Sex Offender Treatment: Research Results Inconclusive About What Works to Reduce Recidivism
Published: 1996-06-21T00:00:00

Fast Facts:

Highlights:
section_title: Why GAO Did This Study
paragraphs: Pursuant to a congressional request, GAO reviewed research results on the effectiveness of sex offender treatment programs in reducing recidivism.
section_title: What GAO Found
paragraphs: GAO noted that: (1) all of the research studies reviewed provided qualitative and quantitative summaries of sex offender treatment programs; (2) nearly all of the studies identified limitations in evaluating treatment effectiveness; (3) there was no consensus as to which treatment reduces recidivism; (4) the cognitive-behavioral treatment approach works well in treating child molesters and exhibitionists, but treatment effectiveness depends on the type of offender and treatment setting; (5) researchers did not engage in comparison studies to measure recidivism rates because of the studies' inconsistent measurements; (6) the research reports lacked sufficient descriptive information on how program participants are selected and recidivism measured; and (7) definitive conclusions could not be drawn about deviant sexual behavior because certain methodological weaknesses have underscored inferences.

section_title: Letter
paragraphs: This report responds to your request that we review and synthesize the current state of research knowledge on ways to prevent sex crimes against children. We subsequently agreed with your staff to cover sex crimes against both children and adults and to issue two reports to you. This report describes and synthesizes reviews of the research literature on the effectiveness of treatment programs for sex offenders. Specifically, we describe the reviews, report their findings on the effectiveness of treatment in reducing recidivism, and report their assessments of the supportability of conclusions drawn from existing research studies.
The second report, which we plan to issue later this year, will synthesize reviews of the research literature on education programs designed to prevent sexual abuse. It will also review research literature on the likelihood of child victims becoming adult offenders and what may be done to prevent that.
subsections: section_title: Background
paragraphs: In 1993, the most recent year for which published Uniform Crime Reporting data were available, there were 142,520 arrests in the United States for forcible rape and other sexual offenses. Public alarm about sex crimes has prompted legislative activity at both the state and federal levels. Since 1994, 49 states have enacted laws requiring sex offenders to register their addresses with state or local law enforcement officials, and 30 states have adopted provisions for notifying citizens of the presence of a sex offender in their community. In December 1995, Public Law 104-71, the Sex Crimes Against Children Prevention Act of 1995, was passed. This act increased penalties against those who sexually exploit children either by engaging in certain conduct or via computer use, as well as those who transport children with the intent to engage in criminal sexual activity. In May 1996, the Violent Crime Control and Law Enforcement Act of 1994 was amended to require the release of relevant information to protect the public from sexually violent offenders who reside in their communities.
The act, Public Law 104-145, also known as “Megan’s Law,” requires community notification of the presence of convicted sex offenders.
A 1994 survey by the Safer Society, a resource and referral center for sex offender assessment and treatment, indicated that there were 710 sex offender programs in the United States that treated adult pedophiles, rapists, and other sexual offenders. This number represented a 139-percent increase in the number of treatment programs since 1986. Of these, 137 were residential treatment programs (90 being prison-based), and 573 were outpatient or community-based programs.
There are three general types of treatment approaches: the organic, biological, or physical approach includes surgical castration, hormonal/pharmacological treatment, and psychosurgery; the psychotherapeutic approach includes individual, group, and familial counseling; and the cognitive-behavioral approach covers a variety of cognitive and skills training methods and includes behavior control techniques.
Psychotherapeutic treatment was the primary approach to treating sex offenders before the 1960s. Today, cognitive-behavioral approaches predominate. According to the Safer Society’s 1994 survey, 77 percent of sex offender programs used the cognitive-behavioral approach, 9 percent used the psychotherapeutic approach, and 14 percent used other treatment models. No program reported using the organic model alone as the basis for treatment.
Conducting rigorous research on the effectiveness of sex offender treatment is difficult for methodological and ethical reasons. Methodological obstacles include difficulty in selecting a sample of offenders for treatment who are representative of all sex offenders, obtaining adequate comparison or control groups against which to compare offenders receiving treatment, determining how to deal with offenders who withdraw or are terminated from treatment, and determining what criteria to use for judging the success or failure of treatment and information sources to use in making this determination.According to Furby, Blackshaw, and Weinrott (1989), conditions are not often conducive to doing rigorous sex offender treatment research. Rather than designing study samples and data collection procedures to meet the information needs of their studies, evaluators are often forced by short time frames and inadequate funding into using samples and data sources that are readily available.
