Variability in the Functions of Non-Suicidal Self-Injury: Evidence from Three Real-Time Monitoring Studies

Abstract Despite functional models of nonsuicidal self-injury (NSSI) helping to explain why people engage in this perplexing behavior, we still lack an understanding of some of the key properties of NSSI functions. Here, we address three unanswered questions about NSSI functions: how much do distinct NSSI functions (1) vary between people over time, (2) vary within people over time, and (3) simultaneously co-occur over time? Data were drawn from three ecological momentary assessment (EMA) studies of self-injurious adult psychiatric outpatients (n = 7), community-based adolescents (n = 15), and community-based adults (n = 9). Across the three studies, there was a total of 271 NSSI episodes (all with corresponding functions captured by EMA). The vast majority (27 of 31; 87%) of participants exhibited unique patterns of NSSI functions during the monitoring periods, indicating high variability between people. The vast majority (26 of 31; 84%) of participants also showed changes in NSSI functions over time, indicating high variability within people. Although it was most common for only one function to be reported for a given NSSI episode, participants endorsed more than one function for 22% to 43% of NSSI episodes, indicating that different functions did simultaneously co-occur. These results underscore that reinforcement processes for NSSI differ from person-to-person, and are both time-varying and multifaceted, which has implications for personalized assessment and treatment of this clinical phenomenon.