Abstract
BACKGROUND: Adolescent mental health has emerged as a critical public health issue, with increasing prevalence of anxiety and depression. Physical activity (PA) is known to offer numerous health benefits, but its relationship with adolescent mental health is less clear and the optimal intensity and duration remain debated. METHODS: This prospective cohort study analyzed data from 6,991 adolescents in Jiangsu, China. Mental health was assessed using the Strengths and Difficulties Questionnaire (SDQ), and PA was categorized as moderate-intensity PA (MPA) or vigorous-intensity PA (VPA) based on self-reported activity levels. The study examined the cross-sectional and longitudinal associations between PA and mental health, adjusting for various confounding factors. RESULTS: Among the cohort (mean age, 12.71 ± 2.12 years; 53.6% male), 1,265 participants (18.1%) had mental health issues at baseline. Cross-sectional analyses revealed a significant negative non-linear dose-response association between levels of MPA and VPA and the prevalence of mental health problems in adolescents (P = 0.001), after adjusting for potential confounding factors such as age, gender, nationality, and family structure. Specifically, adolescents who engaged in 30-59 min of MPA daily exhibited a 56.4% reduction in the odds ratios of mental health issues (OR = 0.436, 95% CI: 0.327-0.581, P < 0.001). Similarly, those who participated in up to 29 min of VPA daily had 49.2% lower odds ratios (OR = 0.508, 95% CI: 0.415-0.622, P < 0.001). Longitudinal analyses confirmed that MPA and VPA were significantly negatively associated with the incidence of subsequent mental health problems. In particular, adolescents who engaged in 30-59 min of MPA daily (OR = 0.548, 95% CI: 0.411-0.729, P < 0.001) and up to 29 min of VPA daily (OR = 0.583, 95% CI: 0.474-0.716, P < 0.001) demonstrated the strongest protective effects. Sensitivity analyses and subgroup analyses also confirmed the robustness of these results. CONCLUSIONS: Significant positive associations exist between moderate PA and improved adolescent mental health outcomes. The better effects are observed with 30-59 min of MPA or ≤ 29 min of VPA daily. Exceeding these durations may not yield additional benefits. When promoting PA among adolescents, focus should be placed on selecting appropriate activity types and scientifically managing activity duration.