Physical activity partially mediating the social gradient in adolescent mental health.

Objectives: To examine whether there is a socioeconomic status (SES) gradient in adolescent mental health problems, and if so, whether out-of-school physical activity mediates this gradient. Methods: Based on data from 1,285 adolescents in Sweden, we used linear regression analysis to examine whether the social gradient in mental health problems (stress and psychosomatic symptoms by survey) varied by SES indicators, including income, father's and mother's education (register data). Parameter estimates were obtained using ordinary least squares. We also investigated if out-of-school physical activity (accelerometer data) mediates these gradients by applying the potential outcomes framework for mediation analysis. This framework accounts for potential exposure-mediator interaction, and confidence intervals were calculated using bootstrapping. Results: Gradients in adolescents' mental health problems were observed for all SES indicators, the coefficient of determination R Conclusion: There are social gradients in adolescents' mental health problems based on income and parents' education, and these gradients appear to be partially mediated via out-of-school VPA and MVPA, predominantly among females.