Secondhand Smoking and Depressive Symptoms Among In-School Adolescents

International audienceIntroduction: Smoking has been linked with depressive symptoms in adolescents, but data on secondhand smoking and depressive symptoms in low- and middle-income countries are scarce. Thus, this study analyzes the association between secondhand smoking and depressive symptoms among in-school adolescents from 22 low- and middle-income countries. Methods: Data from the 2003–2008 Global School-Based Student Health Survey were analyzed in June 2019. Data on past-week exposure to secondhand smoke and past-year depressive symptoms were collected. The association between secondhand smoke and depressive symptoms was studied using multivariable logistic regressions and meta-analyses. Results: The sample consisted of 37,505 adolescents aged 12–15 years who never smoked. The prevalence of depressive symptoms increased from 23.0% in adolescents with no secondhand smoking to 28.9% in those with secondhand smoking every day in the past week. After adjusting for sex, age, food insecurity, and country, there was a dose–response relationship between secondhand smoking and depressive symptoms in the overall sample (0 days: reference; 1–2 days: OR=1.06, 95% CI=0.95, 1.18; 3–6 days: OR=1.38, 95% CI=1.20, 1.58; 7 days: OR=1.63, 95% CI=1.44, 1.86). The country-wise analysis showed that secondhand smoking on at least 3 days (versus <3 days) in the past week was associated with a 1.48-fold increase in the odds of depressive symptoms (95% CI=1.39, 1.59), with a low level of between-country heterogeneity (I2=4.2%). Conclusions: There was a positive association between secondhand smoking and depressive symptoms among in-school adolescents from low- and middle-income countries. Further research should investigate causality and assess whether prevention of exposure to secondhand smoke can have a positive effect on the mental well-being of adolescents