Joint associations between physical activity, screen time, and common mental disorders in Brazilian adolescents: Findings from ERICA

The prevalence of common mental disorders (CMD) is rising among young people, significantly impacting health. Physical activity (PA) is associated with reduced CMD, while increased screen time (ST) is associated with worsened symptoms. To analyze, the independent and joint associations of PA and ST with CMD. Additionally, we stratified the association between ST and CMD by levels of PA. We have used data from the Study of Cardiovascular Risks in Adolescents (ERICA). Adolescent’s PA (0, 1–59, 60–119, and ≥120 min/day) and ST (<2, 3–5, and ≥6h/day) was self-reported. CMD was measured using the 12-item General Health Questionnaire. Poisson regression models stratified by sex were used to examine associations. We analyzed data from 65,048 adolescents (mean=14.7 years). CMD prevalence was 16.9% (95%CI:16.2–17.6). Excessive ST (≥6h/day) was associated with CMD in girls (PR=1.61; 95%CI: 1.44–1.80) and boys (PR=1.40; 95%CI: 1.15–1.72). The PA-CMD association was J-shaped, with the greatest protection at 1–59min/week for girls and 60–119min/week for boys. A lack of PA combined with excessive ST increased CMD prevalence by 46% in girls and 72% in boys. The ST-CMD association was attenuated by PA levels only among boys. Excessive ST was associated with a higher CMD prevalence in both sexes, while PA’s protective effects varied by sex. The combined exposure to high ST and low PA further increased CMD, particularly among boys. This suggests that strategies promoting healthier movement behaviors and support adolescent mental health should consider sex-specific approaches. Due to the cross-sectional design, causal inference is not possible, highlighting the need for longitudinal studies. • Physical activity (PA) showed a sex-specific association with CMD in adolescents • High screen time (ST) raised common mental disorders (CMD) in both sexes • Joint association of low PA and high ST increased CMD by 46% in girls and 72% in boys • The association of ST with CMD was attenuated by PA levels only among boys