Thirty-one studies (more than 470 participants) were included. The studies were classified as case studies/series (11 studies, n=17), larger outcomes studies (8 studies, n=199), interventions of groupwork (8 studies, n=83) and retrospective studies (4 studies, n>171).
The included studies had methodological flaws: e.g. small sample size, lack of control group, use of multi-modal interventions making it impossible to identify any successful component, and lack of a formal assessment of the outcomes. In addition, the retrospective studies were subject to interpretation bias. These methodological flaws severely limit the reliability of the results presented.
Case studies.
Nine of the 11 studies reported no recidivism; these evaluated cyproterone acetate therapy, residential programmes for transferred prisoners, psychotherapy, cognitive group therapy, risperodone and multi-modal therapies. One case study reported an episode of 'irresponsible behaviour' but no offending after assisted covert sensitisation and individual counselling; a second reported an incidence of stalking after individual cognitive therapy; a third reported an increased interest in children with a reduction in the dose of medroxyprogesterone; and a fourth reported no offences, but a continuation of sexual behaviour after therapy with selective serotonin receptor inhibitors.
Larger outcomes studies.
Where reported, the rate of recidivism with treatment ranged from 0 to 30.8% (5 studies). One study reported a rate of 66% when treatment with anti-androgen was stopped, and another 84% within 12 months of a prison regime. Studies that did not report recidivism reported improvements in relationships with other prisoners or staff or in behaviour (3 studies).
Interventions of groupwork.
Where reported, the rate of recidivism with treatment ranged from 0 to 57.14% (6 studies). Studies that did not report recidivism reported improvements in cohesion and attendance and participation (2 studies).
Retrospective studies.
Where reported, the rate of recidivism with treatment ranged from 23 to 84.2% (3 studies). The fourth study reported a reduction in incidents in 8 of the 19 cases followed up.