The Association between Smoking and Depression in a Canadian Community-Based Sample with Type 2 Diabetes

Abstract Objective To investigate the association between depression and smoking status within a community-based sample with type 2 diabetes mellitus, while controlling for socio-demographic, diabetes-related characteristics and complications, disability, other chronic illness and other health-related variables. Method A total of 1868 adults with type 2 diabetes were recruited via random digit dialing for the Montreal Health and Well Being Study (DHS). Smoking was classified as never, former, light (≤10 cigarettes a day) and moderate/heavy (11+ cigarettes a day). Depression was assessed using the Patient Health Questionnaire-9 and individuals were classified as no major depression vs. major depression syndrome. Logistic regression was used to test the association between major depression and smoking status, while controlling for other demographic and health-related variables. Results Major depression was associated with an increased likelihood of being a light or moderate/heavy smoker, having 2 or more diabetes complications, moderate–severe disability, and having 2 or more other chronic illnesses. In the fully adjusted model, having major dpression was associated with an increased likelihood of being a moderate/heavy smoker (odds ratio = 2.62, 95% confidence interval = 1.43–4.81). The association between light smoking and major depression was not significant when adjusting for confounding variables. Conclusions Smoking and depression are strongly associated in patients with type 2 diabetes, and this association appears to be strongest for moderate/heavy smokers. This finding has important clinical implications given that smoking cessation is an important health recommendation, and potentially means depression status may be an important consideration when targeting clients with diabetes who continue to smoke.