Ethical issues arise when researchers must decide which offenders should be admitted into the treatment program. If treatment is withheld from some eligible offenders, they may be precluded from receiving the benefits of a potentially therapeutic intervention. If treatment is provided to all offenders, then the treatment’s efficacy cannot be well-tested empirically, and scarce resources may be expended on an ineffective program. Comparing alternative treatment conditions is one way to resolve the ethical dilemma.
section_title: Scope and Methodology
paragraphs: We collected, reviewed, and analyzed information from 22 research reviews on sex offender treatment issued between 1977 and 1996. These reviews were identified through a multistep process that included contacting known experts in the sex offense research field, conducting computerized searches of several online databases, and screening hundreds of studies on sex offender treatment. We sent the list of reviews to seven experts in the field to confirm the comprehensiveness of our list of research reviews.
We used a data collection instrument to systematically collect information on treatment settings and types, offender types, recidivism measures, methodology issues, follow-up periods, and conclusions reached from these reviews. (See app. I for a more detailed description of our methodology.)
We sent a draft of this report to three of the experts previously consulted to ensure that we had presented the information about the reviews fairly and accurately. Their comments were incorporated where appropriate. We did not send a draft to any other agency or organization because we did not obtain information from such organizations for use in this study. We did our work between October 1995 and March 1996 in accordance with generally accepted government auditing standards.
section_title: Description of the Research Reviews
paragraphs: The 22 research reviews covered about 550 studies on sex offenders. Of these studies, 176 were cited in 2 or more reviews, and 26 were cited in 5 or more reviews. Given the widely varying levels of detail provided in the research reviews, we could not always determine whether reference was being made to a study of sex offender treatment or to other types of studies on sex offenders (e.g., recidivism studies on untreated offenders and studies attempting to identify sex offender characteristics). Therefore, we could not precisely determine the total number of studies on sex offender treatment covered in these research reviews. We also did not determine how many studies covered in the 22 research reviews were duplicative in terms of researchers publishing multiple articles based on the same set of data. At least 10 reviews were authored or coauthored by individuals affiliated with a sex offender treatment program. The earliest study included in a research review was published in 1944, the most recent in 1996.
Almost all of the research reviews provided narrative assessments of original research studies, with approximately one-half also providing a tabular summary of at least some of the studies covered. Only one review performed a meta-analysis, which is a statistical aggregation of the results from multiple studies to derive an overall quantitative estimate of the effectiveness of treatment.
Most research reviews did not restrict their coverage to a single type of treatment, treatment setting, or offender type. Two focused primarily on a specific treatment setting—one on prison-based treatment programs and the other on hospital-based programs. Nine focused primarily on cognitive-behavioral approaches, five on organic treatment, and one on psychotherapeutic treatment methods. Half of the reviews included studies on offenders who committed intrafamilial crimes, while others were not always clear whether the offense was intrafamilial or nonfamilial.
In assessing recidivism results, most research reviews considered whether findings were based on official (e.g., parole violation, rearrest, reconviction) or unofficial (e.g., self-report, report from family members) indicators of outcome. When official data sources were described in the research reviews, conviction for a new sex crime was the single most frequently cited recidivism measure. In many cases, however, the review did not specify whether the original study used arrest and/or conviction for a sex or nonsex crime as the recidivism measure. As indicated earlier, sometimes this was because the original study itself was unclear about how recidivism was measured.
section_title: Research Reviews Varied in Their Conclusions About Treatment Effectiveness
paragraphs: Some of the research reviews concluded that treated offenders had lower recidivism rates than untreated offenders. Others felt that the studies undertaken were so flawed that no firm conclusions could be drawn. Many reviewers seemed to be somewhere in between. They tended to conclude that, while some recent treatment approaches appeared promising, more rigorous research was needed to firmly establish their effectiveness. These reviewers asserted that the more rigorous research should employ larger and more representative samples of treated and untreated offenders, with longer follow-up periods and with better indicators of recidivism.
