TY - EJOU AU - Yang, Liu AU - Zhang, Qingru AU - Yan, Jin TI - Dose-Response Associations between Physical Activity and Poor Mental Health among High-School Students: Sleep Duration as a Potential Mediator T2 - International Journal of Mental Health Promotion PY - VL - IS - SN - 2049-8543 AB - Backgrounds: This study examined whether sleep duration may potentially mediate the association between moderate-to-vigorous physical activity (MVPA) and mental health between in a nationally representative sample of U.S. high school students. Methods: Data from 15,671 U.S. high school students participating in the 2023 Youth Risk Behavior Survey (YRBS) were analyzed. MVPA was measured as weekly days achieving at least 60 min of activity, and frequent poor mental health was defined as reporting poor mental health most of the time or always during the past 30 days. Sleep duration was evaluated as a mediator. Survey-weighted regression and Karlson–Holm–Breen mediation analyses were performed, adjusting for relevant sociodemographic and health-related covariates. Results: Each additional day of MVPA was associated with a 7.5% lower odds of frequent self-reported poor mental health (OR = 0.925, 95% CI: 0.898–0.954), while each additional hour of sleep was associated with a 29.0% lower odds (OR = 0.710, 95% CI: 0.668–0.756). KHB mediation analysis indicated that sleep duration emerged as a potential mediator of this association. The total association between MVPA and frequent poor mental health was β = −0.048 (95% CI: −0.072 to −0.025), with an indirect effect through sleep duration of β = −0.025 (95% CI: −0.031 to −0.019), accounting for 52.0% of the observed association. The proportion of the association accounted for by sleep duration was higher in females (55.68%) than in males (44.22%). Conclusions: More frequent achievement of the 60-min PA guideline was associated with lower odds of frequent poor mental health among U.S. high school students. Sleep duration accounted for approximately one-half of this observed association, supporting its potential role in the relationship between physical activity and mental health. Strategies that promote both regular physical activity and adequate sleep may help improve adolescent mental health. KW - Physical activity; mental health; sleep duration; adolescents; mediation; YRBS DO - 10.32604/ijmhp.2026.083872