters who are never or rarely punished for their aggres sive actions.
The NTVS report notes that many television pro grams fail to depict the harmful consequences of vio lence. Specifically, it finds that of all violent behav ioral interactions on television, 58 percent depict no pain, 47 percent depict no harm, and 40 percent depict harm unrealistically. Of all violent scenes on televi-
The NTVS random ly sampled programs from 6:00 a.m. to 11:00 p.m. on 23 broadcast and cable channels over a 20-week period from O ctober to June during the 1994 through 1997 view ing seasons. A sum o f 119 hours per channel, or 2,500 hours o f television programming was assessed each year.
The NTVS defined violence as "overt depiction o f a credible threat o f physical force, or the actual use o f such force intended to physically harm an animate being or group o f beings." Content analyses o f television programs generally treat the program itself as the unit o f analysis and exclude advertisements."Violence also includes certain depictions o f physically harmful consequences against an animate being or group that occur as a result o f unseen violent means. Thus, there are three prim ary types o f violent depictions: credible threats, behavioral acts, and harmful consequences (Smith & Donnerstein, 1998, p. 170).
sion, 86 percent feature no blood or gore. Only 16 per cent of violent programs feature the long-term, realis tic consequences of violence.

# M a jo r B e h a v io r a l Effe c t s o f M e d ia V io l e n c e
Because an exhaustive description of the research lit erature is not possible within this brief discussion, findings from meta-analyses are reported3 where available. In meta-analyses, the results of multiple studies are combined and compared systematically and an overall effect size computed. These analyses include findings from randomized experiments that look at aggression immediately after viewing vio lence, as well as cross-sectional surveys that provide a snapshot of the relationship between viewing violence and behavior at a fixed point in time. Also presented are findings from longitudinal studies that examine whether exposure to media violence affects violence and aggression over time.

# Television and Film Violence
Many anecdotal reports have described instances in which television and film violence led to immediate violent behavior in individual children, but scientific studies of this relationship draw a more complex and qualified picture. Most of the relevant research has focused on how watching dramatic violence on televi sion and film affects aggressive thoughts and emo tions, as well as aggressive behavior. Some important studies address violence as well.

# Experimental Studies
A substantial number of laboratory and field experi ments over the past half-century have examined whether children exposed to violent behavior on film or television behave more aggressively immediately afterwards (see reviews by Bushman & Huesmann, 2000;Comstock & Scharrer, 1999;Geen, 1990;Geen & Thomas, 1986;Huesmann et al., 1997). Many stud ies have also examined the immediate effect of media violence on aggressive thoughts or emotions (Rule & Ferguson, 1986), which have been shown to increase the risk of aggressive behavior (Dodge & Frame, 1982;Huesmann & Guerra, 1997).
The most recent and comprehensive meta-analy sis of media violence was conducted by , who examined effect sizes from 217 empirical studies on media violence and aggres sive and violent behavior published between 1957 and 1990. The analysis indicates clearly that brief expo sure to violent dramatic presentations on television or in films causes short-term increases in the aggressive behavior of youths, including physically aggressive behavior. Across all the randomized experiments, the unweighted average effect size was large (r = .37).4 When only experiments examining physical aggres sion as the outcome were examined, the effect size was also large (r = .32).
Although the experimental methods used in these studies enable researchers to test causality more read ily than other research methods as noted by Comstock and Paik (1991), the findings may not necessarily apply to all real-world settings. Because experiments are narrowly focused on testing specific causal hypotheses, they do not examine the effects of all fac tors that might be present in more realistic situations. This means that some real-world influences might actually lessen or even eliminate the aggressive reac tions observed in experiments. For example, while tel evision, film, and other media contain a variety of antisocial and other messages, most laboratory studies to date have exposed study participants primarily to violent materials. In addition, participants may react differently in the laboratory when they realize that their expressions of aggression will not be punished (Gunter, 1983). Any summary of these experimental results should also acknowledge the argument raised by some critics (such as Freedman, 1992) that many study participants provide the responses they believe the researcher wants. Despite these limitations, labo ratory experiments are important because they allow researchers to isolate the unique effect of exposure to violence on subsequent behavior.
An important general finding from these experi mental studies is that not all youths seem to be affect ed equally by media violence. Effects seem to be strongest on youths who are predisposed to be aggres sive for some reason or who have been aroused or provoked (Berkowitz, 1993;Bushman, 1995;Geen & O'Neal, 1969).

# Cross-Sectional Surveys
Cross-sectional surveys over the past 40 years have generally focused on establishing a link between the current aggressiveness of children and the amount of television and film violence they watch regularly (see reviews by Bushman & Huesmann, 2000;Chaffee, 1972;Comstock & Scharrer, 1999;Eysenck & Nias, 1978;Huesmann & Miller, 1994). Paik and Comstock's meta-analysis (1994) indi cates that in cross-sectional surveys viewing media violence was positively correlated with various meas ures of aggression. They reported small to moderate effect sizes across all measures of aggression (r = .19) and for physical aggression alone (r = .20). For the outcome of most concern to this report-criminal vio lence against a person-the effect size was small (r = .06). These results suggest that the link between media violence and aggressive behavior found in laboratory studies may also hold for behaviors outside the labo ratory. However, cross-sectional surveys do not by themselves indicate whether media violence is caus ing aggression, whether aggressive youths are attract ed to media violence, or whether some other factor is predisposing some youths to watch more violence and behave more aggressively.

# Longitudinal Studies
Long-term studies in which exposure to media vio lence in early childhood is related to later aggression and violence (such as aggravated assault, robbery, rape, and homicide) can identify the enduring effects of media violence. In most such studies to date, how ever, aggression, not violence, has been the primary outcome measured. In the absence of a meta-analysis, the findings of three frequently cited longitudinal studies on the effects of media violence are discussed briefly below. Studies examining effects over shorter time periods (Singer et al., 1984) or with internation al samples (Huesmann & Eron, 1986) are not includ ed here.
In a study begun in 1960 on a sample of 875 youths in New York State, Eron and colleagues found that for boys, but not for girls, exposure to media vio lence at age 8 was significantly related to aggressive behavior a decade later (r = .31, N = 211, p < .01) (Eron et al., 1972;Lefkowitz et al., 1977). At both times, peers assessed physical and verbal aggression. The longitudinal correlation remained above .25, even in separate analyses statistically controlling for factors such as the child's initial aggressiveness, the child's intelligence, family SES, parents' aggressiveness, and parents' punishment and nurturance of the child.  examined the probability of initiating aggression after exposure to violence on television in 2,400 boys and girls age 7 to 12 from two midwestem cities who had been surveyed up to six times between 1970 and 1973. A sample of 800 teenage boys5 was studied at five times to identify the effect of violent television on aggression and vio lence. For the elementary school sample, the average cross-sectional correlation between exposure to media violence and personal aggression was small for boys (r = .17) and large for girls (r = .30). The researchers then attempted to predict aggressive behavior at one point in time from the extent to which children viewed television violence at an earlier time, while controlling for earlier aggressive characteris tics. They examined this prediction over 15 time intervals ranging from 5 months to 3 years apart. For elementary school boys, only 2 of the 15 predictions at different intervals were statistically significant. For girls, only three predictions were statistically signifi cant. In the teenage male sample, only one of eight correlations was significant. In only one of nine analyses using measures of violence (for example, knife fight, car theft, mugging, gang fight) were boys with greater exposure to television violence more likely to initiate violence 2 years later than those with less exposure.
The third longitudinal study of media violence effects began in the late 1970s and spanned five coun tries (Huesmann et al., submitted;Huesmann et al., 1984;Huesmann & Eron, 1986). In each locale, sam ples of middle-class youths were examined three times between age 6 to 8 or age 8 to 11. Both physical and verbal aggression were assessed by peers. The correlations between aggression and overall viewing of television violence at a single point in time were small to moderate and often significant. In the United States, the 3-year average correlation was moderate for boys and for girls (r = .25 and r = .29, respective ly; p < .001). The predictive power of viewing televi sion violence for childhood aggression a year later varied substantially. In the United States, girls' view ing of television violence had a significant effect (P = .17, N = 89, p < .05) on their later aggression, even after accounting for early levels of aggression, SES, and scholastic achievement. For boys, television vio lence alone did not predict later aggression. When the investigators took into account both exposure to tele vision violence and identification with aggressive tel evision characters, they found a positive relation with aggressiveness (P = .19, N = 84, p < .05).
A follow-up study of over 300 people in the U.S. sample 15 years later suggested that media violence has a delayed effect on aggression (Huesmann et al., submitted). There was a small to moderate longitudi nal correlation between childhood television viewing and a composite measure of young adult aggression (physical, verbal, and indirect aggression) for both men (r = .21, N = 153, p < .01) and women (r = .19, N = 176, p < .01). When the outcome was limited to physical aggression, the correlations were smaller (r = .17 and r = .15, respectively). Furthermore, women who had watched relatively more television violence as girls committed significantly more specific acts of violence as adults, such as "punching, beating, or choking another adult," than did the other women (17 percent versus 4 percent). There were no significant differences among the men. Other analyses showed th a t e ffe c ts rem ain ed s ig n ific a n t ev en w hen researchers controlled for parent education and chil dren's scholastic achievement (P = .19 for boys, P = .17 for girls, p < .05). In addition, aggressive behavior did not significantly increase boys' or girls' viewing of television violence (P = .08 for boys and P = .04 for girls; p = ns).
In summary, these longitudinal studies show a small, but often statistically significant, long-term relationship between viewing television violence in childhood and later aggression, especially in late ado lescence and early adulthood. Some evidence suggests that more aggressive children watch more violence, but the evidence is stronger that watching media vio lence is a precursor of increased aggression.

# Other Studies
Other studies have explored the behavioral impact of introducing television in several countries (Centerwall, 1989a(Centerwall, , 1989b(Centerwall, , 1992Joy et al., 1986;Williams, 1986). These studies indicate that when tel evision was introduced, aggression and violence increased. The findings must be viewed with caution, however, because they do not take into account a range of other factors that may influence national crime rates and the amount of violence watched on television.
Despite anecdotal reports of a "contagion of vio lence," relatively little systematic research has exam ined whether seeing or hearing about violence in news coverage encourages violent or aggressive behavior. On the whole, the limited data available support the notion of a contagion effect. This evidence is derived from studies examining how reports of a well-known person's suicide affect the likelihood of imitative sui cide (Phillips, 1979(Phillips, ,1982Simon, 1979;Stack, 1989). Other studies of the contagion effect (Berkowitz & Macaulay, 1971;Phillips, 1983) have been questioned because of their research methods and the ambiguity of their results (Baron & Reiss, 1985; see Phillips & Bollen, 1985 for a response). This area merits addi tional research.

# Violence in Other Media

# Internet
Theoretically, the effects of exposure to media vio lence extend to Internet media as well. To date, how ever, no studies have been published regarding the effects of Web-based media violence on youth aggres sion and violence.

# Music Videos
A relatively small amount of research has focused on the impact of music videos with violent or antisocial themes (Baxter et al" 1985;Caplan, 1985;Hansen & Hansen, 1990;Johnson et al" 1995aJohnson et al" , 1995bRich et al" 1998). Randomized experiments indicate that exposure to violent or antisocial rap videos can increase aggres sive thinking, but no research has yet tested how such exposure directly affects physical aggression.

# Youth Violence: A Report of the Surgeon General

# Video Games
The impact of video games containing violence has recently become a focus of research because children are theoretically more susceptible to behavioral influ ences when they are active participants than when they are observers. To date, violent video games have not been studied as extensively as violent television or movies. The number of studies investigating the impact of such games on youth aggression is small, there have been none on serious violence, and none has been longitudinal.
A recent meta-analysis of these studies found that the overall effect size for both randomized and corre lational studies was small for physical aggression (r = .19) and m oderate for aggressive thinking (r = .27) (Anderson & Bushman, in press). In separate analyses, the effect sizes for both randomized and cross-sectional studies was small (r = .18 and .19, respectively). The impact of video games on violent behavior remains to be determined.

# Potential Moderators of Behavioral Effects
Research suggests that not all youths are affected in the same way by viewing media violence. Factors that appear to influence the effects of media violence on 0 aggressive or violent behavior include characteristics of the viewer (such as age, intelligence, aggressive ness, and whether the child perceives the media as realistic and identifies with aggressive characters) and his or her social environment (for example, parental influences), as well as aspects of media content (including characteristics of perpetrators, degree of realism and justification for violence, and depiction of consequences of violence).
Evidence that these factors moderate the influence of media violence is limited, and it is more relevant to aggression than to violence. For example, studies of responses to violent television and films and violent video games have found that people who were initially more aggressive than other subjects were more affected in behavior, thoughts, and emotions (Anderson & Dill, 2000;Bushman, 1995;Bushman & Geen, 1990;Friedrich & Stein, 1973;Josephson, 1987). Research in this area clearly suggests that the impact of violent tel evision, film, and video games on aggression is moder ated by viewers' aggressive characteristics.
Evidence that other individual, environmental, and content factors moderate the effects of exposure to media violence is less clear. Some studies suggest that these factors may buffer or enhance effects, but few have tested for such influences. Although limited in scope and depth, such studies provide clues to potential avenues for prevention efforts. For example, preliminary data point to the potentially vital role of parents in supervising their children's exposure to violent media and in helping them interpret it (Nathanson, 1999).

# S u m m a r y o f M ajor Empirical Research Fin d in g s
A substantial body of research now indicates that expo sure to media violence increases children's physically and verbally aggressive behavior in the short term (within hours to days of exposure). Media violence also increases aggressive attitudes and emotions, which are theoretically linked to aggressive and vio lent behavior. Findings from a smaller body of longi tudinal studies suggest a small but statistically signifi cant impact on aggression over many years. The evi dence for long-term effects on violence is inconsistent.
Based on the findings of studies reported here, the average effect sizes of exposure to media violence on various measures of aggression range from small (r = .15) to quite large (r = .64). The evidence that exposure to media violence is a risk factor for violent behavior is more limited, with small average effect sizes of r = .06 in cross-sectional surveys, r = .13 in experimental studies , and r = .00 to .22 in longitudinal studies (Huesmann et al., submitted;. Taken together, findings to date suggest that media violence has a relatively small impact on violence. The effect on aggression is stronger, ranging from small to moderate.
Although there is clear scientific evidence of a correlation between exposure to media violence and some violent behaviors, randomized experimentsthe research methodology best suited to determining causality-cannot ethically be used in studies of vio lent behavior. Thus, the causal links between media violence and behavior are more firmly established for aggressive behavior than for violent behavior. Longitudinal studies, which also provide some insights into this issue, have linked repeated exposure to media violence in the early, years with an increased likelihood of aggressive behavior in the teen and adult years. However, few of these studies have reported on violence as an outcome. Moreover, the violent behav iors that are the focus of this report (homicide, forcible rape, aggravated assault,, and robbery) occur infrequently and are subject to multiple influences. At present, it is extremely difficult to distinguish between the relatively small, long-term effects of media expo sure and those other influences.
In sum, a diverse body of research provides strong evidence that exposure to violence in the media can increase children's aggressive behavior in the short term. Some studies suggest that long-term effects exist, and there are strong theoretical reasons why this is the case. But many questions remain regarding the short-and long-term effects of media violence, espe cially on violent behavior.

