To explore the individual and joint effects of outdoor activities and different types of sedentary behavior on adolescent internalizing behaviors, so as to provide a basis for the prevention and intervention of such behaviors.

From July to December 2023, a stratified cluster random sampling method was used to select 1 691 primary and secondary school students in grades 5-12 from four primary and secondary schools in Baise City. Anonymous surveys were conducted by using the Outdoor Activities Questionnaire, Adolescent Sedentary Activity Questionnaire, and Youth Self-Report. The Chi-square test and Logistic regression analyses were used for statistical analysis.

The detection rate of internalizing behavior among adolescents was 13.13%, and the detection rate of internalizing behaviors in girls (15.53%) was significantly higher than that in boys (10.77%) (χ²=8.39, P < 0.01). Logistic regression analysis showed that outdoor activities ≥1 h/d (OR=0.56), screen-based entertainment sedentary behavior < 2 h/d (OR=0.58), and cultural sedentary behavior < 2 h/d (OR=0.55) significantly reduced the risk of internalizing behaviors (all P < 0.05). Logistic regression analysis of interaction effects revealed that the risks of internalizing behaviors were lower in the groups with "outdoor activities ≥1 h/d + screen-based entertainment sedentary behavior < 2 h/d" (OR=0.27) and "outdoor activities ≥1 h/d + cultural sedentary behavior < 2 h/d" (OR=0.30)(both P < 0.01).

Outdoor activities can mitigate the adverse effects of sedentary behaviors on adolescents' internalizing behaviors. Reducing screen time and leveraging the synergistic effects of "outdoor + cultural" activities may help reduce the risk of internalizing behaviors among primary and secondary school students.