Week 10 Discussion

Article

Sex Offender Recidivism Revisited: Review of Recent Meta-analyses on the Effects of Sex Offender Treatment

Bitna Kim 1 , Peter J. Benekos

2 , and Alida V. Merlo

1

Abstract The effectiveness of sex offender treatment programs continues to generate misinformation and disagreement. Some literature reviews conclude that treatment does not reduce recidivism while others suggest that specific types of treatment may warrant optimism. The principal purpose of this study is to update the most recent meta-analyses of sex offender treatments and to com- pare the findings with an earlier study that reviewed the meta-analytic studies published from 1995 to 2002. More importantly, this study examines effect sizes across different age populations and effect sizes across various sex offender treatments. Results of this review of meta-analyses suggest that sex offender treatments can be considered as ‘‘proven’’ or at least ‘‘promising,’’ while age of participants and intervention type may influence the success of treatment for sex offenders. The implications of these findings include achieving a broader understanding of intervention moderators, applying such interventions to juvenile and adult offenders, and outlining future areas of research.

Keywords offenders, sexual assault, recidivism, intervention

Introduction

The topic of sex offenders generally elicits fear and anxiety

from the public and contributes to punitive policies aimed at

harsh, exclusionary punishments. The perspective that commu-

nities need to be protected from sex offenders through incar-

ceration and surveillance often overshadows the prospects

that treatment can also provide public safety. In their study,

Kernsmith, Craun, and Foster (2009) found that citizen respon-

dents who reported higher levels of fear of sex offenders were

more supportive of registration requirements for sex offenders.

Levenson, Brannon, Fortney, and Baker (2007) also reported

that public perceptions of sex offenders reflect public anxiety

and support for community protection.

Although negative attitudes toward sex offenders are not

reflective of all countries, cultural differences and historical

context can account for less punitive public responses. For

example, McAlinden (2012) found that therapeutic interven-

tions for sex offenders were more prevalent in European coun-

tries than in England and Wales. She attributes this to a more

scientific and medical approach to sex offending across Europe

and less emphasis on ‘‘sexual abuse as a moral, legal, and social

problem’’ (p. 170). Nevertheless, the sex offender problem has

become more serious across Europe and policies reflect a shift

toward more punitive attitudes and sanctions (McAlinden,

2012). Not only in European countries but also in the United

States, one of the misgivings about how to respond to sex

offenders concerns the effectiveness of treatment.

In this article, the authors address the treatment issue by

updating the meta-meta-analytic study of Craig et al. (2003)

on sexual offender treatment. This study augments the original

work of Craig et al. by incorporating more recent meta-analytic

studies in the analysis. In this research, all salient meta-analytic

sex offender treatment studies from 1995 to 2010 were

included. The purpose of this study is to systematically review

what is known about the effectiveness of sex offender treat-

ments based on results of extant meta-analyses of different

types of treatment for sex offenders.

Furthermore, the study examines the issue of treatment spe-

cificity and which treatment strategies are effective for adult

versus juvenile offenders. Juvenile offenders who commit sex

offenses can evoke more alarm and fear among the public and

prosecutors because age is viewed as an aggravating character-

istic that can contribute to reoffending. When the prosecutors

emphasize public safety, this not only reinforces fears, but also

justifies more punitive rather than therapeutic responses.

Michels reports that prosecutors can take the position that

1 Department of Criminology, Indiana University of Pennsylvania, Indiana, PA,

USA 2 Criminal Justice Department, Mercyhurst University, Erie, PA, USA

Corresponding Author:

Bitna Kim, Department of Criminology, Indiana University of Pennsylvania,

Indiana, PA 15705, USA.

Email: [email protected]

TRAUMA, VIOLENCE, & ABUSE 2016, Vol. 17(1) 105-117 ª The Author(s) 2015 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/1524838014566719 tva.sagepub.com

juvenile sex offenders are the ‘‘worst of the worst’’ because they

are more prone to reoffending and ‘‘therefore too dangerous to

release’’ (2012, { 9). This demonizing of juvenile sex offenders reflects a concern that this population cannot be effectively

treated, that they are at greater risk of recidivism, and that they

present a threat to public safety. Although these views are gen-

erally inaccurate, they do impact public reaction and prosecutor-

ial responses (Chaffin, 2008; Letourneau & Miner, 2005).

This study assesses the effectiveness of sex offender treat-

ment programs and includes 11 meta-analytic studies, 6 of

which were included in the Craig et al. (2003) study and 5 of

which are more recent. Cohen’s d was reported to aid in the

interpretation of effect sizes. Definitions of small (d ¼ .20), medium (d ¼ .50), and large (d ¼ .80) effects were based on Cohen’s (1988) guide and based on effect sizes encountered

in the behavioral sciences (Cooper, 2010). These guides are

most appropriately employed ‘‘when no better basis for esti-

mating the effect size is available’’ (Cohen, 1988, p. 25).

Two other descriptors of research results related to program

evaluations that have recently received attention among some

social scientists are ‘‘proven’’ and ‘‘promising’’ (Cooper,

2010). Among different guides for magnitude labels of proven

and promising, the Promising Practices Network (PPN) is con-

sidered as credible by associating the terms such as proven and

promising with the solid evidence criteria (e.g., type of out-

comes affected, substantial effect size, statistical significance,

comparison groups, sample size, and availability of program

evaluation documentation (Cooper, 2010; PPN, 2007).

