This study explored the growth of non-suicidal self-injury (NSSI) frequency over 2.5 years in a clinical sample of adolescent girls. Following a functional model of NSSI, the contribution of emotion dysregulation, peer victimization, and psychological maladjustment were evaluated as the predictors of NSSI trajectories. Participants of 99 girls (Mage = 16.03 years) were admitted for psychiatric hospitalization, who responded to questionnaires assessing NSSI, emotion dysregulation, relational and overt peer victimization, and internalizing and externalizing symptoms. NSSI was also assessed at 6 months and 2.5 years following the baseline assessment. Linear mixed modeling estimated NSSI frequency over time. The findings highlight the stable nature of NSSI and the contribution of emotion dysregulation and internalizing symptoms to NSSI patterns. Peer victimization and externalizing behavior problems were not the significant predictors. Developing interventions targeting these NSSI predictors early in girls' development may prevent the emergence and maintenance of NSSI.
Keywords: Non-suicidal self-injury; emotion dysregulation; internalizing symptoms; self-harm.