Reciprocal Within-Person Dynamics Between Internet Gaming Disorder Symptoms, Physical Activity, and Loneliness Among Chinese Adolescent Gamers: Three-Wave Prospective Cohort Study

BACKGROUND: Problematic gaming and internet gaming disorder (IGD) symptoms are prevalent in adolescence, yet the longitudinal interplay between physical activity (PA), loneliness, and IGD symptoms, as well as potential sexual differences, remains unclear. OBJECTIVE: This study aimed to examine reciprocal within-person associations between PA, loneliness, and IGD symptoms among Chinese adolescent gamers and test sexual differences in these associations. METHODS: We conducted a three-wave prospective cohort study among 1332 Chinese adolescents selected using convenience sampling from five middle schools in central China who had engaged in online gaming during the previous year (n=441, 33.1%, females; mean age 3.64, SD 0.76, years). PA, loneliness, and IGD symptoms were assessed using the Physical Activity Rating Scale-3, the three-item short form of the University of California, Los Angeles Loneliness Scale, and the nine-item Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition IGD Checklist, respectively, at three 6-month intervals: wave 1 (baseline, T1), wave 2 (T2), and wave 3 (T3). A random intercept (RI) cross-lagged panel model (CLPM) and multigroup analyses were conducted. RESULTS: RI-CLPM indicated that at the within-person level, higher PA predicted decreased subsequent loneliness (T1→T2: β=-0.12, 95% CI -0.16 to -0.08; T2→T3: β=-0.13, 95% CI -0.17 to -0.08) and IGD symptoms (T1→T2: β=-0.10, 95% CI -0.16 to -0.04, P=.009; T2→T3: β=-0.10, 95% CI -0.16 to -0.04). Increased loneliness (β=-0.22, 95% CI -0.26 to -0.18) and increased IGD symptoms (β=-0.08, 95% CI -0.12 to -0.04) each predicted later reductions in PA, indicating a mutually reinforcing cycle. Increased loneliness also predicted an increase in subsequent IGD symptoms (T1→T2: β=0.14, 95% CI 0.11-0.17), and increased IGD symptoms, in turn, predicted greater loneliness in the next wave (T1→T2: β=0.18, 95% CI 0.14-0.22). Multigroup models indicated that the protective effect of PA on later loneliness and the prospective effect of loneliness on subsequent IGD symptoms were stronger among girls than boys. In males, PA significantly predicted loneliness (β=-0.08 to -0.09, 95% CI -0.15 to -0.01), and loneliness significantly predicted IGD symptoms (β=0.09, 95% CI 0.03-0.15). In females, the cross-lagged effects from PA to loneliness were significant but stronger (β=-0.17, 95% CI -0.23 to -0.11), and the paths from loneliness to later IGD symptoms were also significant (β=0.16, 95% CI 0.11-0.21). CONCLUSIONS: PA, loneliness, and IGD symptoms are reciprocally linked in adolescent gamers. By using RI-CLPM to distinguish within-person changes from stable between-person differences, this study extends prior research based mainly on cross-sectional designs or traditional CLPMs and provides a clearer understanding of the dynamic interplay among behavioral, emotional, and gaming-related factors. The findings highlight that interventions aiming to prevent IGD symptoms should simultaneously promote PA and reduce loneliness, with particular attention to sex-specific patterns, especially in girls.