Active smoking and exposure to secondhand smoke and their relationship to depressive symptoms in the Korea national health and nutrition examination survey (KNHANES)

BACKGROUND: The relationship between tobacco smoking, including secondhand smoking, and depression has been assessed. The purpose of this study was to evaluate the association between secondhand smoking among current, former and never smokers and depressive symptoms. For secondhand smoking, gender differences and sources of exposure were examined. METHODS: Data from 34,693 participants from the fourth and fifth Korean Health and Nutritional Examination Survey (2007–2012) were analyzed in 2014. Self-reported exposure to active (current, former or never) and secondhand smoking and depressive symptoms experienced during the past year were analyzed using logistic regression. The dose–response relationship between duration of secondhand smoke exposure and depression was assessed with stratification by gender and sources of exposure (at home only, at the workplace only or both). RESULTS: Regardless of their smoking status, all women who had secondhand smoke exposure at home reported more depressive symptoms than non-smoking women without any exposure to secondhand cigarette smoking (OR 1.43, 95 % CI 1.04–1.96 for current smokers; OR 2.32, 95 % CI 1.04–5.16 for former smokers; OR 1.25, 95 % CI 1.08–1.43 for never smokers). There was also a significant dose–response pattern (p-trend <0.001) for the duration of secondhand smoke exposure at home among women. No significant association was found between smoking and depressive symptoms in men. CONCLUSIONS: There was a significant association between secondhand smoke exposure at home and depressive symptoms in women. Secondhand smoke exposure at home was associated with depressive symptoms in a dose–response manner. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12889-015-2402-1) contains supplementary material, which is available to authorized users.