Eighteen of the 22 research reviews included some discussion of cognitive-behavioral programs, and 12 of the 18 concluded that such programs were at least somewhat effective. These types of programs typically involved satiation, aversion conditioning, covert sensitization, and relapse prevention techniques either used alone or, more often, in combination with one another. Reviewers who concluded that cognitive-behavioral programs were effective often emphasized different components as being the source of their efficacy and differed in terms of what types of offenders they were most effective in treating. One reviewer, for example, concluded that deviant sexual behavior could be reduced by techniques involving covert sensitization, aversion therapy, and a combination of the two. Another set of reviewers concluded that comprehensive cognitive/behavioral programs, particularly when administered to exhibitionists and molesters, held the greatest promise for effective sex offender treatment. The National Research Council reported in 1994 that anger management may be appropriate for dealing with violent individuals, but that “it has not been demonstrated that, in fact, such techniques can alter a long-term pattern of sexually aggressive behavior.”
Seventeen of the 22 research reviews discussed organic treatments, and 6 of the 17 concluded that there was some evidence of effectiveness. However, there was no consensus even among these reviewers about a particular drug being most effective, nor about the duration of positive effects from such interventions.
Fifteen of the 22 research reviews discussed psychotherapeutic approaches to treatment. None concluded that the various forms of counseling that characterize this approach were sufficient by themselves to substantially alter the behavior of sex offenders. However, a number of reviewers indicated that psychotherapy was useful in diminishing recidivism when used in conjunction with other treatments.
Only two reviews attempted to quantify the overall benefit of treatment programs. A 1990 report by the Canadian Solicitor General stated: “A reasonable conclusion . . . is that treatment can be effective in reducing recidivism from about 25% to 10-15%.” The only known and available meta-analysis, or statistical aggregation, of treatment studies to date concluded that “the net effect of the sexual offender treatment programs examined . . . is 8 fewer sexual offenders per 100” (Hall, 1995). Both of these reviews included a range of sex offender types, treatment settings, and programs. They did not identify any particular subgroup of sex offenders for whom treatment was more effective.
Most reviewers, even those who were quite positive about the promise of sex offender treatment programs, felt that more work was needed before firm conclusions could be reached. They cited the methodological limitations of studies as the major obstacle to drawing firm conclusions about treatment effectiveness. Even those reviewers who appeared to be among the most positive and optimistic (at least regarding cognitive/ behavioral programs) echoed the general sentiment that “there are no conclusive data available from completely methodologically sound research” (Marshall and Anderson, unpublished).
section_title: Research Reviews Identified Methodological Limitations in Evaluating Treatment Effectiveness
paragraphs: The research reviews found that conclusions about the effectiveness of treatment programs were impeded by methodological weaknesses in the implementation and reporting of the studies. The problems identified may be grouped into three broad categories: (1) limitations in the methodological design of studies, (2) limitations in the recidivism measures used, and (3) limitations in how the studies were reported.
subsections: section_title: Limitations in Study Design
paragraphs: Nearly all of the reviews identified weaknesses in the study design as a problem with sex offender treatment research. While numerous design problems were identified, two were most recurrent. Of the 22 reviews, 15 were critical of the absence of comparison or control groups, and 12 were critical of follow-up periods that were inadequate in duration. In addition, 5 were critical of the inconsistent duration of follow-up periods.
To meaningfully interpret recidivism results, it is important for an effectiveness study to use a comparison group that is similar on key characteristics to the treatment group. Using a comparison group helps answer such questions as (1) what would recidivism rates have been without treatment and (2) what factors, other than the treatment program alone, may have affected recidivism? For example, such studies may find that treatment volunteers, those with significant community ties, and/or older offenders may have lower recidivism rates, even without treatment, than other types of offenders. Without a comparable no-treatment group of offenders against which to benchmark the results of the treatment group, it is difficult to know how much of an impact, if any, the treatment program had on recidivism.
The reviews found that, in the absence of comparison groups, researchers sometimes compared the recidivism rates obtained in their study against those obtained in other studies. However, explanations other than treatment and study characteristics could have accounted for different recidivism rates in these studies. These include differences in sex offense reporting rates, apprehension levels, and prosecutorial policies across different jurisdictions and study periods.
