AIM: This study is a report of a systematic review to assess current evidence for the efficacy of psychosocial interventions for reducing substance use, as well as improving mental state and encouraging treatment retention, among people with dual diagnosis.

BACKGROUND: Substance misuse by people with a severe mental illness is common and of concern because of its many adverse consequences and lack of evidence for effective psychosocial interventions.

DATA SOURCES: Several electronic databases were searched to identify studies published between January 1990 and February 2008. Additional searches were conducted by means of reference lists and contact with authors.

REVIEW METHODS: Results from studies using meta-analysis, randomized and non-randomized trials assessing any psychosocial intervention for people with a severe mental illness and substance misuse were included.

RESULTS: Fifty-four studies were included: one systematic review with meta-analysis, 30 randomized controlled trials and 23 non-experimental studies. Although some inconsistencies were apparent, results showed that motivational interviewing had the most quality evidence for reducing substance use over the short term and, when combined with cognitive behavioural therapy, improvements in mental state were also apparent. Cognitive behavioural therapy alone showed little consistent support. Support was found for long-term integrated residential programmes; however, the evidence is of lesser quality. Contingency management shows promise, but there were few studies assessing this intervention.

CONCLUSION: These results indicate the importance of motivational interviewing in psychiatric settings for the reduction of substance use, at least in the short term. Further quality research should target particular diagnoses and substance use, as some interventions may work better for some subgroups.