Abstract
BACKGROUND: Anxiety is a prevalent mental health issue among junior high students, significantly impacting their physical and psychological well-being. This study aimed to investigate the developmental trajectory of anxiety in this population and its underlying causes and outcomes, providing support for adolescent mental health interventions. METHODS: A total of 1479 junior high students participated in a three-wave longitudinal study over two years. Latent Growth Curve Modeling was employed to examine the developmental trajectory of anxiety, and analyze the effects of gender and family functioning on the trajectory and the trajectory’s predictive role for Non-Suicidal Self-Injury (NSSI). Additionally, Latent Class Growth Modeling was used to explore heterogeneous subgroups within the anxiety trajectory. Multivariate logistic regression analyzed the predictive validity of gender and family functioning for trajectory class membership and the predictive effect of anxiety trajectory classes on NSSI. RESULTS: The overall anxiety trajectory exhibited a linear increasing trend. Female students showed higher initial anxiety levels and faster increases. Family functioning significantly negatively predicted anxiety levels. The anxiety trajectory predicted the occurrence of NSSI. Three distinct latent classes of anxiety trajectories were identified: High/Increasing, Moderate/Increasing, and Low/Decreasing. Gender and family functioning significantly predicted class membership. Individuals in the High/Increasing and Moderate/Increasing classes were more likely to engage in NSSI. CONCLUSIONS: Anxiety levels in junior high students show an overall linear increase. Gender and family functioning significantly influence the trajectory and predict subgroup membership. The anxiety trajectory predicts subsequent NSSI. Therefore, adolescent mental health interventions should address multiple factors and anxiety-specific risk profiles. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s40359-026-04287-x.