Abstract
Physical activity (PA) has been identified as a protective factor for adolescent mental health. This study analysed the association between PA and levels of anxiety, depression, and stress among adolescents, considering gender, educational stage, and type of sport. A cross-sectional design was conducted with 106 Spanish secondary school students aged 12-16 years. Data were collected through a self-reported questionnaire on PA participation and the validated DASS-21 scale. Descriptive statistics, chi-square (χ(2)) tests, and adjusted residual analyses were performed. The results showed a significant negative association between PA and anxiety (χ(2) = 303.34, p < 0.01), stress (χ(2) = 310.64, p < 0.01), and depression (χ(2) = 324.32, p < 0.01). Non-athletes presented higher levels of psychological problems compared with active peers, while girls and older students showed greater vulnerability. Adolescents involved in team sports exhibited lower anxiety and stress than those participating in individual sports. In conclusion, higher participation in physical activity, particularly team-based disciplines, is associated with better mental health in adolescents. These findings reinforce the importance of integrating regular physical activity into school contexts to support psychological well-being during adolescence.