Research paperMajor depression and non-specific distress following smoking cessation in the Canadian general population

- Major depressive episode prevalence and non-specific distress improve after successful smoking cessation.
- The improvement is gradual, over about one year.
- People who smoke can be reassured that smoking, cessation will likely improve their mental health in the longer term.

BackgroundOutcome data from smoking cessation trials indicate that improvement in mental health occurs after smoking cessation. This suggests that smoking cessation should be a priority for mental health services. However, participants in such trials may not be representative of the general population. This study investigates changes in mental health following smoking cessation in a set of general population samples.MethodsData from a library of cross-sectional surveys conducted by Statistics Canada between 2001 and 2013 were included in this analysis. Survey estimates were pooled in order to increase precision. Associations between smoking (and smoking cessation), major depressive episodes (MDE) and non-specific distress (assessed using the K-6 scale) were evaluated using meta-analysis and meta-regression techniques.ResultsThe annual prevalence of major depression was higher in daily (11.0%) than in never smokers (4.4%). The prevalence in former daily smokers was 5.1%. The prevalence of MDE and distress was elevated in those recently quitting but returned to baseline levels within one year.ConclusionsAfter smoking cessation, indicators of mental health improve over time, especially in the first year. The findings support the idea that smoking cessation should be a part of the management of common mood and anxiety disorders. However, due to its observational nature this study in itself cannot confirm causality, sustained abstinence may be an effect of improved mental health rather than its cause.LimitationsThe cross-sectional nature of the constituent surveys does not allow causal inference. No biological measures (e.g. cotinine) were available.