The relationship between non-suicidal self-injury and suicidality

The overall purpose of this study was to explain the overlap and distinctiveness of non-suicidal self-injury (NSSI) and suicidality from a diathesis-stress perspective. The first part of this study evaluated the third variable theory as an explanation for the high rates of lifetime co-occurrence between NSSI and suicidality. Specifically, it was hypothesized that these forms of self-harm share a common vulnerability profile comprised of five affective, cognitive and behavioural diatheses. The second part of this study tested the hypothesis that NSSI and suicidality become distinguishable on the basis of immediate, proximal stressors, namely psychache and survival and coping beliefs (SCB). Participants (N = 262) were community individuals aged 16-24 years who reported either no history of self-harm (i.e., no history of NSSI, suicidality, or both), a history of NSSI, suicidality or both, or current NSSI-only or current NSSI+suicidality. They were recruited online to complete an online battery of questionnaires. Using a set of discriminant function analyses, it was found that the vulnerability profile was unable to distinguish between the three self-harm groups, but was able to differentiate the no self-harm group from a collated self-harm group. Result patterns were also analyzed for gender differences. It was also found that a current NSSI+suicidality group exhibited significantly higher psychache and lower SCB (for women only) than a current NSSI-only group. These results suggest that NSSI and suicidality may tend to co-occur because they have similar long-term diatheses, but that they may become more distinct with respect to immediate psychological stressors.