Bidirectional Prospective Associations between Physical Activity and Depressive Symptoms. The TRAILS study
Purpose: Low levels of physical activity have been shown to be associated with depression in adults. The few studies that focused on adolescents yielded mixed and inconsistent results. Efforts to examine the direction of this relationship have been inconclusive up to now. The aims of this study were therefore to investigate (1) the direction of the inverse association between physical activity and depressive symptoms over time and (2) whether these associations are specific to particular clusters of depressive symptoms in adolescents. Methods: Depressive symptoms and physical activity were assessed in a population sample of adolescents (N=2230), who were measured at three waves between age 10 and age 17. Depressive symptoms were measured by the Affective Problems scale of the Youth Self-Report (YSR) and Child Behavior Checklist (CBCL), while physical activity was operationalized as the amount of time spent on physical exercise. Structural Equation Modeling was used to examine bidirectional effects of physical activity and depressive symptoms over time. Results: We found significant cross-lagged paths from prior physical activity to later depression as well as from prior depression to later physical activity (beta values= -.039 to -.047). After subdividing depression into affective and somatic symptoms, the affective symptoms were reciprocally related to physical activity, while the paths between somatic symptoms and physical activity did not reach statistical significance. Conclusions: An inverse bidirectional association between physical activity and general depressive symptoms was observed. This association was restricted to affective symptoms.