What happens to young adults who have engaged in self-injurious behavior as adolescents? A 10-year follow-up

This study examined the longitudinal associations between non-suicidal self-injury (NSSI) in early adolescence and various positive and negative aspects of mental health in young adulthood. The participants were a cohort of regular school students (n = 1064) in grades 7–8 from a Swedish municipality. Nine hundred and ninety-one of these completed an 11-page questionnaire (T1: M(age) = 13.7; 50.3% girls); 1 year later, 984 students completed the questionnaire again (T2: M(age) = 14.8; 51.1% girls); and 10 years later, 557 took part (T3: M(age) = 25.3; 59.2% women). The prevalence of any NSSI (≥ 1 instance) decreased from about 40% in adolescence to 18.7% in young adulthood, while the prevalence of repetitive NSSI (≥ 5 instances) decreased from about 18 to 10%. Compared to individuals who reported no NSSI as adolescents, and controlling for gender and psychological difficulties in adolescence, adolescents with stable repetitive NSSI (i.e., repetitive NSSI at both T1 and T2) showed significantly higher levels of stress, anxiety, NSSI, and difficulties in emotion regulation 10 years later. Even infrequent and unstable repetitive NSSI in adolescence was associated with negative outcomes in young adulthood. These results suggest that stable repetitive NSSI in adolescence is a strong risk factor for mental health problems in young adulthood and that occasional engagement in NSSI in adolescence is an indicator of vulnerability for poorer mental health in young adulthood. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s00787-020-01533-4) contains supplementary material, which is available to authorized users.