According to the PPN (2007), in order for a program to be

labeled proven, the associated evidence must meet the follow-

ing criteria: ‘‘(1) the program must directly affect one of the

indicators of interest; (2) at least one outcome is changed by

20%, d ¼ .25, or more; (3) at least one outcome with a substan- tial effect size is statistically significant at the 5% level; (4) the study design used a convincing comparison group to identify

program impacts, including studies that used random assign-

ment or some quasi-experimental designs; (5) the sample size

of the evaluation exceeds 30 in both the treatment and compar-

ison groups; and (6) the report is publicly available’’ (Cooper,

2010, p. 209). An intervention would be labeled promising if it

measured the outcomes of most interest and used rigorous

designs and revealed a smaller effect size (e.g., an associated

change in outcome of more than 1%) that PPN requires for a program to be considered proven (Cooper, 2010, p. 209). One

purpose of this study is to determine whether the current evi-

dence supports a conclusion that sex offender treatment is pro-

ven or promising. This study utilizes both Cohen’s (1988)

guide and the PPN (2007) guide to convey proven and promis-

ing findings of sex offender treatments.

Sex Offender Treatments

Cognitive Behavioral Therapy

The treatment foundation that is used in many sex offender pro-

grams is cognitive behavioral therapy (CBT) and relapse

prevention (Baker, 2012; Brandes & Cheung, 2009; Center

for Sex Offender Management, 2006; McGrath, Cumming,

Burchard, Zeoli, & Ellerby, 2009; Worling & Langton, 2012).

Based on their survey of 1,379 programs in the United States

and Canada, McGrath et al. (2009) reported that the cognitive

behavioral model was in the top three choices for most adult

and adolescent programs (86%) and relapse prevention was in the top two choices for 50% of the programs.

CBT combines two psychotherapies to address thoughts and

beliefs as well as behaviors and actions (Development Services

Group, Inc., 2009). The cognitive focus is on assumptions and

attitudes that contribute to dysfunctional thinking that rein-

forces patterns of unacceptable or inappropriate behaviors. The

behavioral component emphasizes actions and settings that

contribute to patterns of behavior. This problem-focused

approach helps sex offenders learn new skills and develop com-

petencies in maintaining appropriate behaviors. CBT confronts

rationalizations about behavior and provides skills to control

sexual impulses. Similarly, relapse prevention is also a cogni-

tive approach that helps sex offenders regulate their own beha-

viors by recognizing internal and external risks and learning to

manage their behaviors.

In his review of CBT, Greenwald (2009) described struc-

tured intervention strategies that improve interpersonal

problem-solving skills and facilitate more effective communi-

cation skills. By developing self-management skills that recog-

nize social cues and maladaptive behaviors, treatment provides

more constructive ways of thinking and understanding the con-

sequences of behavior. Corson (2010) also noted that social and

life skills training and cognitive restructuring are characteris-

tics of CBT. Essentially, treatment programs include various

strategies that focus on correcting thoughts, feelings, and beha-

viors that promote inappropriate behaviors and replacing them

with self-directed behavioral skills that maintain prosocial

beliefs and behaviors.

As previously noted, CBT presents strategies that are effec-

tive in cognitive restructuring that improve victim empathy and

complement relapse prevention (Craig, Browne, & Stringer,

2003; Hanson, Bourgon, Helmus, & Hodgson, 2009). Galla-

gher, Wilson, Hirschfield, Coggeshall, and MacKenzie

(1999) noted that cognitive behavioral treatment is not only

broadly supported in the literature, but also in their meta-

analytic study of 25 studies, in which they found that ‘‘ . . . cognitive behavioral programs are effective in reducing the

recidivism of treated offenders’’ (p. 27). In addition, Marshall

and McGuire (2003) found supporting evidence that treatment

of sex offenders is effective. In reporting that recidivism among

sexual offenders is lower than among other offenders, Mann,

Hanson, and Thornton (2010) observe that this contradicts

common beliefs.

CBT is also the most prevalent treatment approach for ado-

lescent sex offenders and has wide support. For example, in their

meta-analytic study, Reitzel and Carbonell (2006) found that

cognitive behavioral approaches were the most effective for

juvenile offenders. The cognitive behavioral treatment–relapse

prevention (CBT-RP) approach to treatment underscores

106 TRAUMA, VIOLENCE, & ABUSE 17(1)

changing ‘‘thoughts, behaviors, and arousal patterns of juvenile

sex offenders’’ (Fanniff & Becker, 2006, p. 273).

Generally, programs that use CBT-RP to work with adoles-

cent sex offenders motivate them to reject their thinking errors

and to identify situations and ideations that precipitate inap-

propriate behaviors. In addition, adolescents learn to recognize

the connection between their emotions and behaviors. (Bourke

& Donohue, 1996; Hall, 1995; Hunter & Santos, 1990; Lipsey,

2009; Marques, Wiederanders, Day, Nelson, & van Ommeren,

2005). Since juveniles are still maturing, developing, and

experimenting, there is an expectation that they are more

responsive to cognitive restructuring and skills development.

This is consistent with findings that juvenile sex offenders who

receive treatment have low rates of reoffending (Baker, 2012;

Center for Sex Offender Management, n.d.; Reitzel & Carbo-

nell, 2006).

Multisystemic Therapy

Another promising approach for treating sex offenders is multi-

systemic therapy (MST) (Borduin, Schaeffer, & Heiblum,

2009; Fanniff & Becker, 2006; Henggeler, 2012; Huey, Heng-

geler, Brondino, & Pickrel, 2000; MST Associates, n.d.). MST

was originally developed by Scott Henggeler as a family-based

treatment program for antisocial children and serious delin-

quent offenders. The emphasis of MST was on working with

families to improve monitoring, supervising, and disciplining

youth, and on reducing deviant peer affiliations (MST Services,

n.d.). MST has been adapted and has demonstrated effective-

ness in treating adolescent socialization issues and interperso-

nal relations (Crime Solutions, n.d.; Henggeler, 2012). The

intervention is provided at home or in the community and

focuses on interrupting the sexual assault cycle by working

with the offender and his family to develop a safety plan, by

empowering the family with skills and resources to more effec-

tively parent, and by targeting treatment toward individual

and family risk factors for sexual and nonsexual delinquency

(Fanniff & Becker, 2006; Henggeler, 2012).

