The Association between Smoking Cessation and Depressive Symptoms: Diet Quality Plays a Mediating Role

Objective: This cross-sectional study aimed to explore the association between smoking cessation and depressive symptoms and investigate the mediating role of dietary quality. Methods: We used data from the 2007–2014 National Health and Nutrition Examination Survey. Logistic regression models were applied to evaluate the associations between smoking cessation and depressive symptoms. Stratified analysis was performed according to different HEI levels. We examined the mediating role of HEI in the relationship between depressive symptoms and cessation duration using the Karlson–Holm–Breen (KHB) method. Results: A total of 20,004 participants aged 20 years or older were included in the analyses. There were significant correlations between years for smoking cessation and depressive symptoms (OR: 0.985, 95% CI: 0.971~0.999) after adjusting for correlation covariables. A likelihood ratio test showed that there was an interaction between smoking cessation and diet quality (p = 0.047). In the mediation analysis, we estimated that the increase in HEI scores after quitting smoking could explain the 6.91% decline in depressive symptoms. Conclusion: In this cross-sectional study, smoking cessation showed a protective effect on depressive symptoms and that diet quality can influence and mediate this association.