Background Eczema has been shown to be associated with an increased risk of depression. However, the effect of cigarette smoking on the association between eczema and depression remains unclear.
Objectives In this study, we investigated whether smoking behaviour and tobacco exposure influence the association between eczema and depression.
Methods This was a population-based cross-sectional study. Subjects (287 eczema patients and 40 patients with depression, out of a total of 2974 subjects in the database) were from the National Health and Nutrition Examination Survey 2005–2006, aged between 20 and 59 years. Lifetime presence of eczema was obtained by self-reporting questionnaires, and depression was assessed by the Patient Health Questionnaire. Smoking status was determined by self-report and serum cotinine levels. Univariate and multivariate logistic regressions were used to assess the association between eczema and depression with and without adjusting for smoking behaviour. Stratified analysis was also performed according to smoking status.
Results Eczema was significantly associated with depression (adjusted OR: 2.12; 95% CI: 1.59–2.83). This association persisted after additionally adjusting for smoking status. In stratified analysis, the association between eczema and depression was higher and stronger among current smokers than never smokers, former smokers and passive smokers.
Conclusion Our findings indicated that cigarette smoking may modify the risk of depression in eczema. We suggested cessation of smoking in eczema patients to decrease the risk of this psychiatric co-morbidity.