Borduin et al. (2009) reported that juvenile sexual offenders

treated with MST had lower recidivism rates than offenders

receiving ‘‘usual’’ community services. Multiple randomized

controlled trials of MST provided to juvenile sex offenders

have found reductions in recidivism, problematic sexual beha-

vior, and out-of-home placements (Letourneau et al., 2009). In

their meta-analytic study, Walker, McGovern, Poey, and Otis

(2004, p. 289) found that MST appeared promising and they

recommended that future research on adolescent sexual offen-

der treatment ‘‘test the effectiveness of CBT against that of

multisystemic therapy.’’

Using their findings from a meta-analysis and distinguishing

between specialist and generalist sex offenders, Pullman and

Seto (2012) recommended both MST and CBT in order to

achieve more effective treatment outcomes. They concluded

that using MST and CBT to focus on sexual self-regulation

results in lower recidivism for specialist adolescent sex offen-

ders than using MST alone.

Additional Sex Offender Treatments

Sex offender therapy can also include medical interventions

that are either physical or chemical. Surgical procedures denote

mechanical castration, and chemical castration refers to hormo-

nal drugs such as antiandrogen, which are used to reduce sexual

arousal (Pray, 2002, p. 99). Gallagher et al. (1999) reported that

cognitive behavioral treatment (or other psychological treat-

ment) is sometimes used in conjunction with hormonal treat-

ment such as Depo-Provera, which reduces physiological

drive to engage in deviant behavior (Gallagher, Wilson,

Hirschfield, Coggeshall, & MacKenzie, 1999, p. 25).

In his study of hormonal treatments, Hall (1995) found that

effect sizes in studies that used a cognitive behavioral approach

were not significantly different from those that employed hor-

monal treatments. Hall performed a meta-analysis of 12 pri-

mary studies and found that both cognitive behavioral and

hormonal treatments were effective. However, the refusal and

discontinuation rates of hormonal treatment participants is con-

siderably higher compared to cognitive behavioral treatment

participants, and Hall suggests that this may indicate that cog-

nitive behavioral treatment is more advantageous (p. 807).

More recently, Rice and Harris (2011) also considered the

effectiveness of androgen deprivation therapy (ADT) to reduce

sexual recidivism. In describing the outcomes of surgical and

chemical treatment, the authors acknowledge that voluntary

subjects and weak methodology limit confidence in the out-

comes. Although some studies comparing volunteers with refu-

sers report favorable outcomes using pharmacological ADT,

the authors identify sufficient concerns to conclude that ‘‘ADT

cannot serve as a guarantee against sexually violent recidi-

vism’’ (p. 325). In the cases of men who volunteer and request

ADT, sexual recidivism may be reduced but this may be more

indicative of the characteristics of volunteers rather than the

effects of ADT (p. 328).

In addition to qualified conclusions about the effectiveness

of ADT, the authors recognize legal and ethical issues that sur-

round the use of castration. For example, long-term effects of

ADT on health, sexual behavior, and sexual recidivism remain

a concern among researchers and therapists. In spite of the sup-

port that androgen reduction therapy receives from some thera-

pists, the differential effects experienced by sex offenders and

the methodological limitations of many studies lead Rice and

Harris to conclude that ‘‘Clearly, much more research is needed

before ADT has a sufficient scientific basis to be relied upon as

a principal component of sex offender treatment’’ (p. 328).

Although it is more controversial, surgical castration can be

used in concert with other types of treatment, including psycho-

logical approaches. Although the operation is performed infre-

quently, it has been utilized in Western Europe and in the

United States. In one study of German offenders, Wille and

Beier (1989) found that the surgically castrated offenders

(volunteers) were more likely to refrain from further sexual

offending than offenders who had applied for the surgery but

were denied approval or withdrew their request (Gallagher

et al., 1999, p. 25). Due, in part, to the dearth of studies on this

Kim et al. 107

treatment approach and the lack of a similar control group in

the Wille and Beier study, researchers are reluctant to embrace

its effectiveness (Eher & Pfäfflin, 2011).

Current Study

Although several narrative reviews of sex offender interventions

exist, the most useful are meta-analyses that quantitatively

synthesize the literature. Meta-analyses are characterized by a

number of strengths, including (1) exhaustive literature

searches, (2) an ability to synthesize large literature, (3) a focus

on precise effect sizes rather than solely on statistical signifi-

cance, and (4) an ability to empirically test moderators of study

outcomes and help understand why certain studies had stronger

effects than others (Noar, 2008). Given that the literature of sex

offender treatment has continued to grow at a rapid pace, these

more recent meta-analyses have taken advantage of more

sophisticated analyses that larger literature permit (Noar, 2008).

Craig et al. (2003) previously reviewed six meta-analytic

studies that were published from 1995 to 2002 (Alexander,

1999; Aos, Phipps, Barnoski, & Lieb, 2001; Gallagher et al.,

1999; Hall, 1995; Hanson et al., 2002; Polizzi, MacKenzie,

& Hickman, 1999) and concluded that there were positive

treatment effects in reducing sexual offense recidivism. The

principal purpose of this study is to update the most recent

meta-analyses of sex offender treatments and compare the

findings with those of Craig et al. (2003). This is a replication

of the earlier Craig et al. (2003) study with an expanded sample

of meta-analyses. In addition, this study extends the earlier

review by examining and comparing: (1) effect sizes across the

meta-analytic literature, (2) effect sizes across different target

populations (adolescents vs. adults) in order to examine how

sex offender treatments have performed across populations, and

(3) effect sizes across different types of sex offender treatments.

Method

Search Strategy and Inclusion Criteria

To comprehensively identify meta-analysis studies on sex

offender treatment, the authors conducted a search of a number

of online databases in which criminal justice-related meta-

analyses might plausibly be reported. The intent was to locate

all meta-analyses of sex offender treatments published in peer-

reviewed journals that were available (in print or electronic

form) or in dissertation databases and met criteria for this

review (Noar, 2008).

