Longitudinal trajectories of depressive symptoms in adolescent students

BACKGROUND: Longitudinal studies examining depressive symptom trajectories in adolescents remain limited, particularly in school-based populations. This study aimed to identify psychosocial risk and protective factors associated with depressive symptom trajectories in a cohort of Chinese adolescents. METHODS: A four-semester longitudinal survey was conducted among 1,145 primary and secondary school students using the 9-item Patient Health Questionnaire (PHQ-9) and the Mental Health Diagnostic Test Scale (MHT). Quasi-Poisson generalized linear models adjusted for overdispersion in PHQ-9 scores. Latent class mixed models delineated distinct depressive symptom trajectories. Binary logistic regression evaluated predictors of high-risk group membership, and generalized linear mixed-effects models assessed time-by-group interactions, adjusting for age, sex, and grade. RESULTS: Across four time points, 27.9%-32.2% of adolescents scored ≥ 5 on the PHQ-9, indicating elevated risk for depression. Learning anxiety was the most prevalent anxiety subtype (41.9%-49.1%). Significant risk factors associated with higher depressive symptom scores included learning anxiety, hopelessness, interpersonal anxiety, sensitiveness, impulsive tendency, and temper loss, whereas family warmth and help-seeking behavior served as protective. Depressive symptoms in the past year were strong predictors of current depressive symptom severity. Two distinct depressive symptom trajectories were identified: a stable low-risk group and a high-risk group with worsening symptoms. The high-risk group, particularly among sixth-grade students, exhibited a sharper increase in loneliness over time, with hopelessness and somatic anxiety as key predictors. CONCLUSIONS: This study delineates the developmental trajectories of depressive symptoms in adolescents and identifies modifiable psychosocial factors associated with high-risk patterns. The findings underscore the importance of early identification and targeted, school-based interventions to improve adolescent mental health outcomes.