Bridging Disciplinary Boundaries (January 11 - 14, 2007)

BACKGROUND. The association between cannabis dependence and major depression is often understood as misdiagnosed expected effects of heavy cannabis use mistaken for depressive syndromes. To investigate whether this could account for the entire relationship, the association of past cannabis dependence with past-year DSM-IV major depression (ie, non-overlapping time frames) was investigated in individuals who no longer use drugs and who drank no more than small amounts. We conducted the study using data from the National Epidemiologic Survey on Alcohol and Related Conditions, a representative sample. METHODS. Former cannabis users who did not use drugs in the last 12 months and who drank no more than 12 drinks in the last 12 months (n=1,887) were divided into those with (n=170) and without (n=1,717) past cannabis dependence. Logistic regression was used to test the association between prior cannabis dependence and current major depression, controlling for demographic characteristics. RESULTS. Past cannabis dependence significantly increased the risk of current major depressive disorder (OR=1.93, CI, 1.16-3.21). This relationship was not attenuated by control variables. CONCLUSION. The strong association between past cannabis dependence and past-year major depression is not entirely an artifact of misdiagnosed expected effects of heavy use. These findings provide important prevention and treatment implications for individuals with cannabis dependence.