We included 25 RCTs and found no compelling evidence to support any one psychosocial treatment over another to reduce substance use (or improve mental state) by people with serious mental illnesses. Furthermore, methodological difficulties exist which hinder pooling and interpreting results; high drop out rates, varying fidelity of interventions, varying outcome measures, settings and samples and comparison groups may have received higher levels of treatment than standard care. Further studies are required which address these concerns and improve the evidence in this important area.
Cognitive-behavioural therapy for substance use disorders in people with psychotic disorders: Randomised controlled trial.
Few randomised controlled trials have been aimed specifically at substance use reduction among people with psychotic disorders.
                To investigate whether a 10-session intervention consisting of motivational interviewing and cognitive-behavioural therapy (CBT) was more efficacious than routine treatment in reducing substance use and improving symptomatology and general functioning.
                A community sample of people with a psychotic disorder and who reported hazardous alcohol, cannabis and/or amphetamine use during the preceding month was recruited. Participants were randomly allocated to motivational interviewing/CBT (n = 65) or treatment as usual (n = 65), and were assessed on multiple outcomes at baseline, 15 weeks, 6 months and 12 months.
                There was a short-term improvement in depression and a similar trend with regard to cannabis use among participants who received the motivational interviewing/CBT intervention, together with effects on general functioning at 12 months. There was no differential benefit of the intervention on substance use at 12 months, except for a potentially clinically important effect on amphetamine use.
                The motivational interviewing/CBT intervention was associated with modest improvements.