The study population for the trial included a total of 1,868 adults with type 2 diabetes. Smoking was assessed in the study with five different categories which included: never, former, light (≤10 cigarettes a day) and moderate/heavy (11+ cigarettes a day). Depression was assessed and categorized in the study using a Patient Health Questionnaire. Depression was classified in a binary fashion in this study and patients were recorded as either having no major depression or major depression syndrome. To make sense of the relationship between individual's smoking activity and the presence of depression a statistical analysis using a logistic regression was used, while controlling for other demographic and health-related variables.
After the procedures of the study were carried out, the results showed that major depression was indeed associated with an augmented likelihood of being a smoker in any of the categories (light (≤10 cigarettes a day) and moderate/heavy (11+ cigarettes a day)). Depression; however, was also increased in the patients having 2 or more diabetes complications, moderate-severe disability or having 2 or more other chronic illnesses. In the fully adjusted study model, having major depression was associated with an increased likelihood of being a moderate or heavy smoker (odds ratio = 2.62, 95% confidence interval = 1.43–4.81). The statistical analysis from the study also showed that the association between a light smoker and major depression was not significant when adjusting for confounding variables.
Researchers concluded that smoking and depression are strongly associated in patients with type 2 diabetes. The association between smoking and the presence of major depression syndrome was strongest for diabetic patients classified as either moderate or heavy smokers. These findings potentially mean that depression may be a significant consideration when targeting clients with diabetes who continue to smoke and optimal mental health may not be obtainable until smoking cessation is achieved.
Matthew Clyde, Geneviève Smith, Norbert Gariépy, et al. Canadian Journal of Diabetes. Association between Smoking and Depression in a Canadian Community-Based Sample with Type 2 Diabetes. Vol. 37, Issue 3, June 4, 2013