# Preventive Efforts
Efforts to reduce the presumed harmful effects of media violence on youths have taken various forms, including:
- Attempting to reduce the amount of media violence and children's access to it (for example, calls for media self-regulation and violence ratings);
- Encouraging and facilitating parental monitoring of children's access to media (for example, V-chip leg islation and advisory labels on music and video games);
- Educating parents and children about the potential dangers of media violence (for example, media and empathy educational programs); and
- Targeting children's views about violence to reduce the chances that they will imitate the violence they see (Corder-Bolz, 1980;Hicks, 1968;Huesmann et al., 1983;Linz et al., 1990;Nathanson, 1999).
From a public health perspective, this preventive domain is largely uncharted territory. Few preventive efforts have been studied systematically. Furthermore, not enough research has been done to form a basis for the design of many experimental interventions. As noted in other parts of this report, an extensive body of scientific research undergirds our emerging knowledge about effective ways of preventing youth violence. Although many violence prevention programs address a complex array of risk and protective factors in the lives of young people, they have not yet addressed the role of the media. This gap needs to be filled.

# Im plic a tio n s
Research to date justifies sustained efforts to curb the adverse effects of media violence on youths. Although our knowledge is incomplete, it is sufficient to devel op a coherent public health approach to violence pre vention that builds upon what is known, even as more research is under way. Unlike earlier Federal research reports on media violence and youth (National Institute of Mental Health, 1982; U.S. Surgeon General's Scientific Advisory Committee on Television and Social Behavior, 1972), this discussion takes place within a broader examination of the caus es and prevention of youth violence. This context is vital. It permits media violence to be regarded as one of many complex influences on the behavior of America's children and young people. It also suggests that multilayered solutions are needed to address aggressive and violent behavior.
A variety of media violence is present in the homes of young children, with considerable variation in the degree of parental supervision (Woodard, 1998). Regardless of government and other interested groups' attempts to limit the amount of violence reaching American families, families themselves play a critical role in guiding what reaches their children. Whether by adopting V-chip technology for home tel evision programming, by using Internet violence screening, or simply by monitoring closely children's use of televisions, computers, and video games, par ents can limit and shape their children's selection of, interaction with, and response to media violence. Community groups-including schools, faith-based organizations, and Parent Teacher Associations-can teach parents and children how to be more critical consumers of media. Federal agencies can be more active in encouraging needed research, in sharing research findings with the public, in encouraging increased interaction between violence prevention researchers and media researchers, and in creating networks for sharing solutions to social and public health problems.   (Gallup, 1999). This per ception, combined with the increased lethality of youth violence in the early 1990s, has lent urgency to the search for effective violence prevention efforts. Hundreds of youth violence prevention programs are being used in schools and communities throughout the country, yet little is known about the actual effects of many of them (Gottfredson et al., 2000;Tolan & Guerra, 1994). Few such programs have been rigor ously evaluated, including many ongoing efforts (Elliott, 1998). The evaluations that have been done indicate that much of the money America spends on youth violence prevention is spent on ineffectivesometimes even harmful-programs and policies .
At the same time, researchers know much more today about how to prevent youth violence than they did two decades ago, when some declared that "noth ing works" to prevent violence Sechrest et al., 1979). This is clearly no longer the case. Over the past few decades, social scientists have made great strides in uncovering the causes and corre lates of youth violence.
Unfortunately, the news about effective programs has been slow to bring about change in school, com munity, and juvenile justice system prevention efforts, where precious resources continue to be spent on inef fective programs. Some experts believe that youth crime and violence rates could be "substantially" reduced simply by reallocating the money now spent on ineffective policies and programs to those that do work (Mendel, 2000, p. 1).
The strategy of using prevention resources to their fullest potential presents many challenges. The first lies in identifying effective prevention approaches and programs. Differentiating between effective and inef fective ones can be a difficult chore for schools, com munities, and juvenile justice authorities. Numerous agencies and organizations have published recom mendations on "what works" in youth violence pre vention, but in many cases there is little consistency regarding the specific programs they recommend. The reason for this inconsistency is a lack of uniformly applied scientific standards for what works.

# Pr o m o t in g H ealthy, N o n v io l e n t C h ildren
This chapter identifies a set of standards based on sci entific consensus and applies those standards to the literature on youth violence prevention in order to identify with confidence general strategies and pro grams that work, that are promising, or that do not work to prevent youth violence. This information can be used by schools, communities, juvenile justice agencies, program funders, and others interested in youth violence prevention to aid their programming decisions. With this information in hand, it may be possible to fulfill the prediction that better use of existing prevention resources can substantially reduce the problem of youth violence.
The first section of this chapter describes the methods used in this report to identify best practices in youth violence prevention. The second describes cur rently accepted scientific standards for determining program effectiveness. The third section applies those standards to the existing youth violence prevention lit erature and presents findings on best practices-what
works, what is promising, and what does not work. The information in that section is based on currently available research and is not intended to be the final word on the subject. As more programs are evaluated, the standards outlined in this report can be used to identify additional programs and strategies that work in preventing youth violence.
The fourth section, on cost-effectiveness, is intended to enhance the information provided in the best practices section by adding another dimension to the determination of what works. The conclusion dis cusses the need to take the next step in preventing youth violence by learning how to preserve the bene fits of successful prevention programs when imple menting them on a national scale.

# M e t h o d s o f Identifying Best P ractices
Identifying the best practices for preventing youth vio lence involves two approaches, each with its own lim itations. The first is meta-analysis, a rigorous statistical method of combining the results of several studies to obtain more reliable estimates of the effects of a gen eral type of treatment or intervention. This quantitative approach can be used to summarize program evalua tion evidence and draw overall conclusions about the strength and consistency of the influence, or effect size, that particular types of programs have on violent behavior. In the field of youth violence, meta-analysis has been used primarily for evaluations of interven tions with violent or delinquent youths.
The second, less empirical approach is to review the evaluation research and identify the general strate gies that characterize effective programs. While such reviews are not quantitative, they are more easily con ducted than meta-analyses, and they offer useful information for generating hypotheses and drawing general conclusions about the effectiveness of various strategies for preventing youth violence.
In identifying best practices, this report relies heav ily on recently published reviews and focuses mainly on strategies and programs with demonstrated effects on youth violence and on the major risk factors for youth violence.
Strategies and programs are first classified as effective or ineffective. Effective strategies and pro grams are then further broken down into Model pro grams, which meet very high standards of demon strated effectiveness, and Promising programs, which meet a minimum standard. Finally, within Model and Promising categories, a distinction is made between strategies and programs that have demonstrated effects on violence and serious delinquency (Level 1) and those that have demonstrated effectiveness on known risk factors (Level 2).
The decision to include serious delinquency along with violence as a criterion for Level 1 pro grams was based upon the major meta-analysis of program effectiveness (Lipsey & Wilson, 1998), which did not differentiate between those two out comes. Serious delinquency was a major risk factor for violence in both the early and late onset of risk (see Chapter 4). Level 2 Model programs are those that address any of the other risk factors with large effect sizes (substance use, weak social ties, antiso cial or delinquent peers, gang membership).1 For Promising strategies, Level 1 again refers to pro grams with demonstrated effects on violence and serious delinquency. Level 2 programs are those with demonstrated effects on any risk factor with an effect size of .10 or greater.
No attempt was made to systematically search the literature for programs and strategies that affect small risk factors for youth violence, such as academic fail ure or anxiety and depressive disorders. Therefore, some effective programs or strategies that target small risk factors may not be included. However, such pro grams and strategies occasionally came to our atten tion; those that did were included if the risk factors they affected had an effect size of .10 or greater. Thus, risk factors such as child abuse and neglect, which have an effect size of less than .10, are not covered in this report.2 Also excluded are clinical trials of psy chotropic medications, which have proved effective in treating some affective disorders that are risk factors for youth violence but have not been shown in rigorous clinical studies to reduce youth violence specifically. A review of these interventions can be found in Mental Health: A Report o f the Surgeon General (1999).
Several major reviews of youth violence preven tion and intervention programs have been published in the past decade. This chapter draws mainly upon the following:3
- Preventing Crime: What Works, What Doesn't, What' s Promising. A Report to the United States Congress (Sherman et al., 1997) - The Office of Juvenile Justice and Delinquency Prevention's A Sourcebook: Serious, Violent, and Chronic Juvenile Offenders (Howell et al., 1995) - The Office of Juvenile Justice and Delinquency Prevention's Guide fo r Implementing the Comprehensive Strategy for Serious, Violent, and Chronic Juvenile Offenders (Howell, 1995) - The Centers for Disease Control and Prevention's Best Practices o f Youth Violence Prevention: A Sourcebook for Community Action (Thornton et al.,
- The American Youth Policy Forum's Less Hype, More Help: Reducing Juvenile Crime, What Works-And What Doesn' t  - The Center for the Study and Prevention of Violence's Blueprints fo r Violence Prevention  - "School-Based Crime Prevention" (Gottfredson et al., in press) To improve readability, the reviews listed above are cited here and in the section below on scientific standards for effectiveness, but they are not referred to repeatedly in the section on best practices. Citations not listed above will be included where appropriate.
Many reviews use either no explicit criteria or only minimal criteria for identifying the programs they rec ommend, making it difficult to draw clear conclusions about the effectiveness of individual violence preven tion strategies. This report limits its identification of effective programs to those meeting a minimum stan dard of study design similar to the maximum standard described in Sherman et al. (1997) and Gottfredson et al. (in press). In those two reports, a scientific methods score of 4 or 5 indicates that an evaluation used an experimental or quasi-experimental design. This report applied that design standard to the extent possible, given the limitations described above.
This report also attempts to distinguish between absolute deterrent effects, in which an intervention is compared to no treatment, and marginal deterrent effects, in which the intervention or strategy is evalu ated against another treatment. Marginal deterrent effects are effects of the intervention over and above the effects of another treatment strategy and thus may underestimate the true effects of the intervention, com pared to receiving no treatment at all. In such cases, the nature of the comparison group is identified in the text.
Both meta-analyses and reviews can be used to identify successful strategies, approaches, or types of programs used to prevent youth violence. However, this general approach has a critical limitation: Within any given category of programs, there may be specif ic programs that are effective and others that are not; moreover, programs may be effective for some popu lations but not others (males but not females, for example). The general effect size is an estimate of the average effect and thus may not characterize any par ticular program or its use for a particular population. Often the effects of individual programs within each general strategy vary widely. For this reason, it is necessary to take one more step in the identification of best practices-focusing specifically on individual programs that work.
Identifying specific programs that work requires a clear set of standards for judging effectiveness. This chapter describes the scientific community's consen sus regarding standards and how this report applied those standards to the evaluation literature to place programs in one of three categories: Model (demon strates a high level of effectiveness), Promising (meets minimal standards of effectiveness), or Does Not Work (consistent evidence of no effects or harmful effects).
Few existing violence prevention and intervention programs have met the qualifications of a Model pro gram. Many more have met the standards for a Promising program, and even more would probably meet these standards if evaluated appropriately. The fact that a program is not identified in this report as Promising or Model does not mean it is ineffective; in most cases it means only that it has not been rigorous ly evaluated. Those evaluated and found to be ineffec tive are identified as ineffective. While hundreds of programs are employed throughout the United States to prevent youth violence and treat young offenders, only those with a credible scientific evaluation are highlighted in this report. This shortfall underscores the need for a renewed focus on evaluation in the field of youth violence prevention.

# Scientific St a n d a r d s for D eterm inin g Pro g r a m Effectiveness
The scientific community agrees on three standards for evaluating effectiveness: rigorous experimental design, evidence of significant deterrent effects, and replication of these effects at multiple sites or in clini cal trials. For example, the level of evidence required to establish the effects of an agent or intervention in Mental Health: A Report of the Surgeon General (1999) was demonstration of the effects in random ized, controlled experimental studies that had been replicated. The U.S. Food and Drug Administration requires the same level of evidence before approving a new drug for use in humans. Unfortunately, this level of evidence has not been routinely required by agen cies that recommend or fund youth violence preven tion programs, though some organizations and most researchers are calling for establishment of meaningful 0 criteria for program effectiveness (Elliott, 1998;Mendel, 2000, p. 74). Most researchers want evalua tions to meet one or more of these three scientific stan dards for assessing effectiveness.
Rigorous experimental design includes, at a mini mum, random assignment to treatment and control groups (Andrews, 1994;Center for Substance Abuse Prevention, 2000;Chamberlain & Mihalic, 1998;Howell et al., 1995;Lipsey, 1992a;Lonigan et al., 1998). A less stringent, but acceptable, study design is quasi-experimental, in which equivalent comparison and control groups are established but assignment of study participants to the groups is not random (Center for Substance Abuse Prevention, 2000; Howell et al., 1995;Lipsey, 1992b;Sherman et al., 1997;Tolan & Guerra, 1994).
Well-designed studies should also have low rates of participant attrition, adequate measurement, and appropriate analyses (Andrews, 1994;Center for Substance Abuse Prevention, 2000;Chamberlain & Mihalic, 1998). High attrition can undermine the equivalence of experimental and control groups. It can also signal problems in program implementation. Adequate measurement implies that the study meas ures, including the outcome measure, are reliable and valid indicators of the intended outcomes and that they are applied with quality, consistency, and appro priate timing (Tolan & Guerra, 1994).
In clinical trials, replication means conducting both efficacy and effectiveness trials (Lonigan et al., 1998). Efficacy trials test for benefits to participants in a con trolled, experimental setting, and effectiveness trials test for benefits in a natural, applied setting. In practice, this distinction is often blurred, but the principle of independent replication at multiple sites is well estab lished. Replication is an important element of program evaluation because it establishes that a program and its effects can be exported to new sites and implemented by new teams under different conditions. A program that is demonstrated to be effective at more than one site is likely to be effective at other sites as well.
Statistical significance is based on the level of confidence with which one can conclude that a differ ence between two or more groups (generally a treat ment and a control group) results from the treatment delivered and not, for example, from the selection process or chance. A probability value of .05 is wide ly accepted as the threshold for statistical significance; a probability below this threshold (p < .05) indicates that a difference of this magnitude could happen by chance less than 5 percent of the time.
High-quality evaluations of youth violence pre vention programs should be designed to demonstrate with this degree of confidence that a program is reduc ing the onset or prevalence of violent behavior or indi vidual rates of offending (Andrews, 1994;Tolan & Guerra, 1994). Since serious delinquency is strongly related to violence, reductions in serious criminal behavior (or index crimes) are also considered to be acceptable outcome measures for identifying effective violence prevention programs (Andrews, 1994;Elliott, 1998;Lipsey, 1992aLipsey, , 1992b. However, direct scientific evidence of a deterrent effect on violent behavior is certainly preferable.
Prevention programs are designed to prevent or reduce violent behaviors by acting on risk and protec tive factors. Reducing risk is a less stringent standard than reducing violence, but reducing risk undoubtedly holds some promise of preventing violence. Thus, sig nificant changes in risk factors for violence are acceptable indications of program effectiveness Gottfredson et al., in press;Howell et al., 1995;Sherman et al., 1997). In addition, because most violence begins in adolescence, child hood interventions are concerned primarily with risk reduction.
A less widely accepted but nevertheless important standard for demonstrating effectiveness is long-term sustainability of effects . Although this criterion may not be required to estab lish effectiveness in other disciplines, it is very impor tant in evaluating violence prevention programs because beneficial effects can diminish quickly after youths leave a treatment setting or program to return to their usual environment.
Effective programs produce long-term changes in individual competencies, environmental conditions, and patterns of behavior. Thus, successful programs get youths off a violent life course trajectory. The sus tainability of effects is particularly difficult for early intervention programs, which can be implemented more than a decade before the peak age of onset for youth violence. Ideally, effects would be sustained though adolescence. On a practical level, programs in this report are considered to have demonstrated sus tainability if the effects of the intervention continue for at least a year after treatment or participation in the designed intervention, with no evidence of a subse quent loss of effect .
Higher standards should be set for programs that are promoted and disseminated on a national level than for those being developed and implemented on a more restricted basis at the local level. Before a program is recommended and funded for national implementation, it is important to show clearly that it has a significant, sustained preventive or deterrent effect and that it can be expected to have positive results in a wide range of community settings (as long as it is implemented cor rectly and with the appropriate population). Programs that meet such high standards are designated Model programs. Those that do not quite meet these rigorous standards are recognized and encouraged as Promising, with the caution that they be carefully evaluated.
Identifying ineffective programs is another ele ment of assessing best practices. It is as important to know which programs do not work-and should not be supported with limited prevention funds-as it is to know which do work. The same scientific stan dards are used in judging effectiveness and ineffec tiveness. Because it is generally unlikely that a highquality evaluation will be conducted on a program that shows little sign of effectiveness, only two spe cific programs have been designated Does Not Work in this report. Some general strategies identified as ineffective in this report may not actually be flawed; rather, their lack of effectiveness may result from poor program implementation or a poor match between program and target population. Alternatively, some approach es may appear ineffective when used in isolation because their effects are quite small and difficult to detect. These approaches should not be used alone, but they may be useful as components of more com prehensive strategies that have positive preventive effects. In other cases, however, a program or approach may be ineffective because the basic strate gy is flawed-that is, the method or approach used to change the targeted risk or protective factors does not have the intended effect.
The following is a summary of the scientific stan dards for establishing the effects of a violence preven tion program.

