How many times and how many ways: The impact of number of nonsuicidal self-injury methods on the relationship between nonsuicidal self-injury frequency and suicidal behavior

Several variables have been proposed as heavily influencing or explaining the association between nonsuicidal self-injury (NSSI) and suicidal behavior. We propose that increased comfort with bodily harm may serve as an incrementally valuable variable to consider. We sought to indirectly test this possibility by examining the moderating role of number of NSSI methods utilized on the relationship between NSSI frequency and lifetime number of suicide attempts, positing that increased variability in methods would be indicative with a greater general comfort with inflicting harm upon one's own body. In both a large sample of emerging adults (n = 1,317) and a subsample with at least one prior suicide attempt (n = 143), results were consistent with our hypothesis. In both samples, the interaction term was significant, with the relationship between NSSI frequency and suicidal behavior increasing in magnitude from low to mean to high levels of NSSI methods. Although frequency of NSSI is robustly associated with suicidal behavior, the magnitude of that relationship increases as an individual engages in a wider variety of NSSI methods. We propose that this may be due to an increased comfort with the general concept of damaging one's own body resulting from a broader selection of methods for self-harm.