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Does the adapted sex offender treatment programme reduce cognitive distortions? A meta-analysis

Chris Patterson (Bangor University, Bangor, UK)

Journal of Intellectual Disabilities and Offending Behaviour

ISSN: 2050-8824

Article publication date: 12 March 2018




For the 3.8 per cent of people with intellectual disabilities (IDs) who have offended sexually, the main form of treatment is the group-based, cognitive-behavioural, adapted sex offender treatment programme (ASOTP) that focusses on challenging cognitive distortions condoning sex offending. The purpose of this paper is to provide an evaluation of how effective the ASOTP is at reducing ID sex offenders’ cognitive distortions.


Three databases were searched systematically: PsycINFO, MEDLINE and Web of Science. Six studies met the inclusion criteria, yielding 118 participants. Using a random-effects model, effect sizes were calculated using pre- and post-treatment scores on a measure of cognitive distortions. The standardised mean difference (SMD) was 1.77 (95 per cent CI: 1.06, 2.46), which was statistically significant (p<0.001) and “large”. Sensitivity analysis demonstrated that this SMD was robust, and a check for publication bias revealed that it was unlikely that the “file drawer problem” confounded the meta-analysis.


These results indicated that the ASOTP can significantly reduce ID sex offenders’ cognitive distortions, regardless of treatment length, IQ level, language abilities, or offence type. Consistent with earlier reports, longer treatment resulted in the greatest reductions: the optimum treatment length was 24 months.

Research limitations/implications

The ASOTP’s current evidence is comprised wholly of case and quasi-experimental studies, none of which employed control groups. This paper highlights how there is a dire need for high-quality experimental evaluation of the ASOTP.

Practical implications

Clinicians are advised to continue using the ASOTP as the main treatment for ID sex offenders until the effectiveness of the ASOTP is further examined using randomised controlled trials.


This is the first meta-analytic review of the effectiveness of the ASOTP.



Patterson, C. (2018), "Does the adapted sex offender treatment programme reduce cognitive distortions? A meta-analysis", Journal of Intellectual Disabilities and Offending Behaviour, Vol. 9 No. 1, pp. 9-21.



Emerald Publishing Limited

Copyright © 2018, Emerald Publishing Limited

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