The effects of smoking habit change on the risk of depression–Analysis of data from the Korean National Health Insurance Service

•Never smokers and long-term quitters had a lower risk of depression than heavy continual smokers.•The risk of depression decreased when the amount of smoking decreased, although the difference was not statistically significant.•The influence of smoking habit change on depression seems to be prominent among people in their 50 s. We examined the effects of smoking habit change on the risk of depression using the National Health Insurance Service-National Health Screening Cohort database of Korea. This nationwide population-based cohort study included 88,931 men aged 40 years or older. The participants were divided into baseline heavy (≥20 cigarettes/day), moderate (10–19 cigarettes/day), and light (