Examining the Relationship Between Cannabis Use and Mood, Anxiety, and Psychotic Symptoms in Psychiatric Patients with Severe Concurrent Mental Health and Substance Use Disorders Before and After Recreational Cannabis Legalization in Canada.

Objective: The relationship between cannabis use and mental health has garnered significant attention in recent decades. However, studies have largely been in general populations or in countries in which recreational cannabis use is illegal. Method: The current cross-sectional study examines the relationship between cannabis use, mood disorders, anxiety, and psychosis in an inpatient psychiatric population with severe concurrent mental health and substance use disorders, exploring the potential moderating effect of the legalization of recreational cannabis in Canada. Results: Cannabis use compared to non-use was associated with higher self-reported depression, anxiety, and psychotic symptoms but was not associated with diagnosis of a mood, anxiety, or psychotic disorder. Frequency of cannabis use was unrelated to mental health outcomes, but age of first use was negatively associated with self-reported psychoticism symptoms. There were some significant associations between recreational cannabis legalization and mental health, but legalization was largely unrelated to outcomes. There were also some significant differences by demographics. Conclusions: While findings are relatively consistent with prior literature, some significant associations differed, suggesting the importance of examining concurrent disorder patients as a unique population when examining relationships between cannabis use and mental health.