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

Background: There is an increase in medical cannabis use, including individuals with depressive disorders, while the risk of depressive disorders associated with medical cannabis use is not yet clearly established.

Objectives: Thus, this study assessed the risk of emergency department visits and hospitalization for depressive disorders among medical cannabis users.

Methods: Retrospective longitudinal cohort study of patients who received medical cannabis authorization for care from 2014 to 2020 in Ontario. These patients were matched to selected controls from the general population using propensity scores. Patients were followed from cannabis authorization' date to assess the occurrence of emergency department visits or hospitalizations with a primary diagnosis code of depressive disorder. Cox proportional hazards regression was used to assess the association between cannabis authorization and outcome.

Results: A total of 60,414 patients authorized to use cannabis, matched to 180,397 controls were included. Approximately 39% were under 50 years of age, 54% were female, and 9% had an history of emergency department visits/hospitalization for mental disorders. The incidence of emergency department visits/hospitalizations was 6.27/1000 person-years and 3.05/1000 person-years in cannabis and controls groups, respectively. Association between cannabis authorization and depressive disorders was significant with an adjusted hazard ratio of 1.94 (95% CI 1.72-2.13). Among subjects without history of mental health disorders, the hazard ratio was 1.89 (95% CI 1.70-2.09).

Conclusions: Authorization of medical cannabis was associated with an increased risk of emergency department visits or hospitalizations for depressive disorders. A risk assessment when authorizing cannabis should take this observation into account.