The impact of bullying victimization on non-suicidal self-injury in adolescents: the mediating role of rumination and the moderating role of friendship quality

Non-suicidal self-injury (NSSI) is a prevalent global public health concern among adolescents, with bullying victimization recognized as a key risk factor, while the underlying cognitive mechanisms and interpersonal protective factors remain understudied. This study aimed to investigate (1) the relationship between bullying victimization and non-suicidal self-injury (NSSI) in adolescents, (2) the mediating role of rumination in the association between bullying victimization and NSSI, and (3) the moderating role of friendship quality in the relationship between rumination and NSSI. A sample of 692 adolescents was assessed using the Bullying Victimization Questionnaire, the Adolescent NSSI Behavior Assessment Questionnaire, the Ruminative Responses Scale (RRS), and the Friendship Quality Questionnaire (FQQ). Results indicated that: (1) Bullying victimization exerted a significant positive predictive effect on NSSI (explaining 59.85% of the variance); (2) Rumination partially mediated the link between bullying victimization and NSSI, accounting for 40.15% of the total effect; (3) Friendship quality moderated the relationship between rumination and NSSI (<i>β</i> = -0.002, <i>p</i> < 0.001), attenuating the detrimental impact of rumination on NSSI. These findings collectively suggest that bullying victimization, rumination, and lower friendship quality collectively heighten adolescents' risk of engaging in NSSI.