Background: Epidemiological evidence on the relationship between smoking and secondhand smoke (SHS) exposure and depressive symptoms during pregnancy has been limited. The present cross-sectional study examined this issue in Japan.
Methods: Between April 2007 and March 2008, 1757 pregnant women who lived in one of seven prefectures on Kyushu Island in southern Japan or in Okinawa Prefecture, an island chain in the southwest of Japan, participated in the Kyushu Okinawa Maternal and Child Health Study, a prebirth cohort study. In the present study, data on 1745 pregnant women were available for analysis. Information on smoking, SHS exposure, depressive symptoms, and potential confounding factors was obtained through a self-administered questionnaire. Depressive symptoms were defined as present when subjects had a Center for Epidemiologic Studies Depression Scale score of 16 or higher. Adjustment was made for age, gestation, region of residence, number of children, family structure, household income, education, job type, history of depression, and family history of depression.
Results: The prevalence of depressive symptoms during pregnancy was 19.2%. Compared with having never smoked, both former and current smoking was independently associated with a higher prevalence of depressive symptoms during pregnancy: the adjusted odds ratios (ORs) were 1.39 (95% CI: 1.06-1.83) and 2.49 (95% CI: 1.36-4.45), respectively. Also, 3.0 to 7.9 and 8.0 or more pack-years of smoking were independently positively related to depressive symptoms during pregnancy: the adjusted ORs were 1.55 (95% CI: 1.08-2.22) and 1.97 (95% CI: 1.26-3.03), respectively (P for trend = 0.0005). Among the 1183 subjects who had never smoked, current SHS exposure at home was independently positively associated with depressive symptoms during pregnancy: the adjusted OR was 1.51 (95% CI: 1.003-2.30).
Conclusions: Former and current smoking, 3.0 or more pack-years of smoking, and current SHS exposure at home may be positively associated with depressive symptoms during pregnancy.