What predicts suicidality among people who self-injure? Evidence for acquired capability via pain habituation and NSSI severity.

Individuals who engage in non-suicidal self-injury (NSSI) are at heightened risk for suicide. However, not all individuals who self-injure are equally vulnerable, and it remains unclear which specific NSSI characteristics confer greater risk for suicidal behavior and suicide attempts. This study examined a large online sample (N = 1227) of individuals who had engaged in NSSI within the past six months, assessing associations between suicidal outcomes and NSSI-related variables, including frequency, number of methods used, injury severity, need for medical attention, pain experienced during NSSI, and perceived changes in pain over time. Participants completed self-report measures of suicidal behavior (using the Suicide Behaviors Questionnaire-Revised, SBQ-R), lifetime suicide attempts, and a battery of items characterizing their NSSI behavior. Multiple regression analyses were used to predict SBQ-R scores, and negative binomial regressions were conducted for the count outcome of past suicide attempts, adjusting for gender and age. Results indicated that higher NSSI frequency, use of a greater number of methods, greater self-reported severity and need for medical attention, as well as reductions in pain over time were all significantly associated with greater suicidal behavior and more suicide attempts. These findings align with the interpersonal theory of suicide, which posits that habituation to painful stimuli can contribute to an increased acquired capability for suicide. The results underscore the importance of evaluating specific NSSI characteristics during suicide risk assessments in clinical settings and highlight changes in NSSI associated pain and past need for medical attention as possible targets of future research.