Total and domain‑specific sedentary time in relation to internalizing problems in Chinese adolescents: a cross‑sectional study

Abstract Background Internalizing problems—depression, anxiety, emotional distress, and social withdrawal—are prevalent among adolescents, with a pooled prevalence of depressive symptoms exceeding 26% in Chinese youth. While sedentary behavior is consistently linked to these issues, evidence is limited on whether this link varies across behavioral domains or follows a non-linear pattern. This study examined the non-linear association between total sedentary time and internalizing problems, and quantified the independent and mutually adjusted associations of four specific sedentary behavior types. Methods This cross-sectional study included 2,360 primary and secondary school students from Baise, Guangxi, using multi-stage stratified cluster sampling. Internalizing problems were assessed via the Chinese Youth Self-Report (YSR). Sedentary time was measured using a validated questionnaire and categorized into four types: recreational screen-based, educational, cultural, and social/entertainment. Covariates included sex, age, ethnicity, BMI, moderate-to-vigorous physical activity (MVPA), and parental education. Data were analyzed using descriptive statistics, restricted cubic splines, and multiple linear regression. Results Mean total sedentary time was 7.0 h/day, with the four types averaging 5.3, 4.5, 3.3, and 2.2 h/day, respectively. All four types were positively intercorrelated (all P < 0.001). Restricted cubic spline analysis revealed a suggestive J-shaped visual pattern for total sedentary time ( P for non-linearity = 0.086), with the lowest internalizing score at ~ 4.0 h/day. Recreational screen-based time showed a monotonic increase ( P = 0.055); educational time followed a U-shaped curve ( P = 0.030), nadir at ~ 2.0 h/day; cultural time showed no non-linear association ( P = 0.742); social/entertainment time showed an initial decline then increase ( P = 0.053), nadir at ~ 1.5 h/day. In separate analyses, all four types were positively associated with internalizing problems ( β = 0.580–0.612, all P < 0.01). After mutual adjustment, recreational screen-based ( β = 0.520, P < 0.001) and cultural ( β = 0.356, P = 0.004) time remained significant; social/entertainment time attenuated to non-significance ( β = 0.165, P = 0.291); educational time reversed direction and was non-significant ( β = − 0.028, P = 0.817). Conclusions Total sedentary time showed a suggestive J-shaped visual pattern with internalizing problems, with an observed inflection point at ~ 4.0 h/day. Associations varied by type, with recreational screen-based time showing the most robust positive association. Interventions should prioritize reducing recreational screen-based sedentary time, while also considering the potential benefits and risks of educational and cultural sedentary time. These findings highlight the importance of domain-specific approaches to sedentary behavior reduction in adolescent mental health promotion.