# Model
- Rigorous experimental design (experimental or quasi-experimental)
- Significant deterrent effects on:
-Violence or serious delinquency (Level 1)
-Any risk factor for violence with a large effect size (.30 or greater) (Level 2)
- Replication with demonstrated effects
- Sustainability of effects

# Promising
- Rigorous experimental design (experimental or quasi-experimental)
- Significant deterrent effects on:
-Violence or serious delinquency (Level 1)
-Any risk factor for violence with an effect size of .10 or greater (Level 2)
- Either replication or sustainability of effects

# Does Not Work
- Rigorous experimental design (experimental or quasi-experimental)
- Significant evidence of null or negative effects on violence or known risk factors for violence
- Replication, with the preponderance of evidence . suggesting that the program is ineffective or harmful Youth Violence: A Report of the Surgeon General Other standards have been proposed for youth violence prevention programs, particularly those intended for implementation on a national level. One of these is cost-effectiveness, a key consideration in program funding but not a scientific criterion for effectiveness. Unfortunately, there are no standardized cost criteria for violence prevention programs, so it is difficult to compare costs across programs (Elliott, 1998). Moreover, it is difficult to obtain reliable costbenefit estimates for individual programs. Despite these obstacles, some researchers have conducted extensive reviews of the costs and benefits of violence and delinquency prevention and in terv en tio n p ro gram s (G reenw ood, 1995;G reenw ood et al., 1998;K aroly et al., 1998;Washington State Institute for Public Policy, 1999). Their findings will be discussed in the cost-effectiveness section of this chapter. This is an important and growing area of research.
Setting such stringent scientific standards auto matically limits the number and types of programs that will be identified as effective in this report. The spe cific programs that can meet these standards will be determined in part by the nature of the program-the design must lend itself to scientific evaluation-and in part by whether funding has been made available for program evaluation. For instance, early childhood individual change programs are overrepresented in the list of effective programs. This fact is probably a result of the relatively large amount of funding allocated to the study of these programs and the relative ease with which experimental evaluations can be carried out. On the other hand, programs promoting change in the social structure, community-level programs, and pro grams that focus on environmental change more gen erally (in schools, neighborhoods, peer groups, and so on) are probably underrepresented in this report. Evaluation of such programs and strategies is more dif ficult and costly; therefore, fewer rigorous evaluations of these programs have been done.
Because of these limitations, the programs dis cussed in this report may not represent the overall bal ance of youth violence prevention programs currently being implemented in communities throughout the country. This shortcoming highlights the need for more research on program effectiveness and for the development of additional criteria and valid measures for assessing the effects of community-or schoolbased and environmental change programs. In addi tion, the imbalance should not be interpreted as an indication that such programs are less effective than programs that focus on individual change. Indeed, there is some evidence that school-based programs designed to change the social climate of the classroom or school are more effective than individual change programs (Gottfredson et al., in press).

# St a t e g ie s a n d P r o g r a m s : M o d e l , P r o m is in g , a n d D o e s N o t W o r k
It is important to reiterate that the specific programs and general strategies discussed in this report have been identified from recent reviews of the literature on youth violence prevention. Although this information is growing rapidly, youth violence prevention remains a young field, and only limited evaluation data are available for many strategies and programs. Therefore, the absence of a particular strategy or program from this section does not in any way imply that it is inef fective; rather, the information available is not suffi cient to justify any conclusions about its effectiveness.
Model and Promising programs meet the scientif ic criteria for effectiveness outlined above within the populations in which they have been tested (as indi cated in the text). These programs are widely regard ed by the youth violence prevention community as effective. Appendix 5-A shows the consistency with which they have been recommended by various inde pendent groups of researchers as best practices in youth violence prevention. With only a few excep tions, each of the programs has already been identified as a best practice in two or more other reports on what works in youth violence prevention.
This section is divided into prevention and inter vention efforts. True prevention, or primary preven tion, is defined in this report as lessening the likeli hood that youths in a treatment or intervention pro gram will initiate violent behavior, compared to youths in a control group. In some cases, the preven tion of risk factors for violent behavior is considered the outcome, and the reduced likelihood of youths' encountering this risk is the measure of effective ness. Therefore, prevention programs are designed to target youths who have not yet become involved in violence or encountered specific risk factors for vio lence. Prevention efforts include general strategies and programs that target general (universal) popula tions of youths.
Intervention, on the other hand, is defined as reducing the risk of violence among youths who dis play one or more risk factors for violence (high-risk youths) or preventing further violence or the escalation of violence among youths who are already involved in violent behavior. These types of interventions are also known as secondary and tertiary prevention, respec tively. Thus, intervention includes programs that target high-risk (selected) populations of youths or already violent (indicated) youths. Although there is some overlap between prevention and intervention efforts, programs that are most effective in general populations of young people are not always effective in reducing further violence among seriously delinquent youths.
The programs discussed below are listed in Appendix 5-B, along with more detailed information on each one. Specific results of the evaluations are found there; findings are described in general terms in this chapter. Box 5-1 summarizes effective and inef fective strategies, and Box 5-2 lists the programs dis cussed below by best practices category: Model, Promising, or Does Not Work.

# Primary Prevention: General Populations of Young People
All of the programs and strategies discussed in this section are primary prevention approaches to reduc ing youth violence-that is, they are implemented on a universal scale and aim to prevent the onset of youth violence and related risk factors. Some are designed to change individual risk factors, others tar get environmental risk factors, and a few are designed to change both.

# Skill-and Competency-Building Programs
Skills-oriented programs are among the most effective general strategies for reducing youth violence and risk factors for youth violence. In fact, two universal pro grams that take this approach have met the criteria for a Model program: Life Skills Training and the Midwestern Prevention Project.
Life Skills Training (LST) is designed to prevent or reduce gateway drug use. The program targets stu dents in middle or junior high school, with initial implementation in grades 6 and 7 and booster sessions for the next 2 years. The curriculum has three major components: self-management skills, social skills, and information and skills related specifically to drug use. Teachers use a variety of techniques, including instruction, demonstration, feedback, reinforcement, and practice, to train students in these three core areas. Evaluations show that the program can cut tobacco, marijuana, and alcohol use. Moreover, long-term effects of participation in Life Skills Training include a lower risk of polydrug use, pack-a-day smoking, and inhalant, narcotic, and hallucinogen use.
The Midwestern Prevention Project targets middle school students (grades 6 or 7). Its goal is to reduce the risk of gateway drug use associated with the transition from early adolescence to middle through late adoles-cence by training youths to avoid drug use and situa tions in which drugs are likely to be used. The program has five major components that are implemented in stepwise fashion over the course of approximately 4 years: mass media program, school program, parent education and organization, community organization, and local health policy. The mass media program spans the duration of the project, while the other components are introduced at a rate of approximately one per year. The school-based component forms the core of the pro gram. This project has demonstrated positive effects on a number of outcomes that are closely related to youth violence. For instance, it has been shown to reduce daily smoking and marijuana use and to lessen mari juana use, hard drug use, and smoking through age 23.
In addition, the project has facilitated improvements in parent-child communication about drug use and in the development of prevention programs, activities, and services within communities.
Two school-based programs that focus on teaching important social skills to students, Promoting Alternative Thinking Strategies and I Can Problem Solve, meet the criteria for a Promising program. The Promoting Alternative Thinking Strategies (PATHS) curriculum is taught to elementary school students at entrance through grade 5. Lessons targeting emotional competence (expression, understanding, and regula tion), self-control, social competence, positive peer rela tions, and interpersonal problem-solving skills are deliv ered three times a week in 20-to 30-minute sessions. Evaluations of PATHS show that this program has posi tive effects on several risk factors associated with vio lence, including aggressive behavior, anxiety and depression, conduct problems, and lack of self-control. The effectiveness of PATHS has been demonstrated for both regular-education and special-education students.
I Can Problem Solve has been used effectively with students in nursery school, kindergarten, and grades 5 and 6. The main goal of this program, which is implemented in 12 small-group sessions over 3 months, is to train children to use problem-solving skills to find solutions to interpersonal problems. In evaluations, I Can Problem Solve has improved class room behavior and children's problem-solving skills for up to 4 years after the end of the intervention. Whereas this program is appropriate for all children, it has been most effective with children living in poor, urban areas. drug and alcohol use. Children who participate in LIFT exhibit less physical aggression on the play ground, better social skills, and, in the long term, less likelihood of associating with delinquent peers, using alcohol, or being arrested.

# Behavior Management Programs
Strategies that take a behavioral approach to youth violence can also have positive, consistent effects on violence, delinquency, and related risk factors. The behavioral approaches shown to be effective in pre venting youth violence on a universal scale are gener ally school-based and include behavior monitoring and reinforcement of attendance, academic progress and school behavior, and behavioral techniques for classroom management.
Much of the evidence on the effectiveness of behavior monitoring and reinforcement comes from studies conducted by Bry and colleagues (Bry, 1982;Bry & George, 1979. These studies pro vide evidence' that interventions focusing on enhanc ing positive student behavior, attendance, and aca demic achievement through consistent rewards and monitoring can reduce substance use, self-reported criminal activity, and arrests, as well as enhance aca demic achievement in middle school students. In one study, for example, students exposed to this type of intervention were far less likely than students in a con trol group to have a delinquency record 5 years after the program.
Behavioral techniques for classroom manage ment are a general strategy for changing the classroom environment. According to a review by O ' Leary and O'Leary (1977), the best strategies for promoting pos itive classroom behavior are establishing clear rules and directions, use of praise and approval, behavior modeling, token reinforcement, self-specification of contingencies, self-reinforcement, and behavior shap ing. Several strategies aimed at reducing negative stu dent behaviors are also effective: ignoring misbehav ior, reinforcing behavior that is incompatible with negative behavior, relaxation methods, and using disciplinary techniques such as soft reprimands, time outs, and point loss and fines in token economies.

# 124'm
The Seattle Social Development Project is an excellent example of a program that includes classroom behavior management among its core components. The goal of this Model program is to enhance elementary school students' bonds with school and their families while decreasing a number of early risk factors for vio lence. Like other Model programs in this report, the ini tiative includes both individual and environmental change approaches and multiple components known to improve the effectiveness of violence prevention efforts. In addition to classroom behavior management, the components include child skills training and parent training, discussed later in this section.
Through these three components, which target prosocial behavior, interpersonal problem solving, academic success, and avoidance of drug use, the Seattle Social Development Project reduces the initia tion of alcohol, marijuana, and tobacco use by grade 6 and improves attachment and commitment to school. At age 18, youths who participated in the full 5-year version of this program have lower rates of violence, heavy drinking, and sexual activity (including multi ple sexual partners and pregnancy) and better aca demic performance than controls. The Seattle Social Development Project has been used effectively in both general populations of youths and high-risk children attending elementary and middle school.
Classroom behavior management is also a core component of three Promising programs: the Bullying Prevention Program, the Good Behavior Game, and the School Transitional Environmental Program. The Bullying Prevention Program targets students in ele mentary, middle, and junior high school. It begins with an anonymous student questionnaire designed to assess bullying problems in individual schools. Using this information, parents and teachers implement school-, classroom-, and individual-level interven tions designed to address the bullying problems iden tified in the questionnaire, including individual work with students identified as bullies and victims. At the classroom level, teachers and students work together to establish and reinforce a set of rules about behavior and bullying, creating a positive, antibullying climate. This program has both individual change and environ mental change objectives.
In elementary and junior high schools in Bergen, Norway, bullying problems were cut in half two years after the intervention. Antisocial behavior, including theft, vandalism, and truancy, also dropped during these years, and the social climate of the school improved. Replications have been conducted in England, Germany, and the United States, with similar effects.
Like the Bullying Prevention Program, the Good Behavior Game uses classroom behavior manage ment as the primary means of reducing problem behaviors. The Good Behavior Game targets elemen tary school children and seeks to improve their psy chological well-being and decrease early aggressive or shy behavior. While both of these programs can reduce antisocial behavior, their effects on violence and delinquency have not yet been measured.
This intervention has shown positive effects, as measured by teachers' reports of aggressive and shy behaviors in first-graders. Long-term evaluations show sustained decreases in aggression among boys rated most aggressive in first grade. Effects on vio lence and delinquency have not been measured.
The third Promising primary intervention pro gram that makes use of classroom behavior manage ment is the School Transitional Environmental Program, or STEP. STEP is based on the Transitional Life Events model, which postulates that stressful life events, such as transitions between schools, place children at risk of maladaptive behav ior. The program's goals are to reduce the stress and disorganization often associated with changing schools by redefining the role of homeroom teachers. Behavior management is used to create an environ ment that promotes academic achievement and reduces school behavior problems and absenteeism. Participation in this program has been shown to reduce substance use and delinquency while improv ing academic achievement and school dropout rates. The STEP program has been most successful with students entering junior and senior high schools in urban, predominantly nonwhite communities. The program is also effective with students at high risk of behavioral problems.

# Capacity-Building Programs
Several other school-level environmental approaches are effective in reducing youth violence and related outcomes. For instance, those that focus on building a school's capacity to plan, implement, and sustain pos itive changes can significantly reduce student delin quency and drug use. One program in which students were empowered to address school safety problems resulted in significant reductions in fighting and teacher victimization. Program Development Education is an example of this approach to reducing youth violence. It is a structured organizational devel opment approach used to help organize, plan, initiate, and sustain school change. This approach has demon strated positive effects on delinquency rates lasting at least 2 years into the program. evidence is not yet strong enough to classify the Boys and Girls Clubs and the Big Brothers Big Sisters of America programs as Model or Promising, it is strong enough to conclude that the general strat egy of these and similar programs is effective at reducing youth violence and violence-related out comes. For instance, evaluations of Boys and Girls Clubs have shown reductions in vandalism, drug trafficking, and youth crime. An evaluation of a Canadian after-school program demonstrated large reductions in arrests. Although this general strategy is included with the primary prevention efforts, it can also be considered a secondary prevention strategy, since the specific youth development programs list ed above are usually implemented in high-risk neighborhoods.

