Quantifying the Importance of Lifetime Frequency Versus Number of Methods in Conceptualizing Nonsuicidal Self-Injury Severity

Objective: Extant literature has generally conceptualized nonsuicidal self-injury severity in terms of its frequency, although more recently researchers have assessed nonsuicidal self-injury severity by the number of different methods used. There is limited evidence, however, regarding the interaction of these indices in the prediction of clinical severity. Method: The current study aimed to examine these relationships among 2.707 undergraduate students (70% female, M-age = 20.60, 29.95% with nonsuicidal self-injury history) who completed online self-report questionnaires. Analyses utilized structural equation modeling trees and structural equation modeling forests to identify potential subgroups based on nonsuicidal self-injury frequency and/or methods in relation to indicators of clinical severity. Results: Results revealed splits in the following: (a) frequency (between 0 and 1 act); (b) among those with >= 1 acts, frequency (between 8 and 9 acts); (c) among those with >= 1 acts, number of methods (between I and 2 methods); and (d) among those with >= 9 acts and >= 2 methods, frequency (between 15 and 16 acts). Structural equation modeling forest findings demonstrated the relative importance of nonsuicidal self-injury frequency in predicting clinical severity. Conclusions: Results suggest that although nonsuicidal self-injury frequency provides a marker of clinical severity, the combination of frequency and the number of methods used may be more valuable in determining severity.