Comorbidity of Major Depression With Substance Use Disorders

Objectives: In the Canadian adult population, we aimed to 1) estimate the 12-month prevalence of major depressive disorder (MDD) in persons with a diagnosis of harmful alcohol use, alcohol dependence, and drug dependence; 2) estimate the 12-month prevalence of harmful alcohol use, alcohol dependence, and drug dependence in persons with a 12-month and lifetime diagnosis of MDD; 3) identify socioeconomic correlates of substance use disorder-major depression comorbidity; 4) determine how comorbidity impacts the prevalence of suicidal thoughts; and 5) determine how comorbidity affects mental health care used. Methods: We examined data from the Canadian Community Health Survey: Mental Health and Well-Being (CCHS 1.2). Results: The 12-month prevalences of MDD in persons with a substance use disorder (SUD) were 6.9% for harmful alcohol use (95% confidence interval [CI], 5.2 to 8.5), 8.8% for alcohol dependence (95% CI, 6.6 to 11.0), and 16.1% for drug dependence (95% CI, 10.3 to 21.9). Conversely, the 12-month prevalences of harmful alcohol use, alcohol dependence, and drug dependence in persons with a 12-month diagnosis of MDD were 12.3% (95% CI, 9.4 to 15.2), 5.8% (95% CI, 4.3 to 7.3), and 3.2% (95% CI, 2.0 to 4.4), respectively. Regression modelling did not identify any socioeconomic predictors of SUD-MDD comorbidity. Substance dependence and MDD independently predicted higher prevalence of suicidal thoughts and mental health treatment use. Conclusions: SUDs cooccur with a high frequency in cases of MDD. Clinicians and mental health services should consider routine assessment of SUDs in depression patients.