Seasonal biological social and cognitive mechanisms of mental health among Chinese adolescents.

This study develops a "Bio-Social-Cognitive Dynamic Interaction Model" to explore seasonal mental health risks in Chinese adolescents. Using data from cross-sectional surveys (N = 6,121), longitudinal tracking (N = 1,000), and RCTs (N = 200), we assess mental health via PHQ-9, GAD-7, and SADQ scales. We analyze multidimensional indicators (melatonin, vitamin D, academic stress) via SEM and ARIMA, considering school stage and gender. Results show winter has the highest depression and anxiety scores (PHQ-9: M = 14.5 ± 4.8), linked to vitamin D deficiency (β=-0.25, p < 0.001) and social stress. Spring academic stress affects emotional stability via melatonin and sleep issues (β = 0.15, p = 0.002), while summer anxiety is tied to social overload and body dissatisfaction (β = 0.10, p = 0.04). Winter light therapy increases vitamin D (Δ = 8.2 ng/mL, p < 0.001) and reduces depression (ΔPHQ-9=-3.1, p = 0.005). We recommend seasonal interventions like winter light therapy, flexible spring exams, and summer social media literacy programs, and emphasize year-round monitoring for effective risk mitigation.