Psychological interventions for treatment of adult sex offenders
Authors: Belinda Brooks-Gordon, Charlotte Bilby
Journal: BMJ (2006)

Sexual offending is a public health issue and a social problem. Medical practitioners might assume from the volume of work published on treatments for sex offenders that clinically effective treatments are available. Indeed, psychological treatment is often mandated in the sentencing decision for sexual offenders. Yet the effectiveness of treatments is debated, and evidence for the efficacy of sex offender treatment programmes is often too readily accepted uncritically.1

In conducting a Cochrane meta-analysis on the effects of such psychological interventions we found nine trials that were well conducted in terms of randomisation, blinding, loss to follow-up, and analysis.2 These included randomised controlled trials with a total of 567 male offenders, 231 of whom were followed up for a decade.

The results indicated that studies on behavioural treatments were too small to be informative, although statistically significant improvements were recorded across some groups of offenders.2 Cognitive behavioural group therapy may reduce re-offence at one year for child molesters when compared with standard care, but child molesters had poorer attitudes to treatment during cognitive behavioural therapy than during transtheoretical counselling group therapy. The largest, longest trial compared a group therapy of broadly psychodynamic type with no group therapy for 231 men guilty of paedophilia, exhibitionism, or sexual assault.3 During the subsequent 10 years a greater proportion of those allocated to group therapy were re-arrested, but this did not reach statistical significance.

Evidence from randomised controlled trials provides only a fraction of the knowledge we need, however, particularly on recidivism. Recidivism is used here to mean a repeat sexual offence, whereas reoffending can mean any offence (either more or less serious than the index offence). Treatment failure is associated with higher rates of recidivism, and offenders who successfully complete a treatment programme reoffend less often and less seriously (that is, non-sexual reoffending) than those who do not show that they have understood and worked through the relevant psychological issues.4 Ongoing studies suggest that various types of offenders reoffend differently—for example, paedophilic versus non-paedophilic child molesters (those with an erotic attachment to children versus those without erotic attachment but who may, for example, be aroused by violence).5

Randomised controlled trials are difficult to carry out in criminal justice settings, and researchers often conduct quasi-experiments instead. We assessed the quality of these and non-randomised controlled trials with matched and non-matched controls, including 21 quasi-experimental studies from the UK, USA, Canada, and Europe. Of these, seven studies showed a statistically significant treatment effect and 10 did not. In four studies the data were not clear enough to analyse.

Most participants in matched trials where a significant treatment effect was found were allocated to treatment groups according to sentencing decision and post-sentencing risk assessment. Most of these studies were matched retrospective trials carried out on offenders in the criminal justice system; matching was done retrospectively. Matching offenders with a control group is problematic and can threaten the quality of the research. The results here were equivocal: more studies found no statistically significant treatment effect than found a significant effect.

A randomised controlled trial of a complex programme will not distinguish which components are a success or failure, whereas qualitative studies can provide understanding about how treatment is received and adhered to. Little sound qualitative research on how offenders use and engage with treatment has been done. We systematically reviewed four qualitative studies that complied with the guidelines of the Cochrane critical appraisal skills programme.2 Three were process evaluations,6-8 and in two of these data were analysed using grounded theory7,8; one was an exploratory study that used thematic content analysis.9 These studies yielded valuable findings, including crucial contextual information on factors which facilitated and impeded treatment.

Sexual offending, like many medical conditions, cannot be cured. Better understanding of the outcomes of treatments—either controlling and moderating or harming and worsening behaviour—could at least focus resources on the most beneficial and cost effective interventions.

There is enormous political and institutional pressure to prove that treatment works. Assessment of all outcomes must take the expectations of researchers into account, and also offenders' and therapists' perceptions of treatment. And, because recidivism is a proxy measure of reoffending (that is, reoffending may continue for a long period without re-conviction), more sophisticated multi-method outcome measures should be included in research designs.10

It should be possible to combine the strength of randomised controlled trials with the collection of good qualitative process data11 and to ensure that psychological interventions for sex offenders are assessed using the realistic evaluation formula of: outcome = mechanism+content.12 These concepts help the researcher to consider the dynamics of an intervention: the “context” in which it is set and the “mechanism” of the intervention, thereby ensuring that we are better able to assess what element of treatment is effective in changing the behaviour of offenders.