The social gradient in adolescent mental health problems and the role of physical activity

BACKGROUND: In Sweden, the share of 13 and 15-year-old students reporting ≥ 2 psychosomatic symptoms (PSS) more than once a week doubled between 1985/1986 and 2017/2018, during which there were increases in both income inequalities and adolescents with insufficient physical activity (PA). PA during non-school time has been shown to be negatively associated with stress and PSS among adolescents. We aimed to explore whether there is a socioeconomic status (SES)-related gradient in adolescent mental health problems, and if so, whether non-school sedentary time (SED) and PA mediate this social gradient. METHODS: We used data from STARS, a prospective and observational cohort study of 2283 7th grade students in Västra Götaland, Sweden. A total of 1235 participants (mean age 13.6±0.394 years, 59% females) returned with valid accelerometer data (≥ 10 hours per day for ≥ 4 days), answered questionnaires regarding stress and PSS, and had parents’ earned income registry data. Ordinary least square for linear regressions and bootstrapping for mediation analysis were used with 95% CI, repeated for males and females separately. RESULTS: We found that higher income was associated (α = 5%) with less stress (-0.1108, p ≤ 0.001 and PSS (-0.1315, p ≤ 0.001). For stress, we found that non-school PA partly mediated this association. This was true for light PA (LPA) (-0.0040, [-0.0093-0.0003]), moderate to vigorous PA (MVPA) (-0.0077, [-0.0152-0.0023]) and vigorous PA (VPA) (-0.0090, [-0.0166, -0.0031]). When separated by sex, mediation via PA was found only in females. For PSS, mediation effect was found for MVPA (-0.0071, [-0.0137, -0.0018]) and VPA (-0.0103, [-0.0182, -0.0039]), but not when separated by sex. CONCLUSIONS: There is a social gradient in both stress and psychosomatic symptoms among adolescents, mediated by physical activity although to a relatively small part. This shows the relevance to inform policy on the need to enable extracurricular sports activities for adolescents. KEY MESSAGES: • Physical activity partly explains the social gradient in adolescent mental health. • Supporting extracurricular sports activities may help to reduce the social gradient in adolescent mental health.