Objective: Most studies of the DSM-5 proposed non-suicidal self-injury disorder (NSSID) have focused on documenting its prevalence, associated features, and evaluating the validity of the criteria. There is scant data assessing the temporal course, or onset and offset, of NSSID. This study examined the course of NSSID and each criterion over a one-year period. Method: Data were obtained from 171 young adults (mean age = 18.79; 84% women, 92% White, 37% in treatment) with past year NSSI engagement (mean frequency = 12.47, SD = 20.9) who completed a minimum of two, out of three, waves of data collection. Participants completed the Non-Suicidal Self-Injury Disorder Scale along with demographic measures at baseline, 6-month, and 12-month follow-up. Results: Over a third of participants met NSSID criteria at each time point, with moderate persistence (K = 0.42 to 0.46). Chi-square tests revealed significant onset and offset patterns of NSSID and among select criteria. Binary logistic regression analyses revealed that meeting the criterion A (frequency of NSSI) and criterion E (impairment) thresholds at baseline were the only meaningful predictors of diagnostic status at 6- and 12-month follow-up. Limitations: The use of self-report measures and having a homogenous sample restrict generalizability of the findings. Conclusions: Meeting NSSID criteria appears to persist over time, but only 2 of the 6 criteria may be relevant to diagnostic status across time. Further research on the temporal course, reliability, and clinical validity of the proposed disorder, especially within diverse clinically severe, populations is greatly needed.
