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|  | **Chapter 4:**Risk Factors for Youth Violence

Introduction to Risk and Protective Factors
- Risk Factors  Protective FactorsA Note on Sources
- Summary   Risk Factors in Childhood    - Risk Factors by Domain  Summary
Risk Factors in Adolescence
- Risk Factors by Domain  SummaryUnexpected Findings and Effects
Proposed Protective Factors in Childhood and Adolescence
A Note on Sources
- Proposed Protective Factors by Domain  Summary
Conclusions

References

Appendix 4-A: Lipsey and Derzon’s Classes of Risk Factors

Appendix 4-B: Violence in the Media and Its Effect on Youth Violence

Media Violence: Exposure and Content

Major Behavioral Effects of Media Violence
- Television and Film Violence  Experimental StudiesCross-Sectional Surveys
- Longitudinal Studies  Other StudiesViolence in Other Media
- Potential Moderators of Behavioral Effects   Summary of Major Empirical Research Findings  Preventive Efforts  Implications  References      Chapter 4Risk Factors for Youth Violence
Research has documented the magnitude of youth violence and the trends in that violenceover time. 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 simpleanswer to these questions, but scientists have identified a number of things that putchildren and adolescents at risk of violent behavior and some things that seem to protectthem from the effects of risk. 
INTRODUCTION TO RISK AND PROTECTIVE FACTORS
The concepts of risk and protection are integral to public health. A risk factor isanything that increases the probability that a person will suffer harm. A protectivefactor is something that decreases the potential harmful effect of a risk factor. In thecontext of this report, risk factors increase the probability that a young person willbecome violent, while protective factors buffer the young person against those risks. Thepublic health approach to youth violence involves identifying risk and protective factors,determining how they work, making the public aware of these findings, and designingprograms to prevent or stop the violence.

Risk factors for violence are not static. Their predictive value changes depending onwhen they occur in a young person's development, in what social context, and underwhat circumstances. Risk factors may be found in the individual, the environment, or theindividual'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 appearuntil adolescence. Some involve the family, others the neighborhood, the school, or thepeer group. Some become less important as a person matures, while others persistthroughout the life span. To complicate the picture even further, some factors mayconstitute risks during one stage of development but not another. Finally, the factorsthat predict the onset of violence are not necessarily the same as those that predict thecontinuation or cessation of violence. 

Violence prevention and intervention efforts hinge on identifying risk and protectivefactors and determining when in the course of development they emerge. To be effective,such efforts must be appropriate to a youth's stage of development. A program that iseffective in childhood may be ineffective in adolescence and vice versa. Moreover, therisk and protective factors targeted by violence prevention programs may be different fromthose targeted by intervention programs, which are designed to prevent the reoccurrence ofviolence.

This report groups risk and protective factors into five domains: individual, family,peer group, school, and community, which includes both the neighborhood and the largersociety (Box 4-1). Factors do not always fit neatly into these areas, however. Brokenhomes are classified as a family risk factor, but the presence of many such families in acommunity can contribute to social disorganization, an important community-level riskfactor (Bursik & Grasmick, 1993; Elliott et al., 1996; Sampson & Lauritsen, 1994).
Risk Factors
Risk factors are not necessarily causes. Researchers identify risk factors for youthviolence by tracking the development of children and adolescents over the first twodecades of life and measuring how frequently particular personal characteristics andsocial conditions at a given age are linked to violence at later stages of the lifecourse. Evidence for these characteristics and social conditions must go beyond simpleempirical relationships, however. To be considered risk factors, they must have both atheoretical rationale and a demonstrated ability to predict violence—essentialconditions for a causal relationship (Earls, 1994; Kraemer et al., 1997; Thornberry,1998). 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 theonset or rate of violence. 
Box 4-1: Early and late risk factors for violence at age 15 to 18 and proposed protective factors, by domain
                                                Box 4-1 (click to enlarge)

As used in this report, risk factors are personal characteristics or environmentalconditions that *predict* the onset, continuity, or escalation of violence.

The question of causality has practical implications for prevention efforts. Preventiondepends largely on risk factors being true causes of violence. In practical terms,research has amassed enough strong, consistent evidence for the risk factors discussed inthis report to provide a basis for prevention programs, even though a strictcause-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 sociallearning and biological processes. This means that violent youths who have violent parentsare far more likely to have modeled their behavior on their parents’ behavior—tohave learned violent behavior from them—than simply to have inherited it from them.Likewise, society’s differing expectations of boys and girls—expecting boys tobe more aggressive, for example—can result in learned behaviors that increase ordecrease the risk of violence.

