Association of smoking cessation duration and e-cigarette switching with mental health: A cross-sectional study in Korea

Background Although the adverse mental health effects of cigarette smoking are well documented, how these risks change over time following cessation remains unclear. With the growing adoption of electronic cigarettes (e-cigarettes), many smokers now switch to e-cigarettes instead of quitting entirely, yet the mental health implications of this transition are poorly understood. Methods This cross-sectional study analyzed data from 218,921 Korean adults in the 2024 Korea Community Health Survey. Smoking status was classified as never smokers, quitters, e-cigarette switchers, combustible cigarette–only users, e-cigarette–only users, and dual users. Mental health outcomes included depression, suicidal ideation, and poor sleep quality. Survey-weighted multivariable logistic regression models were used to assess the associations of smoking status and years since quitting with each mental health outcome. Results Among 218,921 participants, 3.5 % had depression, 1.2 % reported suicidal ideation, and 42.8 % had poor sleep quality. Compared with never smokers, quitters had significantly higher odds of depression, suicidal ideation, and poor sleep quality. E-cigarette switchers also showed elevated odds across all three outcomes. Among quitters, the odds of adverse mental health outcomes demonstrated a clear decreasing trend with longer cessation duration, whereas e-cigarette switchers showed an increasing trend in the odds of suicidal ideation with longer cessation duration. Conclusions Combustible cigarette smoking and e-cigarette use were associated with increased odds of adverse mental health outcomes. Sustained smoking cessation was associated with progressively lower odds of depression, suicidal ideation, and poor sleep quality. In contrast, e-cigarette switchers showed no clear duration-related trend.