[Dose-dependent associations between screen time, contents and adolescents' mental health]

Objective: To investigate the relationship between screen time and content, and the mental health status of adolescents. The findings will inform the formulation of targeted intervention policies to enhance adolescent mental health. Methods: Between September and November 2023, 5 197 students from 64 junior high, senior high, and vocational schools across 13 districts in Wuhan were recruited, using the stratified whole-cluster random sampling to investigate their screen behavior and mental health status. Mental health status was measured using the Mental Health Inventory for Chinese Middle School Students (MMHI-60). A generalized additive model was used to explore the nonlinear association between screen time and mental health status. Additionally, a mixed-effects model was utilized to explore the dose-response associations between average daily total screen time, screen time for different content types, and adolescents' mental health status and the impact of the proportion of different screen contents on mental health outcomes. Results: The age of the participants was (14.40±1.48) years, with 56.07% being boys. The MMHI-60 score averaged 1.73±0.70. The M(Q₁,Q₃) for daily total screen time was 50.00 (0.00,128.57) minutes. The M(Q₁,Q₃) for screen time dedicated to gaming, studying, socializing, and watching videos were 0.00 (0.00, 20.00), 8.57 (1.64, 44.50), 4.28 (0.00, 30.00), and 0.00 (0.00, 25.71) minutes, respectively. A non-linear association was observed between average daily screen time and adolescent mental health problem score, 0-1 hour of daily screen time was beneficial for adolescent mental, compared to no screen time. However, screen time exceeding 1 hour was detrimental, with the negative impact increasing alongside screen time duration. When total daily screen time was held constant, the proportion of time spent on gaming (β=0.14, 95%CI: 0.05-0.23,P=0.003) and video (β=0.21, 95%CI: 0.09-0.28, P<0.001) was positively correlated with mental health problems, whereas the proportion of time spent on studying was negatively correlated with mental health problems (β=-0.17, 95%CI: -0.24 - -0.11, P<0.001). Conclusions: Moderate screen time is advantageous for adolescent mental health. However, it is crucial to minimize the proportion of screen time dedicated to video and gaming activities to mitigate potential adverse effects.