The bulk of the research that has been done on risk factors identifies and measurestheir predictive value separately, without taking into account the influence of other riskfactors. More important than any individual factor, however, is the accumulation of riskfactors. Risk factors usually exist in clusters, not in isolation. Children who are abusedor neglected, for example, tend to be in poor families with single parents living indisadvantaged neighborhoods beset with violence, drug use, and crime. Studies of multiplerisk factors have found that they have independent, additive effects—that is, themore risk factors a child is exposed to, the greater the likelihood that he or she willbecome violent. One study, for example, has found that a 10-year-old exposed to 6 or morerisk factors is 10 times as likely to be violent by age 18 as a 10-year-old exposed toonly one factor (Herrenkohl et al., 2000).

Researchers have theorized that risk factors also interact with each other, but to datethey have found little evidence of interaction. What evidence does exist suggests thatinteractions between or among factors produce only small effects, but work in this area iscontinuing. To date, much more research has been done on risk factors than protectivefactors, but that picture, too, is changing.

***Developmental Progression to Violence***Scientific theory and research take two different approaches to how youth violencedevelops—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 ofrisk factors at different stages of the life course. Chapter 3 describes two developmentaltrajectories for the onset of violent behavior—one in which violence begins inchildhood (before puberty) and continues into adolescence, and one in which violencebegins in adolescence.

In contrast, this chapter considers the timing of risk factors. It identifies theindividual characteristics, experiences, and environmental conditions in childhood oradolescence that predict involvement in violent behavior in late adolescence—that is,age 15 to 18, the peak years of offending. Research shows that different risk factors mayemerge in these two developmental periods and that the same risk factors may havedifferent effect sizes, or predictive power, in these periods.

The timing of risk factors and the onset of violence are connected. Only risk factorsthat emerge in early childhood can logically account for violence that begins beforepuberty. However, these early risk factors may or may not be implicated in violence thatbegins in adolescence. In fact, studies show that many youths with late-onset violence didnot encounter the childhood risk factors responsible for early-onset violence. For theseyouths, risk factors for violence emerged in adolescence (Huizinga et al., 1995; Moffittet al., 1996; Patterson & Yoerger, 1997; Simons et al., 1994).

Table 4-1 lists early and late risk factors and estimates their effect sizes forviolence at age 15 to 18. It does not distinguish between youths who became violent beforepuberty and those who first became violent in adolescence; both groups are included amongyouths who were violent in late adolescence. However, the table does indicate thatdifferent risk factors emerge before puberty (age 6 to 11) and after puberty (age 12 to14) and that the same risk factors have different effect sizes in these periods. Thus, forexample, the table shows that substance use in childhood has a greater effect on violenceat age 15 to 18 than parental abuse or neglect does and that substance use in childhoodhas a greater effect on violence than substance use in early adolescence. (The table isdiscussed at greater length below, in A Note on Sources.)
Table 4-1. Effect sizes of early and late risk factors for violence* at age 15 to 18
Table 4-1 (click to enlarge)
The distinction between early and late risk factors is important. To be effective,prevention programs must address the risk factors that appear at a particular stage ofdevelopment. The observed clustering of risk factors in childhood and in adolescenceprovides clear targets for intervention during these stages of the life course.                                        
***Limitations of Risk Factors***Risk factors are powerful tools for identifying and locating populations andindividuals with a high potential for becoming violent, and they provide valuable targetsfor programs aimed at preventing or reducing violence. But there are important limitationsto 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 powerful 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 multiple risks yet avoid becoming involved    in violence (Garmezy, 1985; Rutter, 1985; Werner & Smith, 1982, 1992).
- Because public health research is based on observations and statistical probabilities in    large populations, risk factors can be used to predict violence in groups with particular    characteristics or environmental conditions but not in individuals.
- Given these two limitations, assessments designed to target individual youths for    intervention programs must be used with great care. Most individual youths identified by    existing risk factors for violence, even youths facing accumulated risks, never become    violent (Farrington, 1997; Huizinga et al., 1995; 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 born 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 reducing    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 factors 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 allyoung people. All children go through the same basic stages of human development—andprevention of youth violence is based on understanding when and how risk factors come intoplay at various stages of development. Moreover, there is some evidence that most riskfactors are equally valid predictors of delinquency and violence regardless of sex, race,or ethnicity (Rosay et al., 2000; Williams et al., 1999). Sophisticated studies thatidentify how cultural differences affect the interplay of the individual and his or hersurroundings will make possible more effective prevention efforts.
Protective Factors
There is some disagreement about exactly what protective factors are. They have beenviewed both as the absence of risk and as something conceptually distinct from risk(Guerra, 1998; Jessor et al., 1995; Reiss & Roth, 1993; Wasserman & Miller, 1998).The former view typically places risk and protective factors on the opposite ends of acontinuum. For example, good parent-child relations might be considered a protectivefactor because it is the opposite of poor parent-child relations, a known risk factor. Buta simple linear relationship of this sort (where the risk of violence decreases asparent-child relations improve) blurs the distinction between risk and protection, makingthem essentially the same thing.1

