Prevalence and School-Related Factors Associated With Depression and Self-Harm in Children Aged 9 to 10 Years

Background Depression and self-harm in preadolescent children are significant public health concerns but remain understudied, especially within the context of China's unique socioeducational environment. This study aimed to determine the prevalence of depression and self-harm among children aged 9–10 years in China and identify associated school-related risk factors. Methods A large-scale cross-sectional study was conducted from September to December 2020 in Chongqing, China. A total of 22,266 children in grades 3–5 completed an online questionnaire. Depression symptoms were assessed using the Children’s Depression Inventory (CDI), with a cutoff score of ≥ 19 indicating clinical significance. Self-harm was measured by a single self-report item. Sociodemographic and school-related factors (peer relationships, bullying, academic pressure, smartphone use) were also evaluated. Multivariable logistic regression analyses were performed to identify factors associated with depression and self-harm. Results The prevalence of depression and self-harm was 16.2% and 13.3%, respectively. Multivariate analyses revealed several significant factors. For depression, the strongest predictors were poor peer relationships (OR = 11.61, 95%CI = 8.90–15.15 for "general" relationships), high academic pressure (OR = 7.01, 95%CI = 6.13–8.03), and self-harm (OR = 4.39, 95%CI = 3.99–4.84). Males had a higher risk than females (OR = 1.33, 95%CI = 1.22–1.45), and rural residence was associated with increased odds (OR = 1.33, 95%CI = 1.19–1.48). For self-harm, the primary predictor was depression (OR = 4.37, 95%CI = 3.97–4.82), followed by high academic pressure (OR = 2.52, 95%CI = 2.19–2.90) and frequent bullying exposure (e.g., OR = 1.77 for frequent bullying, 95%CI = 1.55–2.02). Problematic smartphone use was also significantly associated with both outcomes. Conclusions This study reveals a high prevalence of depression and self-harm among Chinese preadolescents. Modifiable school-related factors, including poor peer relationships, academic pressure, bullying, and digital use, are strongly associated with these mental health difficulties. The findings underscore the urgent need for integrated, school-based interventions that focus on improving the psychosocial environment, mitigating academic stress, and promoting healthy digital habits to support the mental well-being of children.