# Teaching Strategies
Two other school-based primary prevention strategies are effective at reducing the risk of academic failure, a risk factor for youth violence: continuous progress program s and cooperative learning. Continuous progress programs are designed to allow students to proceed through a hierarchy of skills, advancing to the next level as each skill is mastered. This approach has shown consistent, positive effects on academic achievement in elementary school students in seven separate evaluations.
Cooperative learning is another innovative envi ronmental change approach that can improve academ ic achievement in elementary school children. Quite different from continuous progress programs, cooper ative learning programs place students of various skill levels together in small groups, allowing students to help each other learn. Studies by Slavin (1989Slavin ( , 1990 show that this approach has positive effects on atti tudes toward school, race relations, attitudes toward mainstreamed special-education students, and aca demic achievement.

# Community-Based Programs
Community-based strategies can also affect youth violence at the universal level. One such strategy is positive youth development programs. While the

# Ineffective Primary Prevention Programs

# School-Based Programs
Some educational approaches that target universal populations have shown a consistent lack of effect in scientific studies. Peer-led programs, including peer counseling, peer mediation, and peer leaders, are among them. In a 1987 review of these interventions, Gottfredson concluded that there is no evidence of a positive effect and that these strategies can actually harm high school students. Results of a meta-analysis confirmed this finding, adding that adult-led programs are as effective as, or more effective than, peer-led programs in reducing youth violence and related risk factors. Nonpromotion to succeeding grades is another educational approach that can have harmful effects. Studies of this approach demonstrate negative effects on student achievement, attendance, behavior, and attitudes toward school.
One school-based universal prevention program meets the criteria for Does Not Work: Drug Abuse Resistance Education, or DARE. DARE is the most widely implemented youth drug prevention program in the United States. It receives substantial support from parents, teachers, police, and government fund ing agencies, and its popularity persists despite numerous well-designed evaluations and meta-analy ses that consistently show little or no deterrent effects on substance use. Overall, evidence on the effects of the traditional DARE curriculum, which is imple mented in grades 5 and 6, shows that children who participate are as likely to use drugs as those who do not participate. However, some positive effects have been demonstrated regarding attitudes toward police.
Researchers have suggested several reasons for DARE's lack of effectiveness. The program is most commonly criticized for its limited use of social skills training and for being developmentally inappropriate. Specifically, DARE is implemented too early in child development: It is hard to teach children who have not gone through puberty how to deal with the peer pressure to use drugs that they,will encounter in middle school.
Changes are being made at the national level in an attempt to improve the program's effectiveness. DARE developers have added social skills training sessions to the core curriculum and have developed a modified version of the curriculum that can be used in older student populations. These versions of DARE have not yet been evaluated.4

# Secondary Prevention: Children at High Risk of Violence
Secondary prevention programs and strategies are implemented on a selected scale, for children at enhanced risk of youth violence, and are aimed at pre venting the onset and reducing the risk of violence. Programs that target the families of high-risk children are among the most effective in preventing violence. Several family-based strategies and programs are included in the discussion below.

# Parent Training
One effective approach involves training parents to use specific child management skills. A review by Dumas (1989) shows that parent training can lead to clear improvements in children's antisocial behavior (includ ing aggression) and family management practices. In individual studies with disruptive/aggressive/hyperactive boys and girls, parent training has resulted in reduced aggressive, antisocial, and delinquent behav iors; lower arrest rates (including arrests for assault); less overall delinquency; and academic improvement. The following five Promising youth violence preven tion programs include parent-training components.
The Montreal Longitudinal Study, sometimes called the Preventive Treatment Program, is a 2-year intervention aimed at preventing delinquency among 7to 9-year-old boys from low-income families who have been identified as disruptive. The program has two major components: school-based social skills training (19 sessions) and parent training (17 sessions). The par ent-training sessions, provided every 2 weeks for the duration of the intervention, teach parents to read with their children, monitor and reinforce their children's behavior, use effective discipline, and manage family crises. A long-term follow-up of Canadian boys enrolled in this program found positive effects on academic achievement and avoidance of gang involvement, drug and alcohol use, and delinquency up to age 15.
The Syracuse Family Development Research Program targets parents and children in impover ished families. It provides weekly home visitation with parent training by paraprofessional child devel opment trainers and 5-year individualized day care that includes child training on social and cognitive skills and child behavior management. The Perry Preschool Program provides early education to chil dren age 3 and 4 from families with low socioeco nomic status. The preschool lasts 2 years and is designed to offer high-quality early childhood educa tion and promote young children's intellectual, social, and physical development. In addition, this intervention provides weekly home visits by teachers and referrals for social services, when needed. Both of these programs have demonstrated long-term effects (up to age 19) on delinquency, academic achievement, and other school-related outcomes. In addition, the Perry Preschool Program has produced significant reductions in antisocial behavior, serious fights, police contacts, and school dropout rates.
Parent training is one of a broad range of family services offered through Parent Child Development Center Programs, which target low-income families with children age 2 months to 3 years. The parent training component of this intervention targets moth ers as the primary caregivers and focuses on infant and child development, home management, and fami ly communication and interaction skills. The pro grams have positive effects on a variety of risk factors for youth violence, including child antisocial behavior and fighting and mother-child relationships.
The Parent-Child Interaction Training program targets low-income parents with preschool children who have at least one behavioral or emotional prob lem. Parents enrolled in the program participate in a series of four to five small-group sessions in which they learn a variety of parenting skills such as man agement of child behavior. This intervention has been shown to improve family management practices and reduce children's antisocial behaviors, including aggression and anxiety.

# Home Visitation
Another effective family-based approach to prevent ing youth violence is home visitation, in which a nurse or other professional goes to the child's home and pro vides training, counseling, support, monitoring, or all of these services to first-time, low-income, or other wise at-risk mothers. This strategy is particularly effective when implemented before children develop behaviors that put them at risk of violence.
Home visitation, with or without early childhood education programs, has shown significant long-term effects on violence, delinquency, and related risk fac tors in a number of studies. The degree of effect is dependent on several factors, including length (only long-term programs have demonstrated consistent effects), delivery (nurses appear to be the most effec tive home visitors, although some positive effects have been demonstrated with other types of visitors), and timing (the earlier these programs begin, the better).
Prenatal and Infancy Home Visitation by Nurses is the only home visitation program that meets the cri teria for a Model youth violence prevention program.

# O
It also incorporates all of the characteristics associat ed with the most effective home visitation programs: It is delivered by nurses, it begins early (before the child's birth), and it is long-term, lasting from before birth to age 2. Home visits are scheduled at intervals from 1 week to 1 month throughout the 2-year inter vention. The program targets low-income, at-risk pregnant women bearing their first child. The goals are (1) to improve pregnancy outcomes and child care, health, and development, (2) to build a social support network around the family, and (3) to enhance moth ers' personal development, including educational achievement, participation in the workforce, and per sonal competency skills and self-efficacy.
Prenatal and Infancy Home Visitation by Nurses has a number of long-term, positive effects on youth violence and related outcomes, including fewer arrests and less'alcohol use by youths at age 15 and lower rates of child abuse and neglect, compared to controls. While child abuse and neglect are not usually consid ered a violence outcome in this report, they are includ ed here because the intervention is designed for moth ers who are still youths themselves.

# Multicontextual Programs
Several Promising secondary youth violence preven tion programs address multiple contexts that affect a child's risk of future violence: home, school, and com munity. The Yale Child Welfare Project is a Promising program that uses in-home visitation and day care to deliver parent training and other family and child services. This intervention targets healthy, first-born infants of mothers with incomes below the poverty level who live in inner cities. The 30-month program includes weekly home visits (usually by a social worker), pediatric medical care, psychological services, and early education (day care) for children. Ten-year follow-up of families involved in the Yale Child Welfare Project shows that the program has pos itive effects on parent involvement in their children's education, academic achievement (less need for reme dial and supportive services), and antisocial behavior.
Striving Together to Achieve Rewarding Tomorrows, CASASTART, formerly known as the Children At Risk (CAR) program, targets at-risk youths age 11 to 13 who live in severely distressed neighbor hoods. The intervention has eight core components; each targeting a different context that affects the risk of violence: community-enhanced policing/enhanced enforcement, case management for youth and families, criminal/juvenile justice intervention, family services, after-school and summer activities, educational services, mentoring, and incentives for participation. Evaluations of CASASTART demonstrate that it has positive effects on avoidance of gateway drug use, violent crime, and drug sales and that these effects are sustained up to 1 year after participation.
The most comprehensive of these Promising mul ticontextual interventions is Families and Schools Together, or the FAST Track project. This interven tion combines several of the strategies identified in this chapter as effective: social skills training, parent training, home visitation, academic tutoring, and classroom behavior management techniques. The pro gram targets children identified as disruptive in kindergarten and aims to prevent severe, chronic con duct problems by increasing communication and strengthening bonds between the school, home, and child, thereby enhancing social, cognitive, and prob lem-solving skills and improving peer relationships. FAST Track has positive effects on several risk factors associated with youth violence, including academic achievement and parent-child relationships. Although initial evaluations did not show any effects of this program on children's antisocial behaviors, the long term follow-up studies now in progress should be able to determine whether FAST Track has a significant effect on this violence-related outcome.
Another comprehensive Promising intervention, The Incredible Years Series, is a series of curricula for parents, teachers, and children aimed at promoting social competence and preventing, reducing, and treat ing conduct problems in at-risk children age 3 to 8 . In each of these three curricula, trained facilitators use videotapes to encourage problem solving and discus sion.

# Academic Programs
Several educational approaches are effective at improv ing academic achievement, a weak but nevertheless important risk factor for late-onset youth violence (see Chapter 4). An effective secondary prevention strategy for improving academic performance is compensatory education, which targets students at risk of academic failure. Compensatory education strategies (such as cross-age or adult tutoring) that involve pulling stu dents out of their regular classes to receive extra assis tance in reading and math can improve long-term aca demic performance for all students, regardless of their achievement level. Moreover, when older students tutor younger students, both groups show academic gains. A meta-analysis of peer and cross-age tutoring of elemen tary and middle school students showed substantial effect sizes for academic achievement in both tutors and those tutored (Cohen et al., 1982). In more recent years, the compensatory education approach has been expanded to include schoolwide interventions.
Preventive Intervention is a 2-year, school-based behavioral reinforcement program that begins in grade 7 and targets students with low academic moti vation, family problems, or disciplinary problems. The intervention includes behavior monitoring and reinforcement in the classroom as well as enhanced communication (through regular classroom meetings and reports to parents) between teachers, students, and parents regarding behavior and attendance at school.
Educational assistance is one of three major com ponents of the Quantum Opportunities Program, a community-based intervention that targets adoles cents from families receiving public assistance. Students who participate in this program are assigned to a peer group and a caring adult and receive up to 250 hours of educational services to enhance academ ic skills; activities targeting personal development, life skills, career planning, and other areas; and serv ice opportunities in the community. The intervention begins at grade 9 and continues through high school.
Both of these programs have demonstrated posi tive effects on several aspects of academic achieve ment, and Preventive Intervention has been shown to reduce drug use and the risk of having a county court record 5 years after participation.

# Moral-Reasoning, Problem-Solving, Thinking Skills
As seen in some of the programs above, interventions that aim to improve youths' moral-reasoning, problem solving, and thinking skills are also effective approach es to reducing youth violence in high-risk populations. For instance, one moral-reasoning-based intervention implemented in "behavior-disordered" high school stu dents has demonstrated lasting positive effects by reducing police contacts and official school disciplinary actions (Arbuthnot & Gordon, 1986). Evidence of the effectiveness of social problem-solving interventions includes a study of children and young adolescents referred for treatment of antisocial behavior; these youths showed significantly lower aggression scores after treatment and lower rates of externalizing behav ior 1 year later (Kazdin et al., 1989).
The evidence supporting thinking skills approaches is similar, with particularly impressive results from two interventions: Lochman's Anger Coping Intervention and Rotheram's social skills training intervention. Lochman (Lochman, 1992;Lochman et al., 1984) reports large reductions in dis ruptive-aggressive behavior immediately after the program and reductions in substance use 3 years later in high-risk, aggressive boys in grades 4 through 6 . Rotheram's studies (1982) demonstrate improvements in academic achievement and in aggressive problem solving responses-both risk factors for violent behavior. Researchers speculate that one reason for the effectiveness of social skills interventions is that they are often more comprehensive in scope than other types of cognitive-behavioral approaches to pre venting youth violence and related outcomes.

# Ineffective Secondary Prevention Approaches
Whereas the research presented above demon strates that a large number of approaches and pro e m s can have significant, positive effects on youth violence and violence-related risk factors, several popular prevention approaches used in high-risk pop ulations have been shown to be ineffective. These include gun buyback programs, firearm training, and mandatory gun ownership.
Gun buyback programs, a particularly expen sive strategy, have consistently been shown to have no effect on gun violence, including firearm-related homicide and injury. This finding may appear coun terintuitive, given the fact that these programs do, in fact, take guns off the street. However, there is some evidence that most of the guns turned in are not func tional and that most persons turning in guns have other guns at home. Two less popular strategies, firearm training and mandatory gun ownership, have also demonstrated no significant effects on firearm-related crimes. These approaches were expected to deter gun violence by increasing the num ber of private citizens who were trained to use guns properly and who owned firearms for protection.
Two community-based strategies for preventing youth violence, redirecting youth behavior and shifting peer group norms, have also shown a lack of effect in reducing youth violence. In fact, because both approaches tend to group high-risk youths together, they can actually increase the cohesiveness of delinquent peer groups and facilitate deviancy training (Dishion et al., 1994(Dishion et al., , 1995. Programs that aim to redirect high-risk youth toward conventional activities involve recreational, enrichment, and leisure activities, including the popular Midnight Basketball program. In general, programs that focus on shifting peer group norms have attempted to turn youth gangs into benign clubs. Instead, these programs have had no effect or have actually increased gang-related delinquent behavior.

# Tertiary Prevention: Violent or Seriously Delinquent Youths
Each of the programs and strategies highlighted in this section is implemented on an indicated scale, that is, for young people who have already demon strated violent or seriously delinquent behavior. The best information on general strategies that are effec tive dr ineffective in reducing the risk of further vio lence among these youths comes from meta-analy ses. The most rigorous and most frequently cited meta-analyses of violence prevention programs are those conducted by Lipsey and colleagues and by Andrews and colleagues (Lipsey, 1992a(Lipsey, , 1992bLipsey & Wilson, 1998;Andrews, 1994;Andrews et al., 1990). This section draws largely on these analy ses, which include interventions targeting youths involved in any delinquent behavior and those involved in serious delinquent behavior. To enhance readability, the meta-analyses are cited here rather than throughout the text. Effect sizes are a stan dardized mean difference, corrected for small sam ple size and method effects. This measure reflects the average difference (expressed in standard devi ation units) between the program group and com parison groups in regard to violence, substance abuse, and risk factors.
Two major conclusions come from Lipsey's research. The first is that effective treatment can divert a significant proportion of delinquent and vio lent youths from future violence and crime. This finding contradicts the conclusions of scientists two decades ago who declared that nothing had been shown to prevent youth violence. The second major conclusion is that there is enormous variability in the effectiveness of different types of programs for seri ously delinquent youth. The most effective pro grams, on average, reduce the rate of subsequent offending by nearly half (46 percent), compared to controls, whereas the least effective programs actu ally increase the rate of subsequent offending by 18 percent, compared to controls. So, while some kinds of interventions substantially reduce youth violence and delinquency, others appear to be harmful (iatro genic), actually increasing involvement in these behaviors.

# Behavioral and Skill Development Interventions
Studies of male serious offenders demonstrate that treatment which includes a social perspective-taking/role-taking component can improve role-taking skills and reduce serious delinquent behavior for at - > .131 least 18 months after treatment (Chandler, 1993). This finding is consistent with results from the Lipsey (Table 5-1) and Andrews studies, which indicate that multimodal, behavioral, and skills-oriented inter ventions are more effective than counseling and other less-structured approaches (see also Gendreau & Ross, 1987). In fact, in most youth populations-uni versal, selected, or indicated-behavioral and skillsoriented strategies are among the most effective vio lence prevention approaches.

