Temporal Changes in the Cross-Sectional Associations between Cannabis Use, Suicidal Ideation, and Depression in a Nationally Representative Sample of Canadian Adults in 2012 Compared to 2002

Background: With the recent legalization of nonmedical cannabis in Canada, it is important to document previous associations between cannabis use and major depressive episode and suicidal ideation, as well as the extent to which these associations have changed over time. Methods: This study uses pooled data from the 2002 and 2012 Canadian Community Health Survey's Mental Health Component, which are repeated cross-sectional surveys of nationally representative samples of Canadians 15 to 60 years of age (n = 43,466). Binary logistic regression was performed, applying weighting and bootstrapping, to examine the association between at least monthly use of cannabis and past 12-month suicidal ideation and major depressive episode (MDE). Results: At least monthly nonmedical cannabis use was associated with an increased odds of MDE and suicidal ideation, and both associations strengthened in 2012 compared to 2002. Canadians using cannabis at least once a month in 2012 had 1.59 (95% confidence interval [CI], 1.11 to 2.27) times the odds of experiencing suicidal ideation and 1.55 (95% CI, 1.12 to 2.13) times the odds of experiencing MDE compared to those who used cannabis at least once a month in 2002. This temporal change remained after controlling for other substance use. Conclusions: Monthly cannabis use was consistently related to both suicidal ideation and MDE, and these associations were stronger in 2012 compared to 2002. The findings of this study provide a baseline for the association between cannabis use and suicide and depression in the Canadian population that should be reevaluated now that nonmedical cannabis has been legalized.