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Ineffective treatment of sex offenders fails victims

BMJ 2015; 350 doi: (Published 27 January 2015) Cite this as: BMJ 2015;350:h199

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Sex Offender Treatment: Commentary on Ho

The field of sex offender treatment outcome research is characterised by much debate. Some reviewers have concluded that the accumulation of evidence derived from observational studies indicates that psychological treatments reduce recidivism (Hanson et al., 2002; Lösel & Schmucker, 2005). Others however have adopted more parsimonious appraisals, concluding that the evidence is insufficient, or that scientific designs are below what is required for the outcome data to be minimally informative (Kenworthy, Adams, Brooks-Gordon, & Fenton, 2004; Rice & Harris, 2003). Results from recent systematic reviews indicate that better quality research is required before we can conclude on whether such programmes are effective or not (Walton & Chou, 2014; Långström et al. 2013; Dennis et al. 2013). In his personal view, Dr Ho does not appear to have fully considered the current need for improved research designs in supporting the conclusion that treatment is ineffective. Ho focuses his attention on the National Offender Management Services’ (NOMS) suite of accredited Sex Offender Treatment Programmes (SOTPs). In particular, he briefly reports on the ‘Core Programme’, suggesting that there is a current lack of evidence to indicate the intervention is effective at reducing recidivism. In this response, we draw attention to the state of affairs in the literature, and in particular the problems inherent with fixed claims about effects of treatment, when these are borne out of suboptimal studies fraught with systematic bias which threatens the validity of inferences drawn.

It is perhaps first important to clarify the conclusions drawn by the authors of the systematic review and meta-analysis Ho refers to in supporting his assertion that the Core Programme is ineffectual. Incidentally, the other piece of evidence he refers to (Ho & Ross, 2012) is an editorial criticising the NOMS “fact sheet” of outcome evidence. In our view, this has already been satisfactorily rebutted by Mann, Carter & Wakeling (2012). In following, Lösel and Schmucker (2005), whilst including in their data synthesis, one observational study that investigated the effect of the Core Programme on recidivism (Friendship et al., 2003), concluded that cognitive-behavioural interventions (incidentally, a therapeutic modality central to the Core programme itself) were more effective than other psychosocial approaches. Hence, it is curious that Ho draws on this meta-analysis to support his position that treatment is ineffective. On the contrary, there is a need for cautious interpretation of Lösel and Schmucker’s findings, given that the majority of included studies (60%) were rated as methodologically weak owing to the non-equivalence of comparison and treatment groups. In a field laden with weak inference studies, literature can become matted with biased outcomes, due to decisions taken in scientific design, which either artificially inflate or decrease the chances of finding a treatment effect. With observational designs especially, non-comparable groups are observed or supposed based on actual or a prior group differences which directly impact outcomes of interest independent of treatment. Therefore, there is a need to determine the direction of overall systematic bias on the observed recidivism rates (Walton & Chou, 2014). Notwithstanding their optimistic findings, the conclusion that Lösel and Schmucker (2005) support is the need for the implementation of more randomised studies.

Randomised Controlled Trials (RCTs) have been regarded as the optimal design for treatment evaluation (Harris, Rice & Quinsey, 1998; Rice & Harris, 2003; Seto et al., 2008; although see Hollin, 2008; Marshall, 2006; Marshall & Marshall, 2007; 2008 for an alternative view). Randomised assignment should offset differences that exist between large groups as well as inadvertent bias caused by the researcher during allocation. Dennis et al. (2013) limited their inclusion criteria to RCTs and concluded that there was the need for further randomised studies, since current available evidence does not support the belief that treated individuals pose a reduced risk of recidivism. Only two of the ten randomised studies they included reported recidivism rates. Results from the most well recognised randomised study reporting final data from the Sex Offender Treatment and Evaluation Project (SOTEP, Marques et al. 1994; Marques et al. 2005), indicate that a structured relapse prevention (RP) therapy has no effect on recidivism. The extent to which the SOTEP represents current treatment practice is debatable (see Seto et al. 2008; Marshall & Marshall, 2007; 2008). Nevertheless, important learning from the SOTEP has been documented (Marques et al. 2000). Certainly, dynamic risk factors (Hanson & Morton-Bourgon, 2004; 2005) which are now popularised treatment targets in modern interventions were either absent or deficient. In addition, the RP model has been criticised (Laws Hudson & Ward, 2000; Yates, 2007), and among international treatment programmes (see McGrath et al. 2010) is becoming gradually replaced by future-orientated approaches (Ward, Mann & Gannon, 2007) and the self-regulation (SR) model of relapse (Ward & Hudson, 2000). The second RCT showed that a group psychodynamic intervention had no effect on recidivism (Romero, 1983). This therapeutic modality has been replaced by cognitive-behavioural approaches, and is not representative of current practice (McGrath et al. 2010). In light of these unfavourable results, no randomised trials of primary adult sex offender treatments have been completed in what is fast approaching two decades. The bearing that results from dated interventions have on the efficacy of current treatments is debatable. Reliance on weak scientific designs, often poorly implemented, has it seems delayed the gathering of generally agreed upon knowledge. Therefore, incautious assertions about treatment effects or lack thereof, are premature until either more randomised designs are carried out or the standards of observational studies are improved such that bias is significantly reduced.

