A Cochrane review included 32 studies with a total of 3165 participants. Three trials were set exclusively in hospital and 19 in the community, 8 trials recruited patients or were conducted in both the community (outpatients) and in hospital and two were set in the community and in jail. All participants were adults with the majority having a diagnoses of schizophrenia, schizoaffective disorder or psychosis. All had a current diagnosis of substance use disorder or had documented evidence of substance misuse. Interventions were integrated models of care (4 RCTs), non-integrated models of care (4 RCTs), combined cognitive behavioural therapy and motivational interviewing (7 RCTs), cognitive behavioural therapy (2 RCTs), motivational interviewing (8 RCTs), contingency management (2 RCTs) and skills training (2 RCTs). There was no significant differences on loss to treatment (RR 1.09 CI 0.82 to 1.45; 3 RCTs, n=603), death by 3 years (RR 1.18, CI 0.39 to 3.57; 2 RCTs, n=421), alcohol use (not in remission at 36 months) (RR 1.15, CI 0.84 to 1.56; 1 RCT, n=143), substance use (RR 0.89, CI 0.63 to 1.25; 1 RCT, n=85), global assessment of functioning (MD 0.7, CI 2.07 to 3.47; 1 RCT, n=171), or general life satisfaction (MD 0.02 higher: CI 0.28 to 0.32; 2 RCTs, n=372). For evaluation of non-integrated intensive case management with usual treatment (4 RCTs, n=163) there was no significant difference for loss to treatment at 12 months (RR 1.21, CI 0.73 to 1.99; 3 RCTs, n=134). Motivational interviewing plus cognitive behavioural therapy compared to usual treatment (7 RCTs, n=878) did not reveal any advantage for retaining participants at 12 months (RR 0.99, CI 0.62 to 1.59; 1 RCT, n=327) or for death (RR 0.72, CI 0.22 to 2.41; 3 RCTs, n=493), and no benefit for reducing substance use (MD 0.19, CI -0.22 to 0.6; 1 RCT, n=119), relapse (RR 0.5, CI 0.24 to 1.04; 1 RCT, n=36) or global functioning (MD 1.24, CI 1.86 to 4.34; 4 RCTs, n=445). Cognitive behavioural therapy alone compared with usual treatment showed no significant difference for losses from treatment at 3 months (RR 1.12, CI 0.44 to 2.86; 2 RCTs, n=152). No benefits were observed on measures of lessening cannabis use at 6 months (RR 1.30, CI 0.79 to 2.15; 1 RCT, n=47) or mental state (Brief Psychiatric Rating Scale MD 0.52, CI -0.78 to 1.82; 1 RCT, n=105). There was no advantage for motivational interviewing alone compared with usual treatment (8 RCTs, n=509) in reducing losses to treatment at 6 months (RR 1.71, CI 0.63 to 4.64; 1 RCT, n=62), although significantly more participants in the motivational interviewing group reported for their first aftercare appointment (RR 0.69, CI 0.53 to 0.9; 1 RCT, n=93). Some differences, favouring treatment, were observed in abstaining from alcohol (RR 0.36, CI 0.17 to 0.75; 1 RCT, n=28) but not other substances (RR -0.07, CI -0.56 to 0.42; 1 RCT, n=89), and no differences were observed in mental state (MD 0.19, CI -0.59 to 0.21; 1 RCT, n=30). There were no significant differences for skills training in the numbers lost to treatment by 12 months (RR 0.70, CI 0.44 to 1.1; 2 RCTs, n=94). There were no differences for contingency management compared with usual treatment (2 RCTs, n=206) in numbers lost to treatment at 3 months (RR 1.65, CI 1.18 to 2.31; 1 RCT, n=176), number of stimulant positive urine tests at 6 months (RR 0.83, CI 0.65 to 1.06; 1 RCT, n=176) or hospitalisations (RR 0.21, CI 0.05 to 0.93; 1 RCT, n=176).
Comment: The quality of evidence is downgraded by inconsistency (heterogeneity in patients and interventions) and imprecise results (few trials for each comparison).