The search looked for any mention in the title, the abstract,

or the keyword list of the words ‘‘meta-analysis,’’ ‘‘quantitative

review,’’ and ‘‘systematic review,’’ paired with any of the fol-

lowing terms: sex offender treatment or sex offender interven-

tion. The specific databases used were: Criminal Justice

Abstracts, Sociological Abstracts, PsychINFO, MEDLINE,

Social Science Abstracts, Psychology and Behavioral Science

Collections, and Current Contents. In addition, computer and

manual searches identified listings of unpublished materials

(Dissertation Abstracts International, ERIC). The reference

lists of those articles retrieved from each of the databases were

scanned to identify additional studies that may have used

meta-analytic procedures (Lundahl, Taylor, Stevenson, &

Roberts, 2008). The abstracts of likely references were

reviewed to confirm that they used meta-analysis, and an

attempt was made to obtain copies of each of the likely candi-

dates (Wells, 2009).

Meta-analyses were included in the review if they: (1) con-

ducted a meta-analysis (quantitative research synthesis) of

formally developed and evaluated sex offender treatments tar-

geting recidivism; (2) were focused on a defined target popu-

lation of adolescent and adult sex offenders; and (3) examined

outcome variables of sexual recidivism, violent recidivism, or

any recidivism. As a result of these search strategies and

inclusion criteria, a final set of 11 meta-analyses were

included in the current review. Of the 11 meta-analyses, 5

studies were published since 2002 and not included in Craig

et al. (2003).

Effect Size Conversion

Effect size essentially refers to the magnitude of the ‘‘effect’’ of

the program on recidivism (Cohen, 1988). Bigger program

effects (impacts) imply that the program had a greater effect

than smaller effect sizes. The meta-analyses included in this

review used differing effect size indicators. In order to provide

a common metric for interpretation and comparison across all

meta-analyses, effect sizes and confidence intervals in the odds

ratios and r meta-analyses were converted to d using the fol-

lowing equations (Ellis, 2010):

d ¼ 2r ffiffiffi

1 p �r2

and d ¼ log odds ratio� ffiffiffi

3 p

p

Negative effect size indicates recidivism reduction among

intervention participants. One arbitrary criterion used to

determine what constitutes a big effect size as opposed to a

smaller one is that effect sizes of .20 are small, .50 are

medium, and .80 or higher are large (Polizzi et al., 1999).

Cohen (1988) suggests that a small effect of d ¼ .20 is typical of those found in personality, social, and clinical psychology,

while a large effect as d ¼ .80 is more likely to be found in sociology, economics, and experimental or physiological psy-

chology (Cooper, 2010).

Although d is probably one of the best known effect size

indexes, a more compelling way to provide a translation of the

effects of discrete interventions on dichotomous outcomes

(e.g., success or recidivism) is to present the results in a bino-

mial effect size display (BESD) (Cooper, 2010). Developed by

Rosenthal and Rubin (1982), the BESD is a 2 � 2 contingency table where the rows correspond to the independent variable

(e.g., treatment and control) and the columns correspond to any

dependent variable that can be dichotomized (e.g., success or

recidivism). For any given correlation (r), the success rate for

the treatment group is calculated as (.50 þ r/2), while the suc- cess rate for the control group is calculated as (.50 � r/2).

108 TRAUMA, VIOLENCE, & ABUSE 17(1)

In this study, to use the BESD for a standardized mean dif-

ference effect size of d, the effect size of d was converted into

the correlational equivalent using the formula, r ¼ d= p

4 þ d2 (Lipsey & Wilson, 2001). For example, d ¼ .60 is converted to the correlation effect size of .30. So, the value in the success-

treatment cell is .65 (or .50 þ .30/2) and the value in the success-control cell is .35 (or .50 � .30/2). The BESD shows that success was observed for nearly two thirds of the people

who undertook treatment but only a little over one third of

those in the control group (Ellis, 2010). The difference between

the two groups is 30 percentage points, meaning that those who

took the treatment saw an 86% improvement in their success rate (representing the 30 percentage point gain divided by the

35-point baseline; Ellis, 2010). It is easier to comprehend the

magnitude of a relationship if it is expressed as a difference

between a 65% and a 35% success rate than if it is expressed as a correlation effect size of .30 or a standardized mean effect

size of .60.

Results

Table 1 lists characteristics for each of the 11 meta-analyses.

As can be seen, to date three meta-analyses (Gallagher et al.,

1999; Hanson et al., 2002, 2009) included studies conducted

both inside the United States and outside the United States, and

the remaining eight meta-analyses included only American

studies on sex offender treatment. Six meta-analyses included

in Craig et al. (2003) examined the research on sex offender

treatments from as early as 1943 (Doshay, 1969/1943) and as

late as 2000 (Borduin, Schaeffer, & Heiblum, 2000; Hanson

& Nicholaichuk, 2000; Looman, Abracen, & Nicholaichuk

2000; McGuire, 2000; Nicholaichuk, Gordon, Gu, & Wong,

2000; Walker, 2000), while the newly added five meta-

analyses in the current review have examined the research as

late as 2009 (Borduin et al., 2009). In the current review, the

term ‘‘study’’ (represented by the letter k) is used to refer to the

primary intervention trials. This set of meta-analyses typically

treated each research trial as one study (deriving one effect size

from each report), although in some cases trials only reported

data in subgroups (e.g., separately for adolescents and adults),

leading meta-analysts to treat those separate groups as different

‘‘studies’’ (deriving multiple effect sizes from a single report;

Noar, 2008). Using this definition, these meta-analyses have

included as few as 9 studies with a cumulative N ¼ 2,986 (Reit- zel & Carbonell, 2006) and as many as 79 studies with a cumu-

lative N ¼ 10,988 (Alexander, 1999), with a median of k ¼ 22 primary studies.