Friendship et al. (2003) have reported results that indicate the Core Programme is effective for medium risk offenders. No effects were found for higher risk offenders; a group which according to the risk principle (Bonta & Andrews, 2007) would require a higher dose of treatment than the Core Programme alone. However, these data were drawn from an observational study which has either been rated as methodologically weak (Lösel & Schmucker, 2005; Hanson et al. 2009), or excluded from systematic reviews on basis of its suboptimal design status. Therefore, bias is likely to have impacted results. NOMS cognitive-behavioural interventions for sexual offenders are centralised around Risk, Need and Responsivity principles. The clinical landscape of commissionable SOTP provision is now entering into a period of considerable change reflecting up to date intervention targets, and a need to effectively prioritise finite resources for offenders who are most likely to benefit. Use of strong inference designs to evaluate recidivism rates for offenders treated on these developing programmes would provide clearer indication as to their impact on recidivism than could be established for their predecessor.

Despite the inconsistent findings in the field, even for those preferring to rely on the most rigorous of randomised scientific trials, of which very few exist, one should be cautious as not to hastily conflate absence of evidence, with evidence of absence. Doing so increases risk of Type II error. Given that for various political and logistical reasons, observational designs will likely continue to be used in place of randomised trials, we have outlined ways forward for improvement in their implementation, so that internal validity is enhanced and greater confidence can be gained from outcome results (Walton & Chou, 2014). In our view it is also important that systematic reviewers and programme evaluators make an effort to assess the direction of bias on observed outcomes an essential part of their analytical procedure. Where directions of bias significantly diverge between individual sets of data, statistical aggregation of such data is at increased risk of being misleading. Therefore, at the very least, this process reduces chances of such misinformed analyses, and at best may have the potential to inform patterns between observed outcomes and decisions taken in scientific design. We believe that Ho’s conclusion is premature. Claiming that treatment is ineffective in the absence of consistent high quality evidence to support such a claim does not accurately convey the state of affairs in the field. Only through increasing the rigor of studies in the field together with efforts to identify the influence of residual bias on outcomes of interest can progress occur.


Dr Jamie Walton
Registered Practitioner Psychologist (Forensic) and Chartered Psychologist
HM Prison Service
North West Area Psychological Services

Dr Shihning Chou
Assistant Professor of Forensic Psychology,
Centre for Forensic and Family Psychology,
Division of Psychiatry & Applied Psychology, School of Medicine, University of Nottingham
Floor B, Yang Fujia Building, Jubilee Campus, Wollaton Road, Nottingham, NG8 1BB, UK

Jamie Walton is employed in HM Prison Service and is a current Treatment Manager of the Core Sex Offender Treatment Programme (SOTP) within a regional Treatment Management team. The commentary submitted represents his own views together with those of Shihning Chou and not intended to directly represent the views of HM Prison Service or the National Offender Manager Service.


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Competing interests: No competing interests

13 April 2015
Jamie. S. Walton
Registered Practitioner Psychologist (Forensic) and Chartered Psychologist
Shihning Chou (Assistant Professor of Forensic Psychology, University of Nottingham)
HM Prison Service, North West Area Psychological Services