Research has shown that sex crimes are underreported and that the longer the follow-up period, the more accurate the assessment of recidivism. One reviewer noted that “Recidivism rates are most meaningful if they cover at least a five-year period, postincarceration” (Becker, 1994), while another suggested that “studies that follow up offenders for periods of as short as 5 years or less may be producing substantial underestimates of true rates of recidivism” (Finkelhor, 1986). Although we cannot be precise about the average length of follow-up because the research reviews did not report it in a systematic fashion, it appears that many of the studies covered in the reviews involved follow-up periods of less than 5 years.
Not only can follow-up periods be too short to accurately measure recidivism rates, reviewers also found it difficult to compare the outcomes of different studies because the studies varied in the amount of time they tracked offenders after treatment and no statistical analyses were performed to account for the differences. Studies reported recidivism rates after 3 months, 1 year, 4 years, 15 years, etc. Follow-up periods even varied within a single study. Offenders were reportedly at risk for periods ranging from 1 month to 20 years in a single study. While a short follow-up period may not invalidate comparisons between similar treatment and control groups, the recidivism rate obtained for both groups is likely to be an underestimate of the true recidivism rate, because offenders are more likely to be reported and apprehended for their sex crimes in the long run than in the short run.
Many of the reviews identified other weaknesses in the research design of sex offender treatment studies. These weaknesses included selection bias (e.g., program participants were selected because they volunteered, so study results may not have been generalizable to nonvolunteers), the use of small study samples, and failure to consider attrition from treatment in determining how outcome data were analyzed.
An ongoing study of institutionalized sex offenders in California was cited by several research reviews and experts in the field as employing a research design that attempts to control for many of the methodological problems besetting other studies. (The design and preliminary findings from this evaluation are described in app. II.)
section_title: Limitations in Recidivism Measures Used
paragraphs: The validity of conclusions about treatment effectiveness is greatly affected by which data sources are used to measure outcome. Given that research has indicated that sex offenses are underreported, that a single data source is likely to be incomplete, and that some data sources are less reliable than others, the fewer and less reliable the data sources on which recidivism measures are based, the greater the likelihood that recidivism rates will be underestimated.
Nearly three-fourths of the research reviews pointed out the problem of studies relying on too few data sources to measure recidivism. The reviews criticized studies that relied solely on either official records or offender self-reports to determine whether program participants had reoffended. They stated that both official records and self-reports are likely to contain measurement error. For example, both arrest and conviction records are likely to yield underestimates of recidivism if sex offenses are underreported. Self-report recidivism information may be unreliable. Such limitations in data sources would not affect the scientific validity of comparing the recidivism rates of treated and untreated offenders since both groups would be affected equally. However, these limitations could affect the accuracy of the recidivism estimates. Consequently, it is advisable to use multiple data sources to overcome the weakness of each single data source.
The operational definition of recidivism also has a significant bearing on the results obtained from outcome studies. In some cases, recidivism was defined as a rearrest or conviction for a sex offense; in others, it was defined as rearrest or conviction for any offense. In still other cases, recidivism was defined only as a rearrest, or only as a reconviction, with the nature of the crime unspecified. There seemed to be little consensus among reviewers about what an optimal indicator of recidivism would be. As a result, it was difficult to determine whether, and by how much, sex offender treatment reduced recidivism.
section_title: Limitations in How Research Was Reported
paragraphs: Nearly half of the reviews indicated some type of limitation in how sex offender treatment studies were reported. The most frequently indicated limitations included inadequate descriptions of the treatment programs, failure to report the criteria used to select study participants, and inadequate descriptions of recidivism measures. In the absence of such information, it is exceedingly difficult to synthesize the state of knowledge of sex offender treatment research. For example, without knowing the contents of a program or how program participants were selected for it, the ability to replicate the study and determine whether results are generalizable is diminished. Without knowing precisely how recidivism was measured in a study renders comparisons between it and other studies meaningless.
section_title: Conclusions
paragraphs: A substantial number of studies have been done on sex offender treatment effectiveness, many of which were assessed in the research reviews described and synthesized in this report. The most optimistic reviews concluded that some treatment programs showed promise for reducing deviant sexual behavior. However, nearly all reported that definitive conclusions could not be drawn because methodological weaknesses in the research made inferences about what works uncertain. There was consensus that to demonstrate the effectiveness of sex offender treatment more and better research would be required.
Copies of this report will be made available to others upon request. The major contributors to this report are listed in appendix IV. Please call me at (202) 512-8777 if you have any questions.