Treatment of Cannabis Use Among People with Psychotic or Depressive Disorders: a Systematic Review

Objective: This article systematically reviews the evidence from randomized controlled trials (RCTs) for pharmacologic and psychological approaches to the treatment of cannabis use among individuals with psychotic or depressive disorders.

Data Sources: A systematic literature search was conducted using the PubMed and PsychINFO databases from inception to December 2008. Individual searches in cannabis use (search terms: marijuana, cannabis, marijuana abuse, cannabis abuse, marijuana usage, cannabis usage), mental disorders (search terms: mood disorders, affective disorders, anxiety disorders, anxiety, depressive disorder, depression, psychotic disorders, psychosis, mental disorders), and pharmacotherapy (search terms: medication, drug therapy, pharmacotherapy, psychopharmacology, clinical trials, drug trial, treatment trial) were conducted and limited to humans, adolescents and adults.

Study Selection: A search combining the individual cannabis use, mental disorder and pharmacotherapy searches produced 1,713 articles (PubMed = 1,398; PsychINFO = 315). Combining the cannabis use and mental disorder searches while limiting them to English articles and RCTs produced a total of 286 articles (PubMed = 228; PsychINFO = 58). From this literature, there were 7 RCTs conducted among mental health clients that reported cannabis use outcomes using pharmacologic or psychological interventions.

Data Synthesis: While few RCTs have been conducted, there is evidence that pharmacologic and psychological interventions are effective for reducing cannabis use in the short-term among people with psychotic disorders or depression.

Conclusions: Although it is difficult to make evidence-based treatment recommendations due to the paucity of research in this area, available studies indicate that effectively treating the mental health disorder with standard pharmacotherapy may be associated with a reduction in cannabis use and that longer or more intensive psychological interventions rather than brief interventions may be required, particularly among heavier users of cannabis and those with more chronic mental disorders. Specific recommendations regarding the type and length of specific psychological treatments cannot be made at this time, although motivational interviewing and cognitive-behavioral therapy approaches appear most promising.