Sex-Specific Co-developmental Trajectories of Problematic Internet Use and Aggression Among Adolescents: Associations With Mental Health

Although existing studies have separately documented the heterogeneous development of Problematic internet use (PIU) and aggression and identified sex differences, little is known about their sex-specific co-developmental patterns among Chinese adolescents. Even less is known about how these patterns are linked to changes in mental health over time. Therefore, this study aims to (a) examine the sex-specific co-developmental trajectories of PIU and aggression, (b) examine whether baseline mental health predicts membership in different joint trajectory classes, and (c) examine whether these trajectory classes are differentially associated with subsequent mental health outcomes. This longitudinal study collected data from 1,531 Chinese junior middle school students (age: M = 12.30 years, SD = 0.55, range = 11–15 years, 51.05% girls) at three points at 6-month intervals. PP-LCGM models revealed three trajectories for boys (i.e., average , congruent-low , and moderate-increasing ) and four trajectories for girls (i.e., low-increasing , moderate-increasing PIU and moderate-stable aggression , congruent-low , moderate-stable PIU and moderate-decreasing aggression ). Further analyses indicated that mental health exhibited stronger predictive effects in the girls subgroup than in the boys subgroup, with significant variations in mental health outcomes observed within both subgroups. Findings highlight the importance of prioritizing prevention and intervention efforts for high-risk subgroups.