Depression is common and burdensome in adolescents. Understanding modifiable environmental risk factors is essential. There is evidence that physical activity is protective of depression. However, the impact of sedentary behavior (SB) on depression is relatively under-researched especially in low- and middle-income countries (LMICs). In this cross-sectional study, we explored the association between SB and depressive symptoms in adolescents from 30 LMICs, controlling for confounders including physical activity.

Data from the Global school-based Student Health Survey were analyzed in 67,077 adolescents [mean (SD) age 13.8 (0.9) years; 50.6% girls). Self-report measures assessed depressive symptoms during the past 12�months, and SB, which was a composite variable assessing time spent sitting and watching television, playing computer games, talking with friends during a typical day excluding the hours spent sitting at school and doing homework. Multivariable logistic regression analysis was conducted and a countrywide meta-analysis undertaken.

The prevalence of depressive symptoms and ≥�3�h/day of SB were 28.7 and 30.6%, respectively. There was a linear increase in the prevalence of depressive symptoms with increasing sedentary time beyond ≥3�h/day (vs. < 1�h/day). Among boys, 1–2�h/day of SB was associated with lower odds for depression (vs. < 1�h/day). Countrywide meta-analysis demonstrated that spending ≥3�h/day versus < 3�h/day was associated with a 20% increased odds for depressive symptoms (OR = 1.20; 95% CI = 1.16–1.24) with low between-country heterogeneity (I²�= 27.6%).

Our data indicate that being sedentary for ≥3�h/day is associated with increased odds for depressive symptoms in adolescence. Future longitudinal data are required to confirm/refute the findings to inform public interventions which aim to limit the time spent being sedentary in adolescents.