Comorbid substance use disorder, major depression, and associated disability in a nationally representative sample.

BACKGROUND: Major depression episodes (MDE) and substance use disorders (SUDs) are commonly linked to disability, but there is a lack of research on the risk of disability among individuals who have both SUDs and MD in the general population. This study aimed to investigate the associated risk of disability in people with comorbid SUDs- specifically cannabis use disorder, alcohol use disorder, other drug (except cannabis) use disorder, and a major depressive episode using a nationally representative sample.

METHODS: The 2012 Canadian Community Health Survey- Mental Health (CCHS-MH) data were analyzed using multilevel logistic regression models. The survey included a nationally representative sample of Canadians aged 15 years and older (n = 25,113) residing in the ten Canadian provinces from January to December 2012. The diagnoses of MDE and the SUDs were derived from the DSM-IV diagnostic criteria using a modified WHO-CIDI instrument, while disability was assessed using the World Health Organization Disability Assessment Score (WHODAS) 2.0.

RESULTS: The strongest predictor of disability was found to be comorbidity. Individuals diagnosed with both a SUD and MDE were respectively, 4 to 9 times more likely to experience disability, depending on substance used, compared to those without either diagnosis.

LIMITATIONS: The study's cross-sectional design limits causal inferences.

CONCLUSIONS: Our research discovered that individuals who have both SUD and MDE are at a significantly higher risk of experiencing disability. This highlights the importance of integrating mental health and addiction services to mitigate the risk of disability and improve overall treatment outcomes.