Previous research has found associations between non-suicidal self-injury (NSSI) and suicidal thoughts and behaviors (STBs), yet the nature of this relationship remains equivocal. The goal of the present study was to examine how lifetime NSSI frequency and individual NSSI functions relate to a history of suicidal ideation, plan, and attempt. Data were collected via a large (N=13,396) web-based survey of university students between the ages of 18 and 29. After demographics and psychiatric conditions were controlled for, we found a positive curvilinear relationship between NSSI frequency and each of the suicide outcomes. When examined among those with STBs, bipolar disorder and problematic substance use remained positively associated with risk for suicide attempt, but not NSSI. Analyses of individual NSSI functions showed differential associations with STBs of varying severity. Specifically, nearly every NSSI function was significantly related to suicide attempt, with functions related to avoiding committing suicide, coping with self-hatred, and feeling generation (anti-dissociation) showing the strongest risks for suicide attempt. From both clinical and research perspectives, these findings suggest the importance of assessing multiple reasons for engaging in self-injury.
Suicidal thoughts and behaviors (STBs) (Kessler et al., 1999) and non-suicidal self-injury (NSSI) are serious public health problems in young adults (Swannell et al., 2014). In the National Comorbidity Survey, young age is consistently related to elevated risk for a range of suicidal thoughts and behaviors (Kessler et al., 1999 and Borges et al., 2008). Though lifetime prevalence estimates for NSSI vary considerably (1.5–54.8%), results from a recent meta-analysis suggest that after accounting for methodological differences across studies, about 13.4% of young adults report ever having engaged in NSSI (Swannell et al., 2014).
Although related and frequently co-occurring (Nock et al., 2006, Muehlenkamp and Gutierrez, 2007 and Whitlock and Knox, 2007), NSSI and suicidal thoughts and behaviors differ on a number of domains including frequency, lethality, and intention (Hamza et al., 2012). The two phenomena are generally distinguished based on the presence of intent to die (Andover et al., 2012). The nature of the relationship is complex and not yet fully elucidated, several studies have found that a prior history of NSSI has been identified as one of the strongest predictors of suicidal thoughts and behaviors (Lewinsohn et al., 1994, Wilkinson et al., 2011 and Whitlock et al., 2013). Shedding light on the ways in which various aspects of NSSI relate to STBs is the first step in understanding the potential mechanisms through which these phenomena are linked. It might also contribute to our understanding of the transition from suicidal thoughts to suicide attempts, a crucial line of inquiry in studies of suicide (Klonsky and May, 2013). Further, the majority of the existing literature on NSSI frequency and suicide attempt has been carried out in clinical samples, which limits generalizability of these findings to a broader population of young adults.