# Family Clinical Interventions
Although Lipsey reports only a small average effect size for reducing recidivism with family therapy (Table 5-1), the review literature indicates that specif ic strategies can be quite effective at preventing vio lence in delinquent youths and preventing further vio lence in already violent youths. One such approach is marital and family therapy by clinical staff. While marital and family therapy can include several differ ent strategies, a common thread is the focus on chang ing maladaptive or dysfunctional patterns of family interaction and communication, including negative parenting behaviors-all risk factors for youth vio lence. Marital and family therapy shows consistent, positive effects on family functioning, child behavior, family interactions, and delinquency (Tremblay & Craig, 1995). Long-term studies have demonstrated positive effects of family therapy by clinical staff last ing up to 9 years. Three Model tertiary youth violence prevention programs that use the family therapy approach are Functional Family Therapy, Multisystemic Therapy, and Multidimensional Treatment Foster Care. They are described below.
Functional Family Therapy (FFT) is actually a secondary and tertiary prevention program, since it targets youths 11 to 18 years old at risk of or already demonstrating delinquency, violence, substance use, conduct disorder, oppositional defiant disorder, or disruptive behavior disorder. FFT is a multistep, pha sic intervention that includes 8 to 30 hours of direct services for youths and their families, depending upon individual needs. The phases of the interven-    & Wilson, 1998, p. 318). t+ This calculation assumes a 50% recidivism rate in the absence of intervention.
tion include engagement (to reduce the risk of early dropout), motivation (to change maladaptive beliefs and behaviors), assessment (to clarify interpersonal behavior and relationships), behavior change (including skills training for youths and parents), and generalization (in which individualized casework is used to ensure that new skills are applied to func tional family needs).
These services are delivered in multiple settings by a wide range of interventionists, including supervised paraprofessionals, trained probation officers, mental health technicians, and mental health professionals with appropriate advanced degrees. The benefits of FFT include the effective treatment of conduct disor-0 -oppositional defiant disorder, disruptive behavior )T COPY AVAILABLE l 3 3 i 6
disorder, and alcohol and other drug abuse disorders; reductions in the need for more restrictive, costly serv ices and other social services; reductions in the inci dence of the original problem being addressed; and reductions in the proportion of youths who eventually enter the adult criminal justice system. In two trials, recidivism was found to be lower among participants than controls. Evidence of a diffusion effect was also found, with fewer siblings of participants acquiring a court record in the 2 to 3 years following treatment. Multisystemic Therapy (MST) is an intensive family-and community-based treatment that address es multiple determinants of antisocial behavior. This approach is implemented within a network of inter connected systems that includes one or more of the following contexts: individual, family, peer, school, and neighborhood. MST targets families with chil dren in the juvenile justice system who are violent, substance-abusing, or chronic offenders and at high risk of out-of-home placement. Four types of servic es are delivered through a home-based model: strate gic family therapy, structural family therapy, behav ioral parent training, and cognitive-behavioral thera py. While the intensity of services ultimately depends on individual youth and family needs, the average MST family receives 60 hours of direct services delivered over a period of 4 months. Program out comes in serious delinquents include reductions in long-term rates of rearrest, reductions in out-of-home placements, improvements in family functioning, and reductions in mental health problems among treated youths, compared to controls.
Multidimensional Treatment Foster Care is a multisystemic (multicontextual) clinical intervention that targets teenagers with histories of chronic and severe criminal behavior as an alternative to incarcera tion, group or residential treatment, or hospitalization. Meta-analyses conducted by Lipsey and others demon strate that community-based treatment is more success ful than residential treatment for this population of youths. Multidimensional Treatment Foster Care implementers recruit, train, and supervise foster fami lies to offer youths treatment and intensive supervision at home, in school, and in the community. The program also provides parent training and other services to the biological families of treated youths, helping to improve family relationships and reduce delinquency when youths return to their homes. Youths who partici pate in this program also receive behavior management and skill-focused therapy and a community liaison who coordinates contacts among case managers and others involved with the youths. Evaluations indicate that Multidimensional Treatment Foster Care can reduce the number of days of incarceration, overall arrest rates, drug use, and program dropout rates in treated youths versus controls during the first 1 2 months after com pleting treatment; it can also speed the placement of youths in less restrictive, community settings.

# Justice System Services
Justice system approaches to preventing youth vio lence can be effective when they focus on providing services rather than instituting greater penalties. One promising justice system approach is wraparound services, in which comprehensive services are tai lored to individual youths, as opposed to trying to fit youths into predetermined or inflexible programs. Evaluations of Wraparound Milwaukee have shown reductions in recidivism and arrests during the year following participation.
One juvenile justice system approach to prevent ing youth violence meets the standards described above for a Promising program: Intensive Protective Supervision Project. This intervention removes delin quent youths (status offenders) under the age of 16 from criminal justice institutions and provides them with proactive and extensive community supervision. This program has been shown to have greater deter rent effects on referrals to juvenile court than standard protective supervision does.

# Ineffective Tertiary Programs and Strategies
Several popular juvenile justice approaches to pre venting further criminal behavior in delinquent youths have been shown to be consistently ineffective: specifically, boot camps, residential programs, milieu treatment, behavioral token programs, and waivers to adult court.

# Boot Camps
Perhaps the most well known of these approaches, boot camps for delinquent youths are modeled after military basic training, with a primary focus on disci pline. Compared to traditional forms of incarceration, boot camps produced no significant effects on recidi vism in three out of four evaluations and trends toward increased recidivism in two. The fourth evalu ation showed significant harmful effects on youths, with a significant increase in recidivism.
Boot camps typically focus very narrowly on phys ical discipline, a highly specific personal skill, rather than a broader range of skills and competencies, such as those addressed by effective programs. Boot camps are also a setting in which youths are exposed to other delinquent youths, who can act as models and positive ly reinforce delinquent behavior (Dishion et al., 1994).

# Residential Programs
Residential programs, interventions that take place in psychiatric or correctional institutions, also show little promise of reducing subsequent crime and vio lence in delinquent youths. While some residential programs appear to have positive effects on youths as long as they remain in the institutional setting, research demonstrates consistently that these effects diminish once young people leave. Evaluations of two residential programs showed that participating youths were actually more likely to be rearrested and to report they had committed serious offenses during follow up. In both studies, the comparison group consisted of youths assigned to regular training schools.
Two general approaches that are popular in resi dential settings are milieu treatment and behavioral token programs. Both strategies aim to change the organizational structures of residential programs. The milieu treatment approach is characterized by resident involvement in decision making and day-to-day inter action for psychotherapeutic discussion. While this approach shows some positive effects when individual responsibility is stressed, the more common strategy of group decision making has shown no positive effect on recidivism after release. Moreover, Lipsey and Wilson's meta-analysis shows that milieu therapy is one of the least effective approaches to preventing recidivism in serious juvenile offenders (Table 5-1).
In behavioral token programs, youths are reward ed for conforming to rules, exhibiting prosocial behav ior, and not exhibiting antisocial or violent behavior. Like some other residential approaches, behavioral token programs can have positive effects on targeted behaviors while youths are institutionalized. However, when this strategy is used alone, any such effects dis appear when youths leave the program.

# Waivers to Adult Court
Another popular justice system approach to deterring youth violence, waivers to adult court, can have par ticularly harmful effects on delinquent youths. The idea behind this approach, "adult time for adult crime," was widely accepted into practice in the 1990s, when youth violence escalated dramatically. Evaluations of these programs suggest that they increase future crim inal behavior rather than deter it, as advocates of this approach had hoped. Moreover, placing youths in adult criminal institutions exposes them to harm. Results from a series of reports indicate that young people placed in adult correctional institutions, compared to those placed in institutions designed for youths, are eight times as likely to commit suicide, five times as likely to be sexually assaulted, twice as likely to be beaten by staff, and 50 percent as likely to be attacked with a weapon (Bishop, 2000;Bishop & Frazier, 2000;Fagan et al., 1989;Flaherty, 1980).

# Counseling
Several counseling, therapy, and social work approach es to treating delinquent youths have also been shown to be ineffective in the review literature, a finding that is consistent with the results of Lipsey's meta-analyses (Table 5-1). One "mainstay" (Tolan & Guerra, 1994, p. 15) of the juvenile justice system's toolkit against youth violence, social casework, combines individual psy chotherapy or counseling with close supervision of youths and coordination of social services. Even when implemented carefully and comprehensively, programs that use this approach have failed to demonstrate any positive effects on recidivism. In fact, one long-term follow-up of delinquent youths treated in this setting shows several significant negative effects, including increases in alcoholism, unemployment, marital diffi culties, and premature death (McCord, 1978).
Meta-analyses also demonstrate that individual counseling can be one of the least effective prevention approaches for delinquent youths. However, the effects of this strategy appear to depend largely on the popula tion. Though relatively ineffective for general delin quency and only marginally effective for institutional ized seriously delinquent youths, individual counseling emerged as one of the most effective intervention approaches for noninstitutionalized seriously delin quent youths in Lipsey's studies (Table 5-1). The rea son for this difference is unclear, but it illustrates the importance of program characteristics other than con tent, particularly the importance of matching the pro gram to the appropriate target population. A meta analysis by Andrews and colleagues (1990) confirms this finding, demonstrating that appropriate treatment can deter reoffending, whereas interventions that are poorly matched to the populations served can have no effect or a negative effect.

# Shock Programs
One tertiary youth violence prevention intervention meets the scientific criteria established above for Does Not Work: Scared Straight. Scared Straight is an example of a shock probation or parole program in which brief encounters with inmates describing the brutality of prison life or short-term incarceration in prisons or jails is expected to shock, or deter, youths from committing crimes. Numerous studies of Scared Straight have demonstrated that the program does not deter future criminal activities. In some studies, rear rest rates were similar between controls and youths who participated in Scared Straight. In others, youths exposed to Scared Straight actually had higher rates of rearrest than youths not involved in this intervention. Studies of other shock probation programs have shown similar effects. (For more information on Scared Straight and similar shock probation interventions, see Boudouris & Turnbull, 1985;Buckner & Chesney-Lind, 1983;Finckenauer, 1982;Lewis, 1983;Sherman et al" 1997;Vito, 1984;Vito & Allen, 1981.)

# C o s t -E f f e c t iv e n e s s
Violence costs the United States an estimated $425 billion in direct and indirect costs each year (Illinois Center for Violence Prevention, 1998). Of these costs, approximately $90 billion is spent on the criminal jus tice system, $65 billion on security, $5 billion on the treatment of victims, and $170 billion on lost produc tivity and quality of life. The annual costs to victims are approximately $178 billion (Illinois Center for Violence Prevention, 1998). The most logical way to reduce these costs is to prevent violence altogether. Preventing a single violent crime not only averts the costs of incarceration, it also prevents the short-and long-term costs to victims, including material losses and the costs associated with physical and psycholog ical trauma.
Despite these facts, policy in the United States continues to focus on get-tough laws and incarceration for serious violent criminals, as opposed to prevention and intervention (Greenwood, 1995). Federal spend ing on school-based crime, violence, and drug preven tion programs is quite modest, compared to spending on crime and drug control strategies such as policing and prison construction (Gottfredson et al., in press). Not only are preventive approaches more beneficial than get-tough laws, some prevention and intervention strategies cost less over the long run than mandatory sentences and other get-tough approaches.
In an effort to determine the cost-effectiveness of California's three-strikes-and-you're-out law, which mandates life sentences for repeat offenders, Greenwood (1995) compared that approach to the benefits and cost-effectiveness of a number of crime prevention strategies. He estimated that each serious crime-homicide, rape, robbery, assault, or residential burglary-prevented by the three-strikes law cost the criminal justice system in California an additional $16,000 over the amount spent prior to this legisla tion. Using this price as the standard for cost-effec tiveness, Greenwood calculated the costs per serious crime prevented of four prevention and intervention strategies: ( 1) early childhood intervention (perinatal home visitation continuing through the first 2 years, combined with 4 years of enriched day care programs) for high-risk families, (2 ) parent training for families with children who have shown aggressive behavior ("acted out") in school, (3) improved public school programs that target all youth, and (4) early interven tions for very young delinquents. The costs calculated for each of these interventions included only direct program costs, not such indirect benefits as the money saved by averting incarceration or preventing victim trauma and its medical and social consequences.
Table 5-2 shows the benefits of the various pre vention and intervention programs with respect to the number of serious crimes each can be expected to pre- Source: Greenwood, 1995.
1 All estimates are based on 1992 crime figures and 1990 population figures.
2 Crime prevention numbers for first 5 years include child abuse.
vent over the course of 30 years. The major disadvan tage of the prevention approach is clear-there is a time lag between implementation of programs and the appearance of effects. Because of this time lag, pro grams that are cost-effective in the long run do not appear so in the short run. In addition, long periods between an intervention and the high-risk period of a youth's life offer more opportunity for decay of a pro gram's effects (Greenwood et al., 1998). In the case of early childhood programs, it takes approximately 15 years before significant effects on youth violence can be appreciated, given the peak ages at which young people are involved in violence. Early intervention with delinquent youths that includes day treatment and home monitoring has a shorter lag time because the intervention is introduced later in life yet early in a violent career.
Of the four approaches listed in Table 5-2, the most cost-effective in the long run is parent training, which costs only $392 to implement per serious crime averted after the program has been in effect 30 years. This is less than one-fortieth the estimated cost of preventing serious crime under the three-strikes law. Day treatment and monitoring for delinquent youths are also more cost-effective than mandatory sentencing, costing less than one-sixth as much as the three-strikes approach.
The least cost-effective of the four are prenatal and early childhood intervention and school-based programs that target all students. However, early childhood interventions that include prenatal home visitation and enhanced day care can be expected to 5 These reductions in ch ild abuse were not considered in this analysis. 0 136 halve the incidence of child abuse among high-risk families (that is, low-income families headed by a sin gle mother).5 Moreover, early childhood intervention may improve educational achievement and reduce teen pregnancy rates. School-based programs have benefits other than prevention of violent crime, including higher educational achievement for all stu dents. In a later analysis, Greenwood et al. (1998) found that school-based prevention programs that tar geted disadvantaged youths specifically and included incentives (such as cash) for graduating from high school were almost 1 0 times as cost-effective as the three-strikes approach.
In general, Greenwood's findings suggest that interventions targeting problem youths-either chil dren who act out or delinquent youths-are more costeffective than interventions that target general popula tions of youths. In addition, they confirm that preven tion is truly more cost-effective in the long run than incarceration.
Costs aside, prevention may not have as great an effect on rates of violence as imposing longer manda tory sentences on repeat offenders. Other analyses demonstrate that the three-strikes law can reduce seri ous crime by 2 1 percent, whereas graduation incen tives only reduce it by approximately 15 percent, par ent training by 7 percent, early childhood intervention by 5 percent, and delinquent supervision by less than 2 percent (Greenwood et al., 1998). However, the four prevention and intervention strategies combined cost nearly $1.2 billion per year less to implement than the three-strikes strategy alone, and together they could prevent a substantial portion of the 80 percent of seri ous crimes that are not averted by mandatory sentenc ing (Greenwood et al., 1998). Graduation incentive programs could pay for themselves with the money they save by averting the eventual incarceration of many youths, and the other prevention and interven tion strategies could pay for up to 40 percent of their costs in the same manner.
Studies of two targeted early childhood intervention programs, the Perry Preschool and the Elmira, New York, Prenatal and Infancy Home Visitation by Nurses, indicate that these programs can actually save the gov ernment up to three times their cost when delinquency prevention and other benefits are considered (Karoly et al., 1998). It is noteworthy that although the cost-effec tiveness data in Table 5-2 were calculated using crime and population statistics for California, they have national implications with respect to the relative costs and benefits of violence prevention and incarceration.
Researchers at the Washington State Institute for Public Policy, who conducted a similar analysis (Aos et al., 1999), point out that the most effective programs are not always the most cost-effective. They note the importance of matching the intervention to the popula tion-a particular challenge for programmers, but one that has a critical effect on both the overall effective ness and the cost-effectiveness of an intervention.
The results of the Washington study are summa rized in Table 5-3. While this table includes only the programs and approaches discussed in this report, the Washington study actually included many more programs and strategies, including some targeting adult offenders. All cost estimates in Table 5-3 were calculated using the same methodology so that pro grams can be compared. Although most costs are cal culated as direct, per-participant program costs, the costs of Multidimensional Treatment Foster Care are calculated relative to regular group home costs, and the costs of intensive supervision programs and boot camps are calculated relative to regular court proba tion costs. (Thus, the negative program cost of boot camps means that these programs cost less to imple ment than regular court probation programs.) This

