Trajectory of Non-suicidal Self-Injury among adolescents with borderline personality disorder over a 5-year period

Background: Engagement in Non-Suicidal Self-Injury (NSSI) is high among adolescents with borderline personality disorder (BPD), but the trajectory of NSSI in the transition period from adolescence to adulthood is unclear, and studies that look at predictors of persistence are highly needed. Methods: This study followed 111 adolescents aged 14–17 with BPD over a five-year period to observe the prevalence and predictors of NSSI. Information on NSSI was based on both self-report and clinician-administered interviews. Results: At the outset, 92.8% reported a history of NSSI, with an average of nearly five different types of NSSI. Despite this high initial prevalence, the rates of NSSI within the past two weeks decreased over time from 48% at baseline to 26% after one year, and further to 10% after two years. After five years, 37% reported engaging in NSSI within the past six months. Notably, all but one participant who reported NSSI after five years had engaged in NSSI already at baseline. The study identified that higher adolescent-rated but lower parent-rated BPD severity was associated with engagement in NSSI at baseline. Furthermore, ongoing NSSI after five years was predicted by lower parent-rated BPD severity and externalizing behaviors. Conclusions: NSSI is frequent in the early course of BPD, and persists in more than one-third after five years. Our findings highlight that baseline engagement in NSSI is a risk factor for persistence of NSSI in the transition period into early adulthood. Furthermore, the findings underscore the significance of integrating both adolescent and parent perspectives on BPD pathology in the assessment and management of NSSI.