Efficacy of Sex Offender Treatment

Table 2 is a summary of effect size indices across study out-

comes in the meta-analyses. The effect sizes for the recidivism

measures are listed in the third and fourth columns of the table.

Results from all meta-analyses favored the treatment group. All

effect sizes reported are from fixed effects analyses except for

Gallagher et al. (1999); Hanson, Bourgon, Helmus, and Hodg-

son (2009); and Lösel and Schmucker (2005).

Results indicated that every meta-analysis (Alexander,

1999; Aos et al., 2001; Gallagher et al., 1999; Hall, 1995; Han-

son et al., 2002; Polizzi et al., 1999) examined in Craig et al.

(2003) found significant effects, and the mean effect size was

d ¼ �.20 (range �.11 to �.43), suggesting the sex offender treatments produced an overall 10% reduction in recidivism. The weakest effect was found in Aos et al. (2001), which

synthesized the outcomes of the cognitive behavioral treatment

(k ¼ 25), psychotherapy (k ¼ 6), behavioral treatment (k ¼ 5), chemical treatment (k ¼ 3), and surgical treatment (k ¼ 2) for adults in the United States (see Table 1). The strongest effect

size was found in Gallagher et al. (1999), which synthesized the

outcomes of both psychological therapies (k ¼ 20) and surgical castration (k ¼ 1) and chemical castration/supplemental com- ponent (k ¼ 4) for adolescents and adults in the United States (k ¼ 14), Canada (k ¼ 10), and Germany (k ¼ 1; see Table 1).

The more recent five meta-analyses (Hanson et al., 2009;

Lösel & Schmucker, 2005; Pray, 2002; Reitzel & Carbonell,

2006; Walker, McGovern, Poey, & Otis, 2004) were included

in the current review. Results of these five meta-analyses indi-

cated that every meta-analysis found significant effects, and the

mean effect size was d ¼�.36 (range �.15 to �.80), suggest- ing that the sex offender treatments produced an overall 22% reduction in recidivism. This average effect size of the updated

sample of meta-analyses is 1.77 times bigger than the average

effect size of Craig et al.’s (2003) sample. The weakest effect

size was found in Pray’s (2002) dissertation that synthesized

the outcomes of psychological treatments (k ¼ 10; see Table 1). The strongest effect size was found in Walker et al.

(2004), which synthesized the outcomes of both the psycholo-

gical interventions including MST (k ¼ 1), CBT (k ¼ 3), psy- choeducational therapy (k ¼ 1), and satiation therapy (k ¼ 1) and vicarious sensitization (k ¼ 1) for American adolescents (see Table 1).

Although Craig et al. (2003) found that sexual offender

treatment programs appear to reduce recidivism, what is not

clear is whether this is specific to ages of sex offenders (adult

or adolescent offenders) or particular types of treatments.

Figures 1–4 present heterogeneous information. As shown

in Figures 1 and 2, there appears to be some variability on this

outcome according to target population of sex offender treat-

ments. Three meta-analyses (Aos et al., 2001; Hanson et al.,

2009; Lösel & Schmucker, 2005) that provide the effect sizes

of sex offender treatments of adults in Figure 1 found signif-

icant results, but the grand mean effect size was only d ¼�.15, suggesting that the sex offender treatments for adults pro-

duced an overall 5% reduction in recidivism. As can be seen in Figure 2, five meta-analyses (Aos et al.,

2001; Hanson et al., 2009; Lösel & Schmucker, 2005; Reitzel

& Carbonell, 2006; Walker et al., 2004) that provide the effect

sizes of sex offender treatments of adolescents found signifi-

cant results, and the grand mean effect size was d ¼�.51, sug- gesting that the sex offender treatments for adolescents

produced an overall 24% reduction in recidivism, which is

Kim et al. 109

Table 1. Description of Basic Meta-analytic Study Characteristics by Target Population.

Study Specific Sex Offender Treatment Specific Target Population Years k N

Alexander (1999)

� Relapse prevention (N ¼ 713); group/behavioral (N ¼ 6,616); unspecified (N ¼ 2,054)

� Institutions (N ¼ 2,220); hospital (N ¼ 3,668); community (N ¼ 1,563); unspecified or mixed (N ¼ 1,932)

Male adolescents (N ¼ 1,025); male adults (N ¼ 9,963)

1943–1996 79 10,988

Aos, Phipps, Barnoski, and Lieb (2001)

� Cognitive behavioral with (or without) relapse prevention (k ¼ 25); psychotherapy (k ¼ 6); behavioral (k ¼ 5); chemical treatment (k ¼ 3); surgical treatment (k ¼ 2)

Adult sex offenders 1977–2000 41 6,139 (T); 8,854 (C)

Aos et al. (2001) Juvenile sex offenders treatment—primarily cognitive behavioral

Juvenile sex offenders 1990–2000 11 392 (T); 424 (C)

Gallagher, Wilson, Hirschfield, Coggeshall, and MacKenzie (1999)

� Behavioral (k ¼ 2); augmented behavioral (k ¼ 2); cognitive behavioral/ relapse prevention (k ¼ 10); cognitive behavioral (k ¼ 3); surgical castration (k ¼ 1); chemical castration/ supplemental component (k ¼ 4); other psychological treatment (k ¼ 3)

� Treatment delivered after 1970

Sex offenders; exhibitionists (k ¼ 8); incest offenders (k ¼ 6); pedophiles (k ¼ 16); rapists (k ¼ 13); unspecified mix (k ¼ 5) � Canadian (k ¼ 10);

Americans (k ¼ 14); Germany (k ¼ 1)

� Adolescents (k ¼ 3); adults (k ¼ 22)

� Males (k ¼ 15)

