Anger has been shown to be associated with aggression and violence in adults with intellectual disabilities in both community and secure settings. Emerging evidence has indicated that cognitive behavioural anger treatment can be effective in reducing assessed levels of anger and violent behaviour in these patient populations. However, it has been suggested that the effectiveness of these types of interventions is influenced by the experience and training of the therapists.

In this service evaluation study, the pre- and post-treatment and 12-month follow-up assessment scores of 88 detained in-patient adults with intellectual disabilities and forensic histories who received cognitive behavioural anger treatment were examined in order to investigate whether participants’ responsiveness to treatment was associated with treatment being delivered by qualified versus unqualified therapists.

Overall significant reductions in self-reported measures of anger disposition and anger reactivity were found with no significant time × therapist experience interaction effects. However, the patients treated by qualified therapists improved significantly on measures of anger control compared with those allocated to unqualified therapists.

Male and female detained patients with intellectual disabilities and forensic histories can benefit from an individual cognitive behavioural anger treatment intervention delivered by qualified and unqualified therapists, but therapist experience may be important in supporting patients to develop more complex anger control coping skills.