Low implicit and explicit aversion toward self-cutting stimuli longitudinally predict nonsuicidal self-injury.

Nonsuicidal self-injury (NSSI) is the direct and intentional destruction of one’s own body tissue in the absence of suicidal intent (e.g., cutting or burning one’s skin; Nock, 2010). Millions of people engage in these behaviors each year (Klonsky, 2011), with especially high rates in adolescent, young adult, and clinical populations (e.g., 15% to 60%; see Nock, 2010). Although NSSI itself is a concerning behavior, it is most alarming because of its strong association with suicidal self-injury. In fact, recent evidence indicates that NSSI is a stronger longitudinal predictor of future suicidal self-injury than prior suicidal self-injury (e.g., Wilkinson, Kelvin, Roberts, Dubicka, & Good-year, 2011). Given its prevalence and dangerousness, there is an urgent need to identify individuals at-risk for engaging in NSSI. Unfortunately, the nascent literature on the longitudinal prediction of NSSI has produced few powerful and consistent predictors of NSSI. Perhaps the most effective known predictor of NSSI is prior NSSI, which is moderately correlated with future NSSI and tends to wipe out most other effects when simultaneously entered with other variables (e.g., Chapman, Derbidge, Cooney, Hong, & Linehan, 2009; Tuisku et al., in press). This highlights the need for additional factors that powerfully predict future NSSI. Several studies have tested the hypothesis that depression represents such a factor; however, as a whole, this literature reveals that depression often is weakly and inconsistently associated with future NSSI. Some studies have obtained relatively small but significant effects (e.g., Guerry & Prinstein, 2010; You, Lin, & Leung, 2013); others have found that this effect disappears when controlling for factors such as prior self-injury and instability of rumination (e.g., Selby, Franklin, Carson-Wong, & Rizvi, 2013; Wilcox et al., 2012); and still others have found no effect of depression (e.g., Glenn & Klonsky, 2011; Tuisku et al., in press). Evidence for the predictive ability of factors related to emotion dysregulation is stronger, but these effects also tend to be weak compared with prior self-injury (e.g., Wilcox et al., 2012; You et al., 2013). Taken together, this literature suggests the need for more effective NSSI predictors. Ideally, such predictors would be powerful, easy to assess, unique from traditional factors such as emotion dysregulation, and able to predict above and beyond prior self-injury. The primary goal of the present study was to evaluate a novel factor that recent theory and research suggest may meet these criteria—low aversion to self-cutting stimuli. Given that affective reinforcement (i.e., feeling better after NSSI) is the primary reason that most people give for engaging in NSSI (Klonsky, 2007; Nock & Prinstein, 2005), this factor has received attention as a potential risk factor for NSSI. However, an accumulating literature indicates that it is natural to display increased positive affect and diminished negative affect (compared with baseline) after the removal of a physically painful stimulus (e.g., Franklin, Lee, Hanna, & Prinstein, 2013; Tanimoto, Heisenberg, & Gerber, 2004). This natural pain offset relief helps to explain the affective reinforcement of NSSI. Surprisingly, this pain offset relief does not distinguish between non-NSSI and NSSI groups (e.g., Franklin et al., 2010, Franklin, Puzia, et al., 2013). In contrast, what we conceptualize as the barriers to NSSI powerfully discriminate between these groups. For example, many people avoid NSSI because of the pain involved in these behaviors, and laboratory studies have shown that individuals who engage in NSSI often are willing to endure pain because they believe that they deserve punishment (e.g., Franklin, Aaron, Arthur, Shorkey, & Prinstein, 2012; Hooley, Ho, Slater, & Lockshin, 2010; Hooley & St. Germain, in press). The aversion to NSSI stimuli also represents an important barrier to self-injurious behaviors. The aversion to injury and stimuli associated with injury is potent and instinctive (cf. Ohman & Mineka, 2001). Indeed, in normative samples, mutilation stimuli tend to produce the most negative affective reactions across a range of self-report and psychophysiological measures (e.g., Bradley, Codispoti, Cuthbert, & Lang, 2001). Recent theoretical (e.g., Franklin, Puzia, et al., 2013; Joiner, Ribeiro, & Silva, 2012) and cross-sectional empirical work (Glenn & Klonsky, 2010; Plener, Bubalo, Fladung, Ludolph, & Lule, 2012), however, suggests that individuals who engage in NSSI overcome this instinctive aversion to self-injury stimuli. Recently, we found that diminished implicit and explicit aversion to self-cutting stimuli powerfully distinguished between NSSI and non-NSSI groups at baseline (ds = .61 to 1.23) and were strongly associated with lifetime NSSI frequency (rs = .42 to .46; Franklin, Lee, Puzia, & Prinstein, in press). This suggests that diminished aversion to self-cutting stimuli may longitudinally predict NSSI. Nevertheless, it should be noted that baseline group separation does not necessarily lead to longitudinal prediction. For example, an NSSI-specific version of the Implicit Association Test (IAT) distinguishes between non-NSSI and NSSI groups as baseline (d = 1.20; Nock & Banaji, 2007), but does not appear to prospectively predict NSSI (Glenn & Klonsky, 2011). In the present follow-up to Franklin et al. (in press), we evaluated the hypothesis that greater reductions in aversion to self-cutting stimuli would be associated with more frequent engagement in future NSSI. To test this hypothesis, we measured implicit and explicit affective aversion to self-cutting stimuli in a sample of individuals with a history of self-cutting and then measured their NSSI frequency over the ensuing 6 months. We measured explicit aversion with a computerