1113Depressive symptoms and objectively measured physical activity and sedentary behaviour in adolescents

Background Physical activity and sedentary behaviour could be crucial risk factors for adolescent depression. This is the first study to use objective physical activity and sedentary behaviour measure to examine their association with depression in adolescents. Methods We analysed accelerometer data from population-based adolescents at ages 12, 14, and 16 and depressive symptoms at age 18. We used negative binomial regression and group-based trajectory models to analyse the data. Results We found that total physical activity decreased between 12 years and 16 years of age, driven by a decline in light activity and increase in sedentary behaviour. Each additional 60-minute increase in daily sedentary behaviour at ages 12, 14, and 16 was associated with an increased depression score at age 18 of 11·1% (95% CI, 5·1, 17·6), 8% (95% CI, 1·2, 15·2), and 10·5% (95% CI, 1·5, 20·8), respectively. Depression scores at age 18 were 9·6% (95% CI, 3·9, 15), 7.8% (95% CI, 0·8, 14.3), and 11·1% (95% CI, 2·6, 19.1) lower per additional 60-minutes of daily light activity time at ages 12, 14, and 16. These findings were robust to a series of sensitivity analyses. Conclusions Sedentary behaviour displaces light activity throughout adolescence and is associated with a higher risk of depressive symptoms at 18 years of age. Key messages Increasing light activity and decreasing sedentary behaviour during adolescence could be an important target for public health interventions aimed at reducing the prevalence of depression.