1975–1999 25 NR

Hall (1995) � Cognitive behavioral (k ¼ 5); hormonal (anti-androgen drug or castration; k ¼ 4); group psychotherapy (k ¼ 1); behavioral (k ¼ 4); family therapy (k ¼ 1); individual psychotherapy (k ¼ 1)

� Adolescents (k ¼ 1); adults (k ¼ 11)

1988–1994 12 812 (T); 799 (C)

Hanson et al. (2002)

Psychological treatment (e.g., group therapy, aversive conditioning) � Institutions (k ¼ 23);

community (k ¼ 17); both settings (k ¼ 3)

� Treatment delivered between 1965 and 1999 (80% after 1980)

Sex offenders receiving psychological treatment (note that this study includes sex offenders receiving no treatment or a form of treatment judged to be inadequate or inappropriate) � American (k ¼ 21);

Canadian (k ¼ 16); UK (k ¼ 5); New Zealand (k ¼ 1)

� Adult males (k ¼ 42); adult female (k ¼ 1)

1977–May, 2000 43 5,078 (T); 4,376 (C)

Polizzi, MacKenzie, and Hickman (1999)

Prison-based sex offender treat- ment (k ¼ 8); non-prison- based sex offender treatment (k ¼ 5)

Sex offenders 1988–1997 21 5,542

(continued)

110 TRAUMA, VIOLENCE, & ABUSE 17(1)

Table 1. (continued)

Study Specific Sex Offender Treatment Specific Target Population Years k N

Hanson, Bourgon, Helmus, and Hodgson (2009)

a

Psychological treatments: specialized treatment programs for sex offenders (k ¼ 19); programs designed for general offenders (k ¼ 4) � Institutions (k ¼ 10);

community (k ¼ 11); both settings (k ¼ 2)

� Treatment delivered between 1965 and 2004 (90% after 1980)

� Canadian (k ¼ 12); American (k ¼ 5); UK (k ¼ 3); New Zealand (k ¼ 2); Holland (k ¼ 1)

� Adolescents (k ¼ 4); adults (k ¼ 19)

� Male (k ¼ 20); female (k ¼ 3)

1980–2009 23 3,310 (T); 3,672 (C)

Lösel and Schmucker (2005)a

Treatment did NOT have to be specifically tailored for sexual offenders � Specialized treatment

programs for sex offenders (k ¼ 56)

� Institutions (k ¼ 21); hospital (k ¼ 8); community (k ¼ 27); combination (k ¼ 10)

� Cognitive behavioral (k ¼ 35); classic behavioral (k ¼ 7); insight oriented (k ¼ 5); therapeutic community (k ¼ 8); other psychological, unclear (k ¼ 5); hormonal medication (k ¼ 6); surgical castration (k ¼ 8)

Sex offenders receiving psychological treatment (note that this study includes sex offenders receiving no treatment) � Adolescents only

(k ¼ 7); adults only (k ¼ 36)

1959–2003 69 22,181

Pray (2002)ab Psychological treatments Sex offenders receiving psychological treatment (note that this study includes sex offenders receiving no treatment)

1980–2000 10 924 (T); 695 (C)

Reitzel and Carbonell (2006)

a

Juvenile sexual offender treatment � Average length of treatment ¼ 13.22 months (SD ¼ 4.92); range ¼ 5–18 months

� Institutions (k ¼ 3); community (k ¼ 3); court-based (k ¼ 2); Combination (k ¼ 1)

� Cognitive behavioral/relapse prevention (k ¼ 1); classic cognitive behavioral (k ¼ 2); psychosocial-educational (k ¼ 1); multi-systematic therapy (k ¼ 2); unspecified treatment (k ¼ 1); combination (k ¼ 2)

Juvenile sexual offenders � Male (N ¼ 2,604);

female (N ¼ 121) � mean age ¼ 14.6

(SD ¼ .62) � 41% ¼ a minority race

1975–2003 9 1,301 (T); 1,331 (C);

354 (CT)

Walker, McGovern, Poey, and Otis (2004)a

� Multisystemic therapy (MST; k ¼ 1); Cognitive behavioral therapy (CBT; k ¼ 3); psycho-educational therapy (Psychoeducational; k ¼ 1); satiation therapy (ST; k ¼ 1); vicarious sensitization (VS; k ¼ 1)

Male adolescent sexual offenders

10 644

Note. k ¼ cumulative number of studies; N ¼ largest cumulative sample size reported; NR ¼ not reported; T ¼ treatment group; C ¼ comparison group without treatment; CT ¼ comparison treatment. aStudies not included in Craig et al. (2003). bDissertation.

Kim et al. 111

Table 2. Summary of Meta-analytic Effect Sizes (d) and Standard Error.

Study Population Any Recidivism Sexual Recidivism K

Alexander (1999) Adolescents and adults �.19 (.04) — 79 Aos, Phipps, Barnoski, and Lieb (2001) Adults �.11 (.05) — 7 Aos et al. (2001) Adolescents �.12 (.10) — 5 Gallagher et al. (1999) Adolescents and adults �.43 (NA)a — 25 Hall (1995) Adolescents and adults �.25 (.07) — 12 Hanson et al. (2002) Adults �.12 (.04) — 38 Polizzi, MacKenzie, and Hickman (1999) Adolescents and adults — Treated ¼ 13b

Control ¼ 21 21

c Hanson, Bourgon, Helmus, and Hodgson (2009) Adolescents and adults �.27 (.08)a 13

cHanson et al. (2009) Adolescents and adults �.229 (.084)a 22 c Lösel and Schmucker (2005) Adolescents and adults �.28 (.06)a 49

cLosel and Schmucker (2005) Adolescents and adults �.293 (.064)a 74 c Pray (2002) Adolescents and adults �.15 (.09) 10

cReitzel and Carbonell (2006) Adolescents �.47 (.07) Treated ¼ 7.37b Control ¼ 18.93

9

cWalker et al. (2004) Adolescents �.80 (.09) 10 aRandom Effect Model. bRates of sexual recidivism (%). cStudies not included in Craig et al. (2003).

