Developmental pathways of repetitive non-suicidal self-injury: predictors in adolescence and psychological outcomes in young adulthood

BACKGROUND: Much longitudinal research has been carried out on non-suicidal self-injury (NSSI) during the last decades, but there still is a lack of studies of the individual developmental pathways of NSSI from adolescence into young adulthood. The aim of the present study was to investigate individual developmental pathways of repetitive non-suicidal self-injury (repNSSI) from adolescence into young adulthood, including adolescent predictors and psychological outcomes in young adulthood. Three developmental pathways were targeted: stable adolescence-limited repNSSI; repNSSI prolonged into young adulthood; and late-onset repNSSI; with no repNSSI as comparison. METHODS: Data were taken from a cohort of compulsory school students (N = 1064) in grades 7–8 in a Swedish municipality. The cohort was followed longitudinally, and this study included all individuals (n = 475) with NSSI data from three waves: T1 (when they were 13–15 years old); T2 (one year later); and T3 (ten years later). RepNSSI was operationalized as self-reports of at least 5 instances of NSSI during the past six/twelve months. RESULTS: The two pathways that involved stable repNSSI were observed significantly more often than expected by chance, with the strongest overrepresentation for the Prolonged RepNSSI pathway. Still, most adolescents who engaged in stable repNSSI stopped this before reaching young adulthood. Those who stopped did not, however, show a significantly better psychological adjustment in young adulthood than those who continued. Compared to participants with no repNSSI, participants who had stopped still reported significantly more stress, anxiety, and emotional dysregulation. As to the prediction of late onset NSSI, the findings were less robust, but sporadic NSSI at T1 and poor sleep at T2 were significant predictors, whereas depressive symptoms fell just short of significance at both timepoints. CONCLUSIONS: The present results indicate that among adolescents who engage in stable adolescent repNSSI (1) significantly more individuals than expected by chance still engage in repNSSI ten years later, and (2) those who stop engaging in repNSSI do not show significantly better psychological adjustment than those who still engage in it. The present findings also indicate that late onset of repNSSI as reported in young adulthood to some extent is predictable from symptom measures ten years earlier.