Risk of depressive disorders associated with medical cannabis authorization: A propensity score matched cohort study

There is an increase in the medical use of cannabis. However, the safety of medical cannabis, particularly for mental health conditions, has not yet been clearly established. Thus, this study assessed the risk of emergency department (ED) visits and hospitalization for depressive disorders among medical cannabis users. We conducted a retrospective longitudinal cohort study of patients who received medical authorization to use cannabis from 2014 to 2019 in Ontario, matched (1:3 ratio) to population-based controls using propensity scores. Conditional Cox regressions were used to assess the association between cannabis authorization and the outcome. A total of 54,006 cannabis-authorized patients and 161,265 controls were analyzed. Approximately 39% were aged under 50 years, 54% were female, and 16% had a history of anxiety or mood disorders. The adjusted hazard ratio (aHR) for depressive disorders was 2.02 (95%CI: 1.83-2.22). The aHR was 2.23 (1.95-2.55) among subjects without prior mental health disorders. The interaction between sex (or age) and exposure was not significant. In conclusion, medical cannabis authorization was associated with an increased risk of depressive disorders. This finding highlights the need for a careful risk-benefit assessment when authorizing cannabis, particularly for patients who seek cannabis to treat a depressive condition.