Figure 1. Forest plot of meta-analytic effect sizes and 95% confidence intervals for recidivism of sex offender treatment for adults.

Figure 2. Forest plot of meta-analytic effect sizes and 95% confidence intervals for recidivism of sex offender treatment for adolescents.

112 TRAUMA, VIOLENCE, & ABUSE 17(1)

almost 3.8 times bigger than the grand mean effect size of sex

offender treatments for adults.

Lösel and Schmucker (2005, p. 121) suggest that sex offender

treatments are not restricted to a certain therapeutic paradigm

but combine strategies from different ‘‘schools in an eclectic

manner’’ and they provide seven modes of sex offender treat-

ment, including cognitive behavioral (including MST), classical

behavioral, insight oriented, therapeutic community (TC),

hormonal medication, surgical castration, and general psycho-

logical treatments (e.g., not specifying a certain psychological

therapeutic paradigm). As can be seen in Figure 3, three meta-

analyses (Aos et al., 2001; Hanson et al., 2009; Lösel &

Schmucker, 2005) that examined nine effect sizes over seven

different types of sex offender treatments found significant

effects for all treatment approaches except insight oriented, gen-

eral psychological, and TC interventions. The weakest effect

size was found in insight-oriented treatment (d ¼ .01), followed by cognitive behavioral (d ¼ �.14), and psychological treat- ment (d ¼�.15). The strongest effect size was found in surgical castration (d ¼�1.51) and hormonal medication (d ¼�.62).

Figure 4 shows the comparison of effect sizes between com-

munity treatments and institutional treatments for sex offenders.

As illustrated in Figure 4, three meta-analyses (Hanson et al.,

2002, 2009; Lösel & Schmucker, 2005) that provide three effect

Figure 3. Forest plot of meta-analytic effect sizes and 95% confidence intervals for recidivism according to the types of sex offender treatment.

Figure 4. Forest plot of meta-analytic effect sizes and 95% confidence intervals for recidivism according to the types of sex offender treatment.

Kim et al. 113

sizes for each treatment type found significant results, except the

effect sizes of community treatment from Hanson et al. (2002)

and institutional treatment from Lösel and Schmucker (2005).

The grand mean effect size of community treatments was d ¼ �.33, suggesting that the sex offender treatments occurring in the community produced about an overall 17% reduction in recidivism, while the grand mean effect size of institutional

treatments was smaller, d ¼ �.20, suggesting about a 10% reduction in recidivism.

Conclusion

The purpose of this study was to review and synthesize

meta-analyses of sex offender treatments designed to reduce

recidivism. One of the most promising findings is that every

meta-analysis in this review found significant recidivism

reduction outcomes. Compared to the Craig et al. (2003) study,

the current review of more recent meta-analyses of sex offen-

der treatment efficacy demonstrated a larger and more robust

sex offender treatment effect in reducing recidivism.

Given PPN’s recommendation, sex offender treatments can

be considered as proven or at least promising. For six meta-

analyses (Alexander, 1999; Aos et al., 2001; Gallagher et al.,

1999; Hall, 1995; Hanson et al., 2002; Polizzi et al., 1999)

examined in Craig et al. (2003), the mean effect size was

d ¼ �.20, suggesting the sex offender treatments produced an overall 10% reduction in recidivism, which meets the pro- mising criteria. The most recent five meta-analyses (Hanson

et al., 2009; Lösel & Schmucker, 2005; Pray, 2002; Reitzel

& Carbonell, 2006; Walker et al., 2004) did find significant

effects, and the mean effect size was d ¼ �.36, suggesting a 22% reduction in recidivism. Thus, it appears that sex offender treatments included in the most recent five meta-analyses are

proven to reduce recidivism. Specifically, the current review

reveals that sex offender treatments for adolescents (d ¼�.51) compared to adults (d ¼�.14), surgical castration (d ¼�1.51), and hormonal medication (d ¼�.62) compared to psychological treatment (d ¼ �.15), and community treatment (d ¼ �.33) compared to institutional treatments (d ¼ �.20) have a larger effect in reducing recidivism.

As indicated in Table 3, this study revealed that there are

effective treatments available for sex offenders, both juvenile

and adult, which reduce recidivism. However, sex offender

treatment appears to be more successful with adolescent rather

than adult offenders. Although the study conclusions are tenta-

tive, they suggest that we now have greater knowledge about

sex offender treatments.

The data reported in this study included recent studies and

updated the published research of Craig et al. (2003) to illus-

trate the effectiveness of treatment approaches for adolescents

and adults. This kind of research is intended to inform treat-

ment programs and to provide data on program effectiveness,

which can be utilized in designing, implementing, and evaluat-

ing new and existing programs. As noted earlier, there are var-

iations in both adolescent and adult sex offenders. Concluding

that their treatment needs are identical suggests a lack of

knowledge about the research on offenders, their backgrounds,

and their behavior.

The current review found that surgical castration and hor-

monal medication have significantly larger effects compared

to the psychological treatments that show significant but small

effect size. Consistent with prior research in this area, the

authors also note the need for more rigorous studies with better

research designs (Hanson et al., 2009). Therefore, these results

must be interpreted cautiously.

As illustrated in Table 4, there are a number of implications

from this study’s conclusions. Most importantly, meta-analytic

evidence demonstrates that there are successful interventions for

adolescent and adult sex offenders. These findings offer support

for existing strategies and strengthen advocates’ request for their

continuation and expansion. The good news is that the five most

recent meta-analyses studies found significant effects suggesting

a 22% reduction in recidivism. Nonetheless, additional research on adolescent and adult sex offender populations is warranted.

