Developmental trajectories and dynamic associations between loneliness and non-suicidal self-injury in adolescents: the longitudinal mediating role of mobile phone dependence

This study aimed to examine the developmental trajectories and longitudinal associations among loneliness, non-suicidal self-injury (NSSI), and mobile phone dependence in adolescents. A three-wave longitudinal survey was conducted over three years, with approximately 12-month intervals. A total of 941 first-year junior high school students completed the Adolescent Non-suicidal Self-injury Assessment Questionnaire (ANSAQ), the UCLA Loneliness Scale (ULS-20), and the Mobile Phone Dependence Index (MPAI). Latent growth modeling (LGM), cross-lagged panel models (CLPM), and competing model comparisons were applied to analyze the data. LGM indicated a significant decline in adolescents’ loneliness over time (slope = − 0.32, p < 0.05), whereas the trajectory of NSSI remained relatively stable. Cross-lagged analyses revealed reciprocal longitudinal associations between loneliness and NSSI (T1 loneliness → T2 NSSI: β = 0.150, p < 0.001; T1 NSSI → T2 loneliness: β = 0.162, p < 0.001). The findings further suggested significant longitudinal associations among loneliness, mobile phone dependence, and NSSI. Mobile phone dependence was also longitudinally associated with the relationship between loneliness and NSSI. Loneliness and NSSI were reciprocally associated across adolescence. Mobile phone dependence may be longitudinally linked with this relationship, highlighting the importance of considering adolescents’ digital media use alongside emotional experiences when developing prevention and intervention strategies for adolescent psychological adjustment and self-injurious behaviors.