Reasons for cannabis use and effects of cannabis use as reported by patients with psychotic disorders.

BACKGROUND: Cannabis is one of the most commonly used substances in patients with a psychotic disorder and is associated with a higher risk of psychotic relapses. Identifying reasons for cannabis use and subjective effects in patients with psychotic disorders can provide insight into the functions of cannabis use, and this may lead to targeted interventions.
METHODS: A literature search of the PubMed and PsycINFO databases for articles published from 1985 till 2008 was carried out to review studies that examined self-reported reasons for cannabis use and self-reported effects of cannabis use in patients with psychotic disorders.
RESULTS: Only a few studies were found that specifically assessed reasons for and effects of cannabis use. Despite the heterogeneity in the study samples and methodology, patients commonly reported that their reasons for cannabis use were enhancement of positive affect, relief of dysphoria and social enhancement. Fewer patients reported reasons related to relief of psychotic symptoms or relief of side effects of medication. Frequently reported positive effects of cannabis were positive changes in affect and relaxation. A large proportion of patients reported that cannabis negatively affected positive symptoms.
CONCLUSIONS: Patients suffering from psychotic disorder report using cannabis mainly for affect regulation and socialization, despite the awareness that cannabis has a negative effect on positive symptoms. In spite of the heterogeneity of the studies, the results turned out to be broadly comparable and support the external validity of this review to a broad range of cannabis-using patients with psychotic disorder. Copyright 2009 S. Karger AG, Basel.