This study included a comprehensive array of treatment

techniques that have been employed in the United States and

other countries and compared their effectiveness across the

types of the interventions. Meta-analytic study affords an

opportunity to determine which treatment modalities are most

successful, which allows resources to be allocated to those pro-

grams most likely to reduce recidivism. It is more desirable

than simply treating offenders as though they are homogeneous

and all fit into one treatment program or modality. Based on the

results, sex offender treatments for adolescents compared to

adults have a larger effect in reducing recidivism. These find-

ings suggest that while sex offender treatment should continue

to be supported for juveniles, treatment for adults also needs to

be refined and further developed.

Even if research indicates that specific treatments are effec-

tive in reducing recidivism, ethical considerations or feasibility

might prevent their use. In this study, surgical castration and

hormonal medications were found to be more effective than

psychological treatments. However, there is a reluctance to

endorse them. According to del Busto and Harlow (2011), the

American Medical Association (AMA) is opposed to physi-

cians participating in surgical castration or engaging in medical

practices that serve to punish rather than treat (p. 551). Con-

cerns also focus on whether the treatments violate offenders’

human rights (del Busto & Harlow, 2011, p. 552).

When Daly (2008, p. 206) surveyed state practices for treat-

ing sex offenders, she noted ethical considerations that pre-

clude researchers from randomly assigning offenders to

hormonal treatments that could be intrusive or cause harm as

one of the reasons for the limited research in this area. Only

a few states reported drug use to treat sex offenders, and this

decision was based on a review of individual cases. These con-

cerns suggest that CBT is the preferable treatment modality,

even if it might not be as effective as hormonal medications.

In addition, the most recent meta-analyses demonstrate that

community-based treatments compared to institutional treat-

ments have a larger effect in reducing recidivism. The findings

seem to support legislative reforms that would authorize more

114 TRAUMA, VIOLENCE, & ABUSE 17(1)

sex offender treatments in the community rather than relying

on institutional treatments. Given the punitive approaches that

have characterized the criminal justice system, these changes

may be unlikely. Nonetheless, the evidence demonstrates that

if the public and elected officials were committed to reducing

recidivism, community treatment rather than institutional treat-

ment is proven to reduce recidivism.

This study has some limitations. First, like Craig et al.

(2003), the present review did not include meta-analysis pub-

lished in languages other than English, abstracts from confer-

ence proceedings, or books. The inclusion of unpublished

studies may allow for the investigation of publication bias.

When researchers engage in meta-analysis, they are dependent

on the work of other researchers to a much greater degree than

if they are designing the study and collecting original data. As a

result, interpretations and conclusions are somewhat tentative

(Kim, Merlo, & Benekos, 2013).

Despite these limitations, this study may prove useful to sex

offender treatment practice that seeks to develop a more

evidence-based approach. Specifically, practitioners should

endeavor to treat both juveniles and adults, but recognize that

there is a greater likelihood of reductions in recidivism with ado-

lescents. In terms of recidivism, surgical castration and hormonal

medications have been proven to be effective, but there are seri-

ous ethical issues with them. As a result, there will be more reli-

ance on the psychological approaches like CBT and MST that

were found to be significant in reducing recidivism but had small

effect size when compared to surgical castration and hormonal

medications. The research indicates that treatment in the commu-

nity is more effective than treatment in institutions. Although

there may be obstacles to changing existing exclusionary policies,

evidence demonstrates that sex offenders, both adolescent and

adult, can be treated successfully in community settings.

Finally, additional primary research on various treatment

approaches is required for future meta-analysis to identify

which target groups respond best to specific techniques and

which combination of treatments is most effective. Research

can compare institutional versus community treatments for

adolescent and adult offenders and highlight approaches that

are most likely to reduce recidivism in these settings. Further

study can look at specific age-groups within the target groups.

For example, research could compare younger and older ado-

lescents and adults. The influence of characteristics of each sex

offender treatment approach such as length and frequency of

treatment sessions, materials, and instructors on the effective-

ness of treatment should be addressed in future analyses. With

an emphasis on evidence-based strategies, it is essential to con-

duct more research using meta-analytic techniques to help

inform policy and practice.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to

the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, author-

ship, and/or publication of this article.

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Author Biographies

Bitna Kim is a associate professor in the Department of Criminology

at Indiana University of Pennsylvania. Specific areas of interest

include meta-analytic research, cross-cultural study, gender issues in

CJ system, and victimology. Recent publications have appeared in the

International Journal of Offender Therapy and Comparative Crimin-

ology, Crime & Delinquency, the Journal of Criminal Justice Educa-

tion, the Southwest Journal of Criminal Justice, the Journal of

Criminal Justice, and Violence and Victims.

Peter J. Benekos is a professor of Criminal Justice and Sociology at

Mercyhurst University. He was a visiting professor at Roger Williams

University in Rhode Island. He has conducted research and published

in the areas of juvenile justice, corrections, and public policy. He is the

coauthor (with Alida V. Merlo and Dean John Champion) of The Juve-

nile Justice System: Delinquency, Processing, and the Law, Eighth

Edition, coauthor (with Alida V. Merlo) of Crime Control, Politics

& Policy, Second Edition, and coeditor (with Alida V. Merlo) of Con-

troversies in Juvenile Justice & Delinquency, Second Edition.

Alida V. Merlo is a professor in the Department of Criminology at

Indiana University of Pennsylvania. Previously, she taught at West-

field State University in Westfield, Massachusetts. Her primary

research interests are juvenile justice, criminal justice policy, and

women and the law. She is the coauthor (with Peter J. Benekos and

Dean John Champion) of The Juvenile Justice System: Delinquency,

Processing, and the Law, Eighth Edition, coauthor (with Peter J. Ben-

ekos) of Crime Control, Politics & Policy, Second Edition, and coedi-

tor (with Peter J. Benekos) of Controversies in Juvenile Justice &

Delinquency, Second Edition, coeditor (with Joycelyn M. Pollock of

Women, Law & Social Control, Second Edition.

Kim et al. 117