Marijuana Use and the Risk of Major Depressive Episode. Epidemiological Evidence from the United States National Comorbidity Survey

Background: This is an epidemiological study of a possible causal role of marijuana use in the development of Major Depressive Episode (MDE). Male-female differences in the suspected causal association have also been studied.

Method: Data are from 6,792 National Comorbidity Survey participants aged 15-45 years, assessed via the University of Michigan modified version of the Composite International Diagnostic Interview (UM-CIDI). Survival analysis methods were used to estimate cumulative risk of MDE by levels of marijuana use and to estimate suspected causal associations after adjustment for other influences.

Results: The risk of first MDE was moderately associated with the number of occasions of marijuana use and with more advanced stages of marijuana use. Relative to never users, non-dependent marijuana users had 1.6 times greater risk of MDE (95 % Confidence Interval: 1.1, 2.2), even with statistical adjustment for sex, birth cohorts, alcohol dependence, and history of daily tobacco smoking.

Conclusions: There was male-female variation in the degree of association between stage of marijuana involvement and MDE, but the strength of the association is modest at best.