Abstract
Participation in regular physical activity (PA) is associated with numerous health benefits, including improvement in adolescents' mental health. The current study aimed to assess the effects of a 12-week physical activity intervention on psychological symptoms of adolescents. The sample of this controlled randomized study was composed by 150 adolescents aged 12 to 15 years old. PA intervention is an adaptation of the ActTeens Program, which includes structured PA sessions delivered during Physical Education classes. The Strengths and Difficulties Questionnaire (SDQ) was used to measure psychological symptoms. To analyze the effects of the intervention on psychological symptoms, generalized estimating equations (GEEs) models were constructed. After 12 weeks, there were no significant intervention effects for emotional problems (mean difference: -0.14; 95% IC: -1.1-0.82), conduct problems (mean difference: 0.14; 95% IC: -0.6-0.8), attention deficit/hyperactivity disorder (mean difference: -0.66; 95% IC: -1.4-0.1), peer problems (mean difference: 0.2; 95% IC: -0.6-1.0), prosocial behavior (mean difference: 0.00; 95% IC: -0.8; 0.8) and overall mental health score (mean difference: 0.15; 95% IC: -2.0; 2.3). No improvement in psychological symptoms was observed after 12 weeks of PA intervention. Future studies should explore how PA in different dimensions and contexts may impact positively on adolescents' mental health.