From hurt to harm: how types of childhood maltreatment shape the trajectories of non-suicidal self-injury through developments in depressive symptoms and peer victimization.

Childhood maltreatment commonly predicts adolescent non-suicidal self-injury (NSSI). However, evidence on how specific maltreatment subtypes influence NSSI trajectories (i.e., intercept and slope) and through which potential pathways remain limited. Moreover, gender differences in these associations are insufficiently understood. Using latent growth curve model (LGCM) and its extensions, this study examined the effects of distinct maltreatment subtypes on adolescent NSSI trajectories, tested the mediating roles of depressive symptoms and peer victimization, and assessed whether these indirect associations vary by gender. A total of 3,228 Chinese adolescents (Mage = 13.10 years, SD = 0.83; 58.1% boys) completed three-wave assessments. Results indicated: (1) higher levels of childhood emotional abuse, emotional neglect, and physical abuse predicted higher initial levels of NSSI (intercept), and greater emotional abuse further predicted a less steep increase in NSSI over time (slope); (2) childhood emotional abuse and emotional neglect indirectly affected the intercept of NSSI via the intercepts of depressive symptoms and peer victimization across the total, boys', and girls' samples, whereas only emotional abuse indirectly influenced the slope of NSSI via the slopes of these two mediators in the total and boys' samples; (3) childhood physical abuse influenced the intercept of NSSI through the same dual pathways in the total and boys' samples, whereas childhood physical neglect affected the slope of NSSI via the slope of peer victimization among boys. These findings underscore the need for personalized interventions tailored to specific maltreatment types and their potential pathways, with attention to gender differences.