The view that protection is conceptually distinct from risk (the view used in thisreport) defines protective factors as characteristics or conditions that interact withrisk factors to reduce their influence on violent behavior (Garmezy, 1985; Rutter, 1985;Stattin & Magnusson, 1996). For example, low family socioeconomic status is a riskfactor for violence, and a warm, supportive relationship with a parent may be a protectivefactor. The warm relationship does not improve the child’s economic status, but itdoes buffer the child from some of the adverse effects of poverty. Protective factors mayor may not have a direct effect on violence (compare Jessor et al., 1995 and Stattin &Magnusson, 1996).

Interest in protective factors emerged from research in the field of developmental psychopathology. Investigators observed that children with exposure to multiple risk factors often escaped their impact. This led to a search for the characteristics or conditions 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 children 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 information 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 ofdevelopment, they may interact, and they may exert cumulative effects (Catalano et al.,1998; Furstenberg et al., 1999; Garmezy, 1985; Jessor et al., 1995; Rutter, 1979; Sameroffet al., 1993; Thornberry et al., 1995). Just as risk factors do not necessarily cause anindividual child or young person to become violent, protective factors do not guaranteethat an individual child or young person will not become violent. They reduce theprobability that groups of young people facing a risk factor or factors will becomeinvolved 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 extensivereview of research on risk factors for aggression and other behavior problems.

Table 4-1 is adapted from the tables presented in the Lipsey and Derzon andHawkins et al. meta-analyses. The risk factors in Table 4-1 predictfelonies—that is, violent and property crimes—at ages 15 to 18, the peak yearsof involvement.2 Entries in bold are effect sizes from the meta-analyses by Lipsey andDerzon, Hawkins et al., and Paik and Comstock for various classes of risk factors; otherentries are effect sizes reported in two or more longitudinal studies. (Risk classes aredescribed in Appendix 4–A and later sections of this chapter.) Some of the riskclasses in Table 4-1 include several separate risk factors. For example,psychological condition includes hyperactivity, daring, and attention 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 inconsistentdiscipline as a separate risk factor, although Lipsey and Derzon include it in the poorparent-child relations class. Academic failure, family conflict, and belonging to a gangare 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 multiplestudies, with those for risk classes typically involving more studies than those forseparate risk factors. The studies reviewed in Lipsey and Derzon, Paik and Comstock, andHawkins et al. are not cited here; however, other studies that were used to establish arisk 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 orviolent behavior, but most of the behaviors included are either nonphysical, nonviolentacts or relatively minor forms of physical aggression. Risk factors for antisocialbehavior may be quite different from those that predict violent behavior (robbery,aggravated assault, rape, and homicide). Since antisocial behavior does not present thepotential for serious injury or death that violence does, this report relies on studiesthat identify risk factors for serious offenses generally and violent behaviorspecifically, bearing in mind that the vast majority of serious offenders report havingbeen involved in violent offenses.
Summary
Risk and protective factors can be found in every area of a child or adolescent’slife, they exert different effects at different stages of development, and they gainstrength in numbers. The public health approach to the problem of youth violence seeks toidentify risk and protective factors, determine when in the life course they typicallyoccur and how they operate, and enable researchers to design preventive programs to be putin place at just the right time to be most effective.

This chapter describes what is known about individual, family, school, peer group, andcommunity risk and protective factors that exert their effects in childhood andadolescence. It describes the power of early risk factors, which come into play beforepuberty, and late risk factors, which exert their influence after puberty, to predict thelikelihood of youth violence.

**Footnotes**

1

If the relationship to violence is nonlinear, risk and protection may take on a different meaning.  However, the conditions and characteristics identified as protective factors by those using the absence-of-risk conceptualization rarely, if ever, involve a nonlinear relationship to violence.     

2

As noted in Chapter 3, most violent offenders commit many serious property offenses (such as burglary, auto theft, and larceny), and most youths involved in serious property offenses (FBI index offenses) are also involved in violent offenses.  The risk factors described here are based on longitudinal studies that use self-reports to predict violent offenses.  Several of the studies also include official arrest data and thus predict self-reported offenses, arrests for serious or violent offenses, or both.     

3

Effect sizes for risk factors not included in the meta-analyses reported by Lipsey and Derzon (1988), Hawkins et al. (1998c), and Parik and Comstock (1994) are weighted (by sample size) mean correlations.  The effect sizes in Parik and Comstock are unweighted mean correlations.
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