Treatment of cannabis use disorders in people with schizophrenia spectrum disorders - A systematic review

BACKGROUND: Cannabis use disorders (CUD) are prevalent among people with schizophrenia spectrum disorders (SSD), with a range of detrimental effects, e.g. reduced compliance to medication and psychosocial interventions, and increased level of psychotic-dimension symptoms. The aim of this study was to review literature on treatments of CUD in SSD-patients. METHODS: PubMed, PsycINFO, EMBASE, and The Cochrane Central Register of Controlled Trials were searched. RESULTS: 41 articles were selected, 11 treating cannabis as a separate outcome. Contingency management was only effective while active. Pharmacological interventions appeared effective, but lacked randomized controlled trials (RCTs). Psychosocial interventions, e.g. motivational interviewing and cognitive behavior therapy (CBT), were ineffective in most studies with cannabis as a separate outcome, but effective in studies that grouped cannabis together with other substance use disorders. CONCLUSIONS: Insufficient evidence exists on treating this form of dual-diagnosis patients. Studies grouping several types of substances as a single outcome may overlook differential effects. Future RCTs should investigate combinations of psychosocial, pharmacological, and contingency management.