Physical activity and mental health in children and adolescents during and after the COVID-19 pandemic: findings from the six-wave German COPSY study

Background: The COVID-19 pandemic coincided with declines in youth mental health and health-related quality of life. Physical activity (PA) has been identified as a modifiable factor associated with better mental health outcomes, yet longitudinal evidence jointly examining well-being and mental health problems remains limited. Methods: = 1,819) surveyed during and after the COVID-19 pandemic. PA (self-reported days/week ≥60 min) was categorized as low (0-2 days), medium (3-5), high (6-7). Outcomes were health-related quality of life (KIDSCREEN-10, parent-report) and mental health problems (SDQ, parent-report). Linear mixed models with random intercepts and slopes included PA, time, age, gender, socioeconomic status, and current mental disorder. Two-way interactions between PA and covariates were tested, and sensitivity analyses used a WHO guideline indicator (≥60 min/day). Results: Higher PA was dose-responsively associated with better health-related quality of life and fewer mental health problems across all waves. Compared to low PA, higher PA levels related to small to moderate improvements in health-related quality of life and small reductions in mental health problems. A small interaction indicated that the association between high PA and fewer mental health problems was slightly stronger among older adolescents; all other interactions were non-significant. Sensitivity analyses yielded comparable results. Conclusions: PA showed small to moderate associations with higher health-related quality of life and fewer mental health problems during and after the pandemic. Ensuring accessible opportunities for youth PA should be integral to mental health promotion and future crisis preparedness.