Anxiety and mood disorders and cannabis use.

<h4>Background</h4>Cannabis use has been linked to anxiety and mood disorders (AMD) in clinical cases, but little research on this relationship has been reported at the epidemiological level.<h4>Objectives</h4>We examined the relationship between self-reported frequency of cannabis use and risk for AMD in the general Ontario adult population.<h4>Methods</h4>Data were based on the CAMH Monitor survey of Ontario adults from 2001 to 2006 (n = 14,531). AMD was assessed with the 12-item version of the General Health Questionnaire (GHQ12). Frequency of cannabis use within the past year was grouped into five categories: No use (abstainer), less than once a month but at least once a year, less than once a week but at least once a month, less than daily but at least once a week, almost every day to more than once a day. Logistic regression analysis of AMD and cannabis use was implemented while controlling for demographics and alcohol problems.<h4>Results</h4>AMD was most common among heavy cannabis users (used almost every day or more) (18.1%) and lowest for abstainers (8.7%). Compared to abstainers, the risk of AMD was significantly greater for infrequent cannabis users (OR = 1.43) and heavy cannabis users (OR = 2.04) but not for those in between.<h4>Conclusion</h4>These data provide epidemiological evidence for a link between both light and heavy cannabis use and AMD.<h4>Scientific significance</h4>Recognizing the comorbidity of heavy cannabis use and AMD should facilitate improved treatment efforts. Our results also suggest the possibility that, for some individuals, AMD may occur at relatively low levels of cannabis use.