Longitudinal development of non-suicidal self-injury disorder in adolescence: Prospective prediction of stability and change by identity development, depression, trauma, and resilience

Background: With the introduction of non-suicidal self-injury disorder (NSSI-D) in DSM-5, the field obtained a standardised set of criteria to study those engaging in more severe and chronic NSSI. To date, no previous research has studied the development of NSSI-D longitudinally, leaving questions on its stability and potential prospective predictors unanswered.
Methods: 2162 community adolescents (M = 15.00 years, SD = 1.88, 53.9 % girls at T1) completed a set of self-report questionnaires for three consecutive years and were classified into three severity-based NSSI subgroups (no-NSSI, subthreshold-NSSI, NSSI-D). Multinomial logistic regression analyses were used to prospectively predict subgroup membership by age, gender, identity development, depressive symptoms, traumatic experiences, and resilience.
Results: At baseline, the sample was distributed over the no-NSSI group (88 %), the subthreshold-NSSI (6 %) and NSSI-D (6 %) groups. These groups respectively showed high (93.5 %), low (25 %) and moderate (47.5 %) stability over one-year intervals. Longitudinally, higher levels of identity confusion and trauma significantly increased the likelihood of transitioning to subthreshold-NSSI. Moreover, boys had a higher likelihood of transitioning from NSSI-D to no-NSSI over the course of one year.
Conclusions: This three-year study provides the first indication of the longitudinal course of NSSI-D with the current set of DSM-5 criteria. Clinically, the results suggest the particular potential of identity confusion and trauma as prevention targets in community adolescents.