Longitudinal course of repetitive adolescent non-suicidal self-injury: Psychological functioning among adults who have ceased or continued to self-injure.

Résumé

Non-suicidal self-injury (NSSI) often emerges in adolescence, but the lack of longitudinal research means it remains unclear whether the risk of poor outcomes in adulthood reflects NSSI engagement specifically or broader adolescent vulnerabilities, and what predicts NSSI cessation among adults. This study addresses these gaps using data from a Swedish school cohort collected in 2007-2008 (N = 506-522, M = 13.7-14.7), 2017 (N = 375, M = 25.3), and 2023 (N = 252, M = 29.8). Participants were grouped as having reported repetitive NSSI in adolescence (≥5 instances in 2007/2008), and as having ceased (0 instances) or continued (≥1 instance) NSSI by 2017/2023, or as having never reported any NSSI. Both NSSI cessation and NSSI continuation were associated with poorer outcomes than never having reported NSSI. However, for the cessation group, all differences except self-views were explained by adolescent mental health. Relative to continued NSSI, cessation was associated with higher flourishing and lower depression, stress, emotion dysregulation, and self-hatred (∆EMM = 0.43-1.00, p = 0.017), independent of adolescent mental health. Continuation between ages 25 and 30 was predicted by lower flourishing (OR = 0.46, p = 0.018) and higher emotion dysregulation, self-inadequacy, and self-hatred (OR = 1.93-2.27, p ≤ 0.037). In conclusion, NSSI cessation by adulthood indicates improvement over continued engagement, although earlier experiences continue to influence adult psychological health. Improved emotion regulation, reduced self-criticism, and greater flourishing appear to be barriers to continuation and key targets for prevention and intervention among individuals with lived experience.