# E R I C
-verall approach may not be the same one used by other researchers to calculate program costs, result ing in inconsistencies between costs in this table and those projected by individual program designers .
Nevertheless, the Washington study offers some useful insights into the cost-effectiveness of youth violence prevention. Looking at the benefits to the criminal justice system alone (that is, benefits to the taxpayer), many early interventions and selected strategies come close to paying for themselves with the money they save; others actually achieve benefits that are greater than program costs. The Seattle Social Development Project, for instance, now saves $0.90 from reduced rates of crime for every tax dollar spent. Programs targeting at-risk or delinquent youths can be even more cost-effective. For example, taxpayers today can expect to save $14.07 in future criminal jus tice costs for every dollar spent on Multidimensional Treatment Foster Care.
The same trend holds when considering the bene fits of youth crime prevention to both the criminal jus tice system and crime victims (personal and property losses)-the largest economic returns are achieved with interventions targeted at juvenile offenders, who are at greatest risk of future offending. The Model programs in this group return $ 1 1 to $ 2 2 for every dol lar invested. However, even programs aimed at nonof fenders can achieve significant cost benefits when future savings to potential crime victims (due to a reduction in the number of victims) and the taxpayer are combined. According to the Washington study, society gains at least $0.50 over program costs for each dollar spent on the Perry Preschool Program, Prenatal and Infancy Home Visitation by Nurses, the Seattle Social Development Project, and Big Brothers Big Sisters of America.
In general, these analyses underestimate the bene fits of prevention programs because they fail to con sider many of the indirect benefits of preventing seri ous or violent offenses, such as increased work pro ductivity, increased taxes realized, reduced welfare assistance costs, and reduced victim medical costs.

# C o n c l u s io n s
Clearly, we are past the era in which some observers believed that "nothing works" to prevent youth vio lence. Numerous programs have demonstrated their effectiveness in reducing risk factors for serious vio lence. At the same time, there is a pressing need to eval uate more youth violence prevention programs. Of the hundreds of programs currently in use throughout the United States, only six met the criteria for a Model pro gram, and 21 met the criteria for a Promising program.
Of the 266 school-based program modules reviewed by Gottfredson et al. (in press), all of which were formally evaluated against a control or comparison group, only 1 0 percent received the highest score for scientific rigor (the experimental design standard used here). For most O I RJCbeST copy available violence, crime, and drug prevention' programs now being implemented, there is simply no evidence regard ing effectiveness. Although well-designed program evaluations are expensive and time-consuming, they are the only way to determine the effectiveness of exist ing youth violence prevention programs.
Nearly half of the most thoroughly evaluated strategies for preventing youth violence are ineffective, however, and a few are even harmful. It is in society's best interest to evaluate programs before exposing chil dren and adolescents to them-otherwise we run the risk of harming young people rather than helping them.
The most effective youth violence prevention programs are targeted appropriately, address several age-appropriate risk and protective factors in differ-

# G o i n g t o Sc a l e
While identifying best practices in youth violence pre vention is critical to reducing the number of young people involved in and affected by violence, it is not the last step. The manner in which a program is imple mented can have an enormous impact on its effective ness-even the best programs are effective only when implemented with high quality and fidelity to the pro gram's design. In other words, using an effective strat egy is only part of what is required to achieve effec tive results. Details of program delivery, including characteristics of the youths receiving the interven tion, the setting in which they are treated, and the intensity or duration of the intervention, play impor tant roles in determining effectiveness. Programs must be delivered with design fidelity, to a specific popula tion of youths, within a specific context, and for a spe cific period of time.
Unfortunately, very little is known about how to preserve a prevention program's positive effects when it is implemented on a wide-scale or national level. What research has been conducted indicates that effective implementation is at least as important to a program's success as the characteristics and content of the program itself (Petersilia, 1990;Lipsey, 1992aLipsey, , 1992b. $tudies of program implementation consis tently find that effectiveness depends on the following principles, according to a review by Petersilia (1990, p. 130):
- The project addresses a pressing local problem.
- The project has clearly articulated goals that reflect the needs and desires of the "customer."
- The project has a receptive environment in both the parent organization and the larger system.
- The organization has a leader who is committed to the objectives, values, and implications of the proj ect and who can devise practical strategies to moti vate and effect change.
- The project has a director who shares the leader's ideas and values and uses them to guide the imple mentation process and ongoing operation of the project.
- Practitioners make the project their own rather than being coerced into it; that is, they buy into it, partici pate in its development, and have incentives to maintain its integrity during the process of change.
- The project has clear lines of authority: There is no ambiguity as to who is in charge.
- The change and its implementation are not complex and sweeping.
- The organization has secure administrators, low staff turnover, and plentiful resources. Gendreau et al. (1999) organize these same prin ciples into four categories: general organizational fac tors, program factors, change agent factors, and staffing activities. While they acknowledge the impor tance of a program's characteristics, such as its theo retical basis, they also stress that positive change and success are dependent on much more than the specif ic characteristics of a prevention program or interven tion. Characteristics of the implementer, the environ ment in which the program is implemented, and even the target population have a significant influence on overall program effects.
Both the Petersilia and Gendreau et al. studies dis cuss characteristics of effective implementation with in a correctional setting. The Centers for Disease Control and Prevention's (CDC) Best Practices of Youth Violence Prevention (Thornton et al., 2000) and a recent review by Gottfredson et al. (2000) suggest that many of the same characteristics help determine the success of violence and delinquency prevention programs. In particular, the CDC study highlights the importance of training, monitoring, and supporting the staff who implement a program on the local level. An appropriate match between staff and the target population can also contribute to program success, particularly in parent-and family-based programs. Staff must be committed to the program, experienced with the general strategy being used, knowledgeable about the target community, and capable of managing group dynamics and overcoming resistance. Likewise, as noted by Petersilia, maintaining community involvement is a key element of program success. Finally, linking a youth violence prevention program to existing strategies and support agencies in the com munity or school can contribute to success (Thornton et al., 2 0 0 0 ).
A similar group of implementation characteris tics affects the success of school-based delinquency prevention programs, according to Gottfredson and colleagues (2000). In a study of more than 1,200 schools throughout the United States, they found that extensive, high-quality training and supervision, as well as support for the program from the principal of the school, are key elements of success. Schools also appear to have greater success with standardized materials and methods, as well as programs that can be incorporated into the regular school program. Consistent with Petersilia's principles, local buy-in and initiation of school-based delinquency preven tion are important predictors of program success. Multiple sources of information, including the use of an expert to assist with training and implementation, also help to ensure positive results. Improvements in any or all of these factors should improve the quali ty of the overall prevention program-and its effects on youths.
The CDC recommends monitoring the progress and quality of program implementation on a local level. This step can be particularly important when implementing Model programs. The proven effective ness of these programs in multiple, long-term studies makes them suitable for implementation on a wide, or even national, scale, but even Model programs are successful only when implemented with fidelity. While it is not always necessary to conduct expensive outcome evaluations of Model programs, given their demonstrated positive effects and ongoing national evaluations, it is critical to monitor the quality of implementation on the local level.
Scientific research has established the effective ness of a number of prevention programs, and evalu ation studies are sure to identify more in the near future. Although the studies cited above offer valu able guidance, more research is needed on how to implement youth violence prevention programs with fidelity on a national scale, how to monitor program fidelity on this scale, and how to increase community and agency capacity for implementing these pro grams. In addition, large-scale program dissemina tion will affect the overall benefits of individual youth violence prevention programs. Addressing these issues will require a major investment of time and resources, but it is the essential next step in the continuing effort to find effective solutions to the problem of youth violence.  Thornton et al., 2000. 4. Developmental Research and Program s, Inc., 2000. 5. Howell, 1995. The 1995 O J JD P report does not include the full complement of the office's recommendations regarding youth violence prevention. Sin ce 1995, the group has released several sm aller publications in which it specifically recommends other prevention strategies identified as effective in this report.  - Evidence of effectiveness: Evaluations performed at the end of the 9th grade show that STEP students have fewer school absences, higher grade-point averages, more positive feelings about school, and a better self concept than controls. In long-term studies, STEP stu dents had lower dropout rates than controls (2 1 per cent versus 43 percent), higher grades, and fewer absences. In a replication of the program in middle and junior high schools, both STEP and control stu dents showed increases in substance use, delinquent acts, and depression, and decreases in academic per formance and self-confidence. However, these changes were significandy smaller among STEP stu dents than controls. Students who participated in STEP also had lower dropout rates than controls. Replication in students with lower risk profiles 1 year after participation in STEP confirmed these findings, showing lower rates of delinquency and higher self esteem, academic performance, and school attendance than controls. This program has not been evaluated in small or high-achieving schools. In past studies, the program has worked best in large schools. The major limitation to the evaluation research on this program is that the first study lacked pretest measures; howev er, the researchers reported no differences between treated students and controls with respect to atten dance and grades at baseline.
- For further information:   - Evidence of effectiveness: In a multi site, random ized evaluation, a follow-up through the expected time of graduation showed that treated youths were significantly less likely than controls to be arrested (0.17 versus 0.58 arrests per person), were more likely to graduate (63 versus 42 percent), were more likely to attend postsecondary schools (42 versus 16 percent), were less likely to be dropouts, were more likely to receive an honor or award, were less likely to become teen parents, and were more likely to be involved in community service, be hopeful about the future, and consider their lives a success. Follow-up for 2 years after graduation revealed per sistent, positive program effects.
- For further information:  (1989)(1990)(1991)(1992)(1993). Waltham, MA: Brandeis University Heller Graduate School Center for Human Resources.

# 4J
Chapter 6 A V ision for the Future I n the late 1990s, people in the United States were stunned by a series of tragic shootings at schools that were planned and carried out by youths. These shocking, widely reported events prompted the prepa ration of this Surgeon General's report on youth vio lence. Yet these shootings were not characteristic of youth violence nationally. Moreover, at the time of the shootings, youth violence in the United States appeared to be on a downward trend.
Serious youth violence-that is, physical assault by a child or adolescent that carries a significant risk of injuring or killing another person-began to emerge as a social and public health problem of siz able proportions in the 1980s. Arrests of youths for index crimes (robbery, aggravated assault, rape, and homicide) peaked in 1993 after a decade of climbing rapidly, leading some observers to express doubt that anything could be done to halt the epidemic of youth violence. By 1999, after 6 years of sustained decline nationwide, arrests of youths for robbery, rape, and homicide began to resemble the pre-epidemic arrest rates of 1983. A striking exception to this trend was arrests for aggravated assault, which remained 70 per cent above 1983 rates.
While arrest records and victimization reports indicated that youth violence was generally declining, other sources of information presented a different pic ture. In approaching youth violence as a public health problem, this report has looked beyond arrest and other criminal justice records to several national sur veys in which high school-age youths report in confi dence on their violent behavior. These self-reports reveal that the propensity for and actual involvement of youths in serious violence have not declined with arrest rates. Rather, they have remained at the peak rates of 1993, a troublesome finding. In January 2001, as this report goes to press, the first indications of a long-awaited downturn in self-reported violent behav ior are being countered by signs from the FBI's Uniform Crime Reports database that the decline in arrests of youths for violent crimes has bottomed out and, for some index crimes, has begun to climb again.
Clearly, the dynamics and magnitude of youth violence remain fluid and complex. Nevertheless, research in the past several decades has developed a wealth of information about the causes of youth vio lence and how to prevent it. Numerous studies have identified and examined specific risk factors for vio lence-the personal and environmental features of young people's lives that increase the statistical prob ability of their engaging in violent behaviors. Research also has begun to identify protective factors that appear to buffer the effects of risk factors. While this information has been accumulating, researchers, youth service practitioners, and others have been designing, implementing, and evaluating a variety of programs and strategies to reduce or prevent the occurrence of youth violence. The best of these inter ventions target populations of young people identified as being particularly at risk of becoming involved in a violent lifestyle.
Many effective intervention programs exist to reduce and prevent youth violence. The United States is well past the point where anyone can claim that "nothing works" to prevent youth violence or to mod ify the destructive life courses of youths who are either engaged in or appear to be headed for lifestyles characterized by violence. At the same time, however, many purported youth violence prevention programs used today are untested, and some are known to be ineffective or even deleterious to a child or adoles cent's healthy, safe development.
The courses of action highlighted below are potential next steps. These are not formal policy rec ommendations. Instead, they represent a vision for the future built on information we possess today. They are intended for policy makers, service and treatment providers, people affiliated with the juvenile justice system, researchers, and most important, the people of the United States. This vision for the future is present ed with the hope that it will engage an expanding number of citizens in the challenge of redressing the problem of youth violence.

# C o n t in u e t o B u il d t h e Sc ie n c e Ba s e
Scientific research is an essential underpinning of the public health approach to the problem of youth vio lence. Years of extensive research have revealed the scope of the problem, and we are beginning to under stand how to intervene effectively to reduce and pre vent violence. Yet most violence prevention programs used in schools, communities, and the justice system today have not been subjected to systematic scientific evaluation, so their effectiveness-or lack of effec tiveness-is unknown. Given evidence that some well-intentioned prevention and intervention pro grams have proved to be harmful, it is imperative that all programs be scientifically evaluated. Research must also be prepared to address areas of emerging concern. One that has become increasingly clear is the need for studies to investigate intimate violence, or dating violence, among youths to identify patterns that predict continuation of such behaviors into adulthood and to design new types of interventions targeting this form of violent behavior. Another area of concern requiring research is the impact of violent interactive media, such as computer games, on serious violent behavior.
This Surgeon General's report is issued at a time of unprecedented scientific opportunity in numerous disciplines-developmental psychology, sociology, criminology, epidemiology, neuroscience, and many other fields. No single research specialty holds the key to understanding, treating, and preventing vio lence. Rather, they must work together. One of the greatest challenges to researchers today is finding new ways to use the tools, strategies, and insights from these diverse fields of research to reveal the many fac tors that may lead a young person toward-or protect a young person from-involvement in violence. A related need is to invest in cross-level research designs that will enable researchers to examine individual, family, and community factors simultaneously.
Research frequently examines questions and issues that crop up in the daily lives of millions of people-the relationship of media depictions of vio lence to violent behavior is a key example; the impact of strategies to discourage firearm use is another. Such familiarity often increases the likelihood that a person will hold strong opinions regarding the effect of television or popular music, or the presence and use of weapons, on violent behavior. Appropriately designed and conducted research offers a factual basis, rather than opinion, for proposing and debating social policy. It is therefore critical to devise ways of giving people with diverse interests (including par ents, teachers, and others) a voice in identifying urgent research questions and to inform them about the conclusions drawn from research.

# A c c e l e r a t e t h e D e c l in e in G u n U se b y Y o u t h s in V io l e n t En c o u n t e r s
The carrying and use of guns by youths in violent encounters have declined dramatically since 1993, the peak of the violence epidemic. To accelerate that decline, we must seek to understand more completely the reasons for it. Are youths' decisions not to carry or use guns in violent encounters related to any specific strategies put in place to discourage firearm use, or did the drop in firearm use result from other factors or conditions? Clearly, important questions remain about precisely what has happened in communities nationwide to reduce the frequency with which ado lescents carry guns. While some research has addressed these questions (Blumstein & Wallman, 2000), further studies are imperative-data document ing the continuing magnitude of violent behaviors suggest that a return to lethal violence is likely if ado lescents once again carry and use guns in violent encounters.

# Fa c il it a t e t h e En t r y o f Y o u t h s in t o Effe c t iv e I n t e r v e n t io n P r o g r a m s Ra t h e r T h a n I n c a r c e r a t in g T h e m
In the 1990s, faced with the epidemic of violence and largely unaware that research had found some vio lence prevention programs to be effective-as well as often buying into the "just desserts" philosophy-the only option some legislators saw was to lock up vio lent youths to protect society. New evidence makes a compelling case that intervention programs can be cost-effective and can reduce the likelihood that youths will become repeat offenders. Given this evi dence, it is in the country's interest to place as many violent youths as possible in these programs, thus cor recting the imbalance that now favors use of the crim inal justice system over effective intervention pro grams. Reclaiming youths from a violent lifestyle has clear advantages over warehousing them in prisons and training schools.
Effective programs are not available in many communities. Special efforts must be undertaken to increase awareness of these programs, provide techni cal assistance and information about them, and devise incentives for states and communities to invest in test ed programs. At present, states and communities are squandering substantial amounts of money on untest ed programs or programs known to be ineffective. Policy makers must be encouraged to focus existing resources on programs that work; evidence of effec tiveness might be required, for example, as a condi tion of receiving Federal or local funding. An informed public is also critical in building support for effective alternatives to incarceration.

# D is s e m in a t e M o d e l Pr o g r a m s w it h I n c e n t iv e s T h a t W il l En s u r e F id e l it y t o O r ig in a l P r o g r a m D e s ig n W h e n T a k e n t o Sc a l e
Experience has shown repeatedly that intervention programs shown to be effective in their original sites do not yield uniform outcomes when replicated else where. Upon examination, program evaluators often find that subtle modifications have been introduced into the model program. Lack of a particular category of personnel in a given location, for example, may prompt a program director to substitute professionals or paraprofessionals without proper credentials. Faceto-face training sessions that initially encouraged interaction between a program originator and new staff may be supplanted by videotaped tutorials. The frequency of participants' contacts with a program may be lessened or program duration abbreviated.
Legislators, agency administrators, and program directors should be encouraged to identify incentives for ensuring that the integrity of a model program is not compromised when it is replicated.

# Pr o v id e T r a in in g a n d C e r t if ic a t io n Pr o g r a m s f o r I n t e r v e n t io n Pe r s o n n e l
The major challenge in implementing effective inter vention programs on a national scale is guaranteeing a well-trained staff that understands the intervention and its limitations. Staff must be adequately trained to deliver a particular intervention in the specific settings for which it was designed. Yet because the supply of appropriately trained individuals who are available to work in the variety of settings in which violence pre vention programs operate is limited, operational entropy often sets in. Establishing formal training pro grams and university certification programs will help ensure the quality of interventions.

# Im p r o v e P u b l ic A w a r e n e s s o f Ef f e c t iv e I n t e r v e n t io n s
Identifying specific youth violence interventions as effective in this report will probably stimulate demand for these programs. Youth advocacy organizations have an opportunity to educate citizens on how to interact effectively with their local educational and juvenile justice systems, with appropriate sectors of the elected government, and with private organiza tions involved in youth violence prevention.
Media campaigns and public service announce ments offer a means of increasing public awareness. News or documentary television programs featuring model programs have had a measurable impact both on the funding of the programs and on the volume of requests from sites throughout the country for infor-mation about the programs. The 1938 film Boys Town, with Spencer Tracy and Mickey Rooney, proved high ly beneficial to the reputation and funding opportuni ties available to Boys Town. Conceivably, featuring model youth violence prevention programs in popular films today could have an equivalent effect. The move to a public health focus on violence involves new players and new collaborative partnerships among criminologists, psychologists, psychiatrists, sociolo gists, neuroscientists, and others. Physicians and other general medical service providers have important roles to play, but they are not yet sufficiently involved. Preparation of the Surgeon General's report under scored the risks of disciplinary compartmentalization in the study of youth violence.
There is no common place where information needed by all parties interested in the problem of youth violence can be exchanged. A rich literature on research and services appears in the specialty journals of various disciplines, in professional newsletters, in the mass media, and increasingly on the World Wide Web. Lack of interaction between academic research centers and the community-based agencies responsible for imple menting youth violence prevention programs or provid ing medical services to victims (many of whom are also perpetrators) can result in significant costs.
A periodic, highly visible national summit that receives wide popular as well as specialized media coverage would offer a way of disseminating infor mation on new research findings, effective programs and strategies, best practices, and related information for diverse audiences.

# Im p r o v e Fe d e r a l , Sta t e , a n d L o c a l St r a t e g ie s f o r R e p o r t in g C r im e I n f o r m a t io n a n d V io l e n t D e a t h s
The proportion of law enforcement agencies nation wide that report arrests to the FBI's Uniform Crime Reports (UCR) program has been declining. In 1999, .
O participating agencies represented only 63 percent of the U.S. population. The accuracy of national esti mates would be enhanced if this reporting rate were improved. In addition to expanding the participation rate, opportunities for improvement might entail:
- Including arrest rates for all racial and ethnic groups. Hispanics in particular are not represented in systematic data collection systems.
- Encouraging law enforcement agencies to partici pate in the National Incident-Based Reporting System. Developed by the UCR, the incident-based reporting system provides a much richer data set for tracking violent crime than the aggregated data available in the current UCR. Another potentially useful, innovative data set is the National Violent Death Reporting System proposed by the Centers for Disease Control and Prevention. This data set would help in monitoring the magnitude and char acteristics of youth violence on a timely basis so that programmatic and policy responses can be more effectively planned and evaluated.
- Develop a standard set of questions for national self-report surveys (such as Monitoring the Future) that include serious violent offenses. Annual data from these surveys should be obtained from all adolescents age 11 through 17, not just high school seniors. At present, variation among surveys in the age of respondents, data obtained, and frequency of data collection severely limit any composite picture that might result. Data collection efforts must make use of the best methodology available and include follow-up questions on each reported violent event to determine weapon use, drug or alcohol involve ment at the time of the event, seriousness of injury, victim's relationship to offender, number of youths involved in the attack, and other details. Such data enable researchers to correct for the overreporting in the simple checklist used in most surveys.

# C o n c l u s io n
Youth Violence: A Report of the Surgeon General offers compelling testimony that the safety and well being of children and adolescents are issues of the utmost importance and urgency to individuals and lies organizations throughout the United States. The report has drawn on the expertise of countless persons in diverse private organizations; in local, state, and Federal government agencies; in schools; and most important, in families-all of whom are dedicating immense energy and caring to countering the most common threat to the lives of young Americans.
Thanks to these efforts and to the insights and actions of young people themselves, it is clear today that youth violence is not an intractable problem; rather, it is a behavior that we can understand, treat, and pre vent. This final chapter has offered courses of action intended to help inform the decisions that we must make as we strive to ensure that every child has the opportunity to grow and mature safely, healthily, and happily.
R e f e r e n c e Blumstein, A., & Wallman, J. (2000).. The crime drop in America. Cambridge, United Kingdom: Cambridge University Press.

# G lossary
Absolute deterrent effects. Effects that are demon strated when an intervention produces better out comes compared to no treatment.

# Age of onset (of serious violence).
The age at which an individual reports his or her first act of serious violence.
Age-specific prevalence. The proportion of youths at any given age who report having committed at least one serious violent act in the past year.

# Aggravated assault.
An unlawful attack by one per son upon another wherein the offender uses a weapon or displays it in a threatening manner, or the victim suffers obvious severe or aggravated bodily injury involving apparent broken bones, loss of teeth, possible internal injury, severe laceration, or loss of consciousness. Along with homicide, rob bery, and rape, one of the four violent crimes cov ered in this report.*

# Aggression (aggressive behavior).
Behavior, physical or verbal, that is intended to harm another person.

# Antisocial attitudes.
Favorable attitudes toward vio lence, dishonesty, and rule breaking with hostility toward authority.

# Antisocial behaviors.
Problem behaviors that range from relatively minor acts such as lying, stealing, truancy, disobedience, and temper tantrums to seri ous nonviolent or violent behavior such as burglary or aggravated assault.

# Attention-deficit/hyperactivity disorder (ADHD).
A cognitive disorder characterized by restlessness, excessive activity, and difficulty paying attention.

# Career length.
Variously defined as the number of years of active offending; or the maximum number of consecutive years of offending; or the span between the first and last year during which a youth meets the criteria for a serious violent offender.

# Case study research.
A type of study design involv ing multiple observations of a single individual over time.

# Chronic offenders.
Variously defined by some mini mum number of offenses; for example, youths with three or more serious violent offenses per year.

# Contagion effect (of violence).
Unproved notion that seeing or hearing about violence in news coverage encourages violent or aggressive behavior.

# Control group.
A group that receives standard care or no intervention in a research study, compared to the experimental, treatment, or intervention group.

# Co-occurrence (of problem behaviors).
The simul taneous display of violence and other problem behaviors (e.g., substance use, property crimes, gun ownership). Although these behaviors occur togeth er, it cannot be assumed that one behavior causes another.
Conduct disorder. Childhood disorder marked by persistent acts of aggressive or antisocial behavior.
Cross-sectional research. A type of study design, fre quently used in public opinion polls, surveys, and epidemiological research. It involves a single con tact with participants for data collection at a given point in time and thus does not permit researchers to estimate individual-level change, development, or predictive effects of a given risk or protective factor on later violent behavior.
Cumulative prevalence (lifetime prevalence or ever-prevalence). The proportion of youths at any particular age who have ever committed a serious violent offense.
Delinquent (antisocial) lifestyle. A pattern of con sciously chosen and sustained behaviors that include antisocial or illegal acts, typically involving property crimes, substance use, gun ownership, and promiscuity.
Deterrent effects (absolute). See Absolute deter rent effects.

# Deterrent effects (marginal).
See Marginal deter rent effects.

# Developmental perspective (on youth violence
). An approach to understanding youth violence that con siders the complex interaction of individuals with their environment at particular times in their lives; this approach recognizes that patterns of behavior change over the life course. Early-onset trajectory. A pattern of violent behavior that emerges before adolescence, defined in this report as about age 13. In this pathway, problem behaviors in childhood gradually escalate over time to more violent ones, culminating in serious vio lence before adolescence. This pattern is less preva lent than the late-onset trajectory and is character ized by higher offending rates, greater seriousness of adolescent offenses, and greater persistence of violence from adolescence into adulthood.
Effect size. The predictive power of an individual or general type of risk or protective factor; or the size of the deterrent effect of an intervention compared to no treatment or a standard treatment. The meas ure used for risk factor effect sizes in this report is a simple correlation between two variables. For pro gram effectiveness, the effect size measure is the average difference (standardized) between the treat ment and control group means on the selected recidivism measure.

# Effectiveness trials.
Research that tests for benefits to participants in a natural or applied setting.

# Efficacy trials.
Research that tests for benefits to par ticipants in a controlled or experimental setting.
Epidemiology. Study of the factors influencing the incidence, frequency, and distribution of healthrelated events in the population; identifying appro priate risk and protective factors for prevention and intervention programs.

# Experimental research.
A type of study design involving comparison of a group that receives an intervention (experimental or treatment group) and a group that receives standard care or no interven tion (control group) in which participants are ran domly assigned to one of these groups. This study design permits researchers to assess cause-andeffect relationships and can be used to determine intervention effectiveness.

# Externalizing symptoms.
A behavioral pattern charac terized by the acting out of psychological problems.
Hazard rate. The proportion of individuals who initi ate a given behavior (e.g., serious violence) at a given age.
Homicide. The willful (nonnegligent) killing of one human being by another; along with robbery, aggra vated assault, and rape, one of the four violent crimes covered in this report.*

# Iatrogenic.
In the context of youth violence, interven tions that are harmful or actually increase involve ment in violence.
Incident rate. The number of self-reported violent acts within a given-sized population, a measure of the volume of violence; as used in this report, the number of violent acts per 1,000 young people. o Public health approach. A practical, goal-oriented, and community-based approach to promoting and sustaining health. This approach seeks to identify risk and protective factors, determine when in the life course they typically occur and how they operate, and enable researchers to design preventive programs that are effective in reducing risk and promoting protec tion.

# Intervention.
Quasi-experimental research. A type of study design with experimental and control groups but without random assignment to these groups. Groups are matched on selected characteristics, or differences are controlled in the analysis. The claim of group equivalence or comparability is not as strong with this design as in an experimental design.

# Rape (forcible rape).
The carnal knowledge of a per son, forcibly and/or against that person's will; or not forcibly or against the person's will where the vic tim is incapable of giving consent because of his or her temporary or permanent mental or physical incapacity (or because of his or her youth). Along with homicide, robbery, and aggravated assault, one of the four violent crimes covered in this report.*

# Reliability (of research instruments or measures).
The consistency of a measure; the measure yields the same result on different occasions or applica tions (when no real change has occurred).

# Replication.
Repeating an intervention or prevention program at multiple sites to determine if the results will be the same; establishes that a program can be effective at other sites when implemented by new teams under different conditions.

# Risk factor.
In the context of youth violence, personal characteristics or environmental conditions that increase the likelihood that a young person will become violent but that may not actually cause a per son to become violent. Risk factors are grouped into individual, family, school, peer group, and communi ty domains. The more risk factors a young person is exposed to, the greater the likelihood that he or she will become violent.

# Risk marker.
A personal characteristic or environ mental condition associated with known risk factors but having no causal relation to violence on its own.
Robbery. The taking or attempting to take anything of value from the care, custody, or control of a person or persons by force or threat of force or violence and/or putting the victim in fear. Along with homi cide, aggravated assault, and rape, one of the four violent crimes covered in this report.*
Sampling. The selection of persons to be studied in a research project.
Schizophrenia-spectrum disorders. Broad category of disorders that includes individuals with symptoms such as serious distortions of reality (including hal lucinations and delusions), withdrawal from social interaction, and disorganization and fragmentation of perception, thought, and emotion, for which other plausible explanations could be ruled out.

# Secondary prevention.
In the context of this report, strategies and programs that reduce the risk of vio lence among youths who display one or more risk factors for violence (high-risk youths).
Self-directed violence. Self-inflicted injury and sui cide; not the focus of this report.
Self-report studies. Research that asks people in con fidence to describe their own behavior. In the con text of youth violence, surveys that ask young peo ple in confidence about violent acts they have com mitted or have been victims of during a given peri od of time.

# Serious violent crime (serious violence or index crimes).
As defined in this report, aggravated assault, robbery, rape, and homicide. ous and nonserious offenses. These youths account for a major share of all criminal behavior by persons under age 18.

# Serious violent youths.

# Socially disorganized community.
A community characterized by high levels of poverty, unemploy ment, high turnover of residents, and a large pro portion of disrupted or single-parent families.
Socioeconomic status. In reference to youths, their parents' education, occupation, and income.
Statistical significance. The level of confidence with which one can conclude that a difference between two or more groups (generally a treatment and con trol group) is the result of the treatment delivered rather than the selection process or chance. A proba bility value of .05 is widely accepted as the threshold for statistical significance in the social and behav ioral sciences; a probability value below this thresh old (p < .05) indicates that a difference of this mag nitude could happen by chance less than 5 percent of the time.

# Superpredators.
A new breed of violent youths who commit more frequent and vicious violent crimes, without remorse, than in previous generations. Contrary to a recent myth, there is no evidence that this type of violent youths emerged in the 1990s.

# Surveillance.
A type of research that establishes the nature of a health problem, describes its incidence and prevalence trends, and monitors its magnitude over time. Public health specialists use this infor mation to determine appropriate prevention and intervention efforts.

# Sustained effects. Changes in individual competencies
and environmental conditions produced by effective programs that last at least a year beyond treatment or participation in the intervention.

# Tertiary prevention.
In the context of this report, strategies and programs that prevent further vio lence or the escalation of violence among youths already involved in violent behavior.

# Uniform Crime Reporting (UCR) program.
Operated by the FBI since the 1930s, the program monitors arrests made by law enforcement agencies across the United States and compiles annual arrest information.
Validity (of research instruments or measures). Wraparound services. An approach that is designed to tailor social services to the individual.  ,63,66,68 Aggression,reduction in,49,51,64,66,69,106,108,109,111,112,116,137,146,147,148 1, 5, 9, 11, 17, 18-26, 27, 29, 32-34, 43, 48, 49, 52, 153 , racial and ethnic, 18, 20-21, 27-30, 31, 34 at greatest risk of school homicide, 31

# Youth Risk Behavior Survey (YRBS

# N______________________ _ ______________

# BEST COPY AVAILABLE
Functional Family Therapy (FFT)
- Contact information: James F. Alexander, Ph.D. University of Utah Department of Psychology, SBS 502 Salt Lake City, UT 84121 (801) 581-6538
- Evidence of effectiveness: In multiple clinical tri als, FFT achieved significant reductions in the pro portion of youths who reoffended (60 percent of treated youths were arrested after the program ver sus 93 percent of controls in one study and 11 per cent versus 67 percent in another) and the frequen cy of offending up to 2.5 years after participation in the intervention. Diffusion effects on the siblings of target youths have also been observed, with signifi cantly fewer siblings of FFT youths than control youths having juvenile court records 2.5 to 3.5 years after the program.
- For further information: - . - Evidence of effectiveness: A randomized evalua tion of Multidimensional Treatment Foster Care compared to group care in boys only demonstrated the following results at a 1 2 -month follow-up: Treated boys spent significantly more days in their placements, were less likely to run away from their placements, and spent twice as many days living with their families or relatives. One year after leav ing treatment, treated boys had significantly larger decreases in arrest rates than controls, had signifi cantly fewer arrests overall, and were significantly more likely not to have been arrested at all during follow-up. Treated boys also reported significantly fewer criminal activities (general delinquency, index offenses, and felony assaults). In prior evalu-ations that included both boys and girls, Multidimensional Treatment Foster Care improved rates of program completion, reduced rates of incar ceration and number of days incarcerated during the first year after treatment, and resulted in a faster drop in rates of problem behavior for seriously impaired youths.
-F o r further information: - Eddy, J. M., & Chamberlain, P. (2000). Family management and deviant peer association as mediators of the impact of treatment condition on youth antisocial behavior. Journal o f Consulting and Clinical Psychology, 5, 857-863.
- Moore, K. J., Sprengelmeyer, P. G., & Chamberlain, P. (in press). Community-based treatment for adjudicated delinquents: The Oregon Social Learning Center's "Monitor" treatment foster care program. Residential Treatment for Children and Youth.
- . show that participation in MST can have significant positive effects on behavior problems (including conduct problems, anxiety-withdrawal, immaturity, and socialized aggression), family relations, and self-reported offenses immediately after treatment. Fifty-nine weeks after referral, seriously delinquent youth who participated in MST had slightly more than half as many arrests as controls (mean = 0.87 versus 1.52), spent an average of 73 fewer days incarcerated in justice system facilities, and showed reductions in aggression with peers. After 2.4 years, MST youths were half as likely as control youths to have been rearrested. In Columbia, Missouri, MST improved family relations and arrest rates, including arrests for violent and substance-related crimes, and demonstrated a dose-response effect, with program completers demonstrating significantly more bene fits than dropouts.
-For further information: delinquency initiation, improvements in family man agement practices and parent-child relationships, greater attachment and commitment to school, and less involvement with antisocial peers. Follow-up at age 18 shows that the Seattle Social Development Project significantly improves long-term attachment and commitment to school and school achievement and reduces rates of self-reported violent acts and heavy alcohol use. At follow-up, students who received the full intervention were also less likely than controls to be sexually active, to have had mul tiple sex partners, and to have been or have gotten someone pregnant (this difference was only mar ginally significant, at p = .057). Replications of this program have confirmed its benefits in both gen eral and high-risk populations of youths.
-F o r further information:
The Midwestern Prevention Project - For further information: - Evidence of effectiveness: No significant differ ences between treated and control boys were observed immediately after treatment, but 2 years later treated youths were involved in fewer fights, were half as likely to have serious school adjust ment problems, and were less likely to be involved in delinquent activities than those in the control group. Boys followed to age 12 (3 years after the intervention) had significantly lower rates of delin quency, fighting, serious difficulties in school, and placement in special-education classes, and they were rated as significantly more well adjusted in school than controls. Three years later, treated boys were less likely than untreated boys to report gang involvement, drunkenness, or drug use in the past year, delinquency, and having friends arrested by police. Because the effects of this intervention on girls are unknown, these benefits can be expected only when the intervention is implemented in boys.
-For further information:  (2000). Communities That Care prevention strategies: A research guide to what works. Seattle, WA.
Perry Preschool Program - For further information:
- Berrueta-Clement, J. R., Schweinhart, L. J., Barnett, W. S., Epstein, A. S., & Weikart, D. P. (1984). - For further information: - Evidence of effectiveness: The most dramatic effects of the program were demonstrated in a 1 0year follow-up evaluation that showed reduced juvenile delinquency and improved school func tioning. Children in the program also demonstrated more positive self-ratings, higher educational goals, and increased self-efficacy. Benefits to par ents included greater encouragement of their chil dren's success and increased family unity. The existing evaluation research on this program is lim ited by several factors: The program has not been replicated; there was relatively high attrition of families in the initial studies that may have led to a positive bias in the follow-up results; and allocation to treatment and control groups was not random ized. This program is no longer deliverable-that is, no technical assistance is available to those who wish to implement it.
- For further information: - For further information: - For further information:
Good Behavior Game - For more information: - Evidence of effectiveness: In nursery school and kindergarten students, I Can Problem Solve signifi cantly reduced impulsive and inhibited classroom behavior and improved problem-solving skills at posttest and 1 year. A second study demonstrated sustained improvements in classroom behavior and problem solving 3 to 4 years after the end of the pro gram. In 5th-and 6th-graders, the program increased the use of positive and prosocial behav iors and improved peer relationships and problem solving skills. In general, it appears that the program is more effective in high-risk students than in stu dents from the general population. Prior studies of this intervention did not use a randomized study design and were limited by high attrition.
- For further information:

# Evidence of effectiveness:
In a series of six ran domized trials, the parent program reduced conduct problems and improved parent-child relationships.
In two randomized studies, the teacher program reduced peer aggression in the classroom, increased positive interactions with teachers and peers, and enhanced school readiness. Two randomized studies of the child program demonstrated reductions in conduct problems at home and school and improve ments in problem solving with peers. Program effects have been shown to persist for at least one year after treatment.
- For further information:
- Developmental Research and Programs, Inc. (2000). Communities That Care prevention strategies: A research guide to what works. Seattle, WA.

# Linking the Interests of Families and Teachers (LIFT)
- - Evidence of effectiveness: In short-term evalua tions, LIFT decreased children's physical aggres sion on the playground (particularly children rated by their teachers as most aggressive at the start of the study), increased children's social skills, and decreased aversive behavior in mothers rated most aversive at baseline, relative to controls. Three years after participation in the program, lst-grade partici pants had fewer increases in attention-deficit disor der-related behaviors (inattentiveness, impulsivity, and hyperactivity) than controls. At follow-up, 5thgrade participants had fewer associations with delinquent peers, were less likely to initiate pat terned alcohol use, and were significantly less like ly than controls to have been arrested.
- For further information:
- - Evidence of effectiveness: Evaluations of this pro gram have demonstrated enhanced school achieve ment in grades 2 and 3; improved parenting skills at the end of the program, at (the child's) age 4, and in grades 2 and 3; and reduced aggressive behavior by children at ages 4 to 7 and 8 to 11. Unfortunately, the evaluations of these programs conducted to date have been limited by high attrition rates.
- For further information:
- Preventive Intervention - Evidence of effectiveness: Evaluations of this pro gram demonstrate both short-and long-term effec tiveness on violence-related risk factors, including higher grades and attendance at the end of the pro gram; significantly lower drug use, school-related problems, and unemployment after 1 year; signifi cantly fewer students with county court records at 5 years; and lower rates of reported criminal behavior at the 1.5 year follow-up (marginal significance, p < .075). Program effects on self-reported criminal behavior did not reach statistical significance, although the treatment and control groups did differ significantly with respect to the proportion of stu dents with a juvenile record.
- For further information: - Bry, B. H. (1982). Reducing the incidence of adolescent problems through preventive inter vention: One-and five-year follow-up. American Journal of Community Psychology, 10, 265-276.
- Bry, B. H., & George, F. E. (1980). The preven tive effects of early intervention on the atten dance and grades of urban adolescents. Professional Psychology, 11, 252-260.
- Bry, B. H., & George, F. E. (1979) - Evidence of effectiveness: Evaluations of this intervention have demonstrated that PATHS improves self-control, understanding and recogni tion of emotions, the ability to tolerate frustration, the use of effective conflict-resolution strategies, thinking and planning skills, and conduct problems, such as aggression. In students with special needs, PATHS has also been shown to significantly reduce symptoms of anxiety, depression, and sadness and to reduce conduct problems.
- For further information:
- Greenberg, M. T., Kusche, C., & Mihalic, S. (1998) - Thornton, T. N., Craft, C. A., Dahlberg, L. L., Lynch, B. S., & Baer, K. (2000). - Evidence of effectiveness: An evaluation conduct ed 10 years after participation in the program showed that youths enrolled in the Yale Child Welfare Project missed significantly fewer days of school, required significantly fewer remedial and supportive school services, and were rated signifi cantly less negative and more socially well adjusted by their teachers compared to controls. Some pro gram effects on academic achievement showed sig nificant diffusion effects on siblings. However, the sample in this study was small, with only 14 of the original 17 pairs of matched treatment and control youths available for evaluation at follow-up. In addition, this study used a quasi-experimental design. This program is no longer deliverable-that is, no technical assistance is available to those who wish to implement it.
- For further information: - Seitz, V., Rosenbaum, L. K., & Apfel, N. H. (1985). Effects of family support intervention: A ten-year follow-up. Child Development, 56, 376-391.
Late-onset trajectory. A pattern of violent behavior that emerges in adolescence, defined in this report as about age 13. This pattern is more prevalent than the early-onset trajectory and is characterized by a shorter period of involvement, lower frequency of offending, and a lower likelihood of continuing into adulthood. Individuals who are characterized by this pattern typically give few external signs in child hood that they will become violent offenders.

# Level of control.
Efforts to take into account other factors that might influence the data or responses from participants in a research study; contributes to the quality of a given study.

# Level of evidence.
The strength of the evidence amassed for any scientific fact or conclusion.

# Lifestyle.
A pattern of consciously chosen, observable behaviors that a person engages in on a consistent and regular basis.
Locally representative (probability) sample. In this report, the term representative sample is used to refer to a probability sample-a sample that is selected in such a way that its characteristics can be generalized to the population (e.g., city or county) from which it was drawn with a known degree of accuracy. The accuracy of generalizations from probability samples is given in the form of a confi dence interval. In this report, 95 percent confidence intervals (CIs) are reported, indicating an upper and lower bound for the population estimate that is accurate at least 95 percent of the time.
Longitudinal research. Used in etiological (causal) and developmental research, a type of study design involving multiple contacts with the same study par ticipants over time; allows researchers to estimate how well a given risk or protective factor predicts later violent behavior for individuals or groups.
Marginal deterrent effects. Effects that are demon strated when an intervention produces significantly better outcomes compared to another treatment; may underestimate the true effects of the interven tion compared to receiving no treatment at all.

# Maturation effect.
An effect associated with growing older or maturing, it may refer to changes in one's physical or social development. The term refers specifically to a sharp reduction in youth violence observed during the transition to adulthood, usually during the late teen years to age 20.
Mediating-effects analysis. An analysis that permits researchers to determine whether a change in the targeted risk or protective factor accounts for an observed change in violence.

# Meta-analysis.
A rigorous statistical method of com bining the results of several studies to obtain more reliable estimates of the effects of a general type of treatment or intervention; can be used to summarize program evaluation and draw overall conclusions about the strength and consistency of the influence, or effect size, that particular types of programs have on violence.

# Model program.
A prevention program that meets the highest scientific standard for effectiveness, as evi denced in published evaluations; has a significant, sustained preventive or deterrent effect and has been replicated in different communities or settings. It has been shown to work and can be expected to have a positive result in a wide range of community . settings.

# Monitoring the Future (MTF

# National Electronic Injury Surveillance System (NEISS).
Operated by the U.S. Consumer Product Safety Commission since 1992, the system monitors types of injuries treated in emergency departments, including those related to firearms.

# National Television Violence Survey (NTVS).
A recent content analysis of television programming examining its portrayal of violence. The study assessed a total of 2,500 hours of television pro gramming during the 1994 through 1997 viewing seasons. Physical aggressiveness. Relatively nonserious forms of violent behavior, often displayed in early child hood and continued into adolescence, including hit ting, biting, kicking, punching, or otherwise inten tionally hurting others.

# National Youth Survey (NYS
Population-based studies. Studies based on general population samples rather than selected or institu tional samples (e.g., prisoners, hospital patients, nursing home residents, expelled students). Findings O from these studies apply to general populations, whereas findings from studies of selected or institu tional samples apply specifically to persons in these settings or groups.
Post-traumatic stress disorder (PTSD). Disorder in which a stressful experience is traumatic and pro duces severe, recurring symptoms.
Prevalence rate. As used in this report, the proportion of youths involved in one or more violent behaviors during some specified time interval, for example, the past year, by age 18, or ever.

# Primary prevention (true prevention).
As defined in this report, strategies and programs that reduce the likelihood that youths will initiate violent behavior compared to youths in a control group; programs designed to target youths who have not yet become involved in violence or encountered specific risk fac tors for violence; identifies behavioral, environmen tal, and biological risk factors associated with vio lence and takes steps to educate individuals and com munities about and protect them from these risks.

# Probability sample.
A sample selected in such a way that its characteristics can be generalized to the pop ulation from which it was drawn with a known degree of accuracy. The level of accuracy for pro portions, means, and correlations is presented as a 95 percent confidence interval, which contains the true population value 95 percent of the time. See Locally representative sample.
Promising program. Prevention programs in this cat egory meet two of the scientific standards for effec tiveness; they do not meet all of the rigorous stan dards of Model programs, but they are recognized and encouraged with the caution that they be care fully evaluated.
Protective factor. As used in this report, personal characteristics or environmental conditions that reduce the potential harmful effect of a risk factor for violent behavior; characteristics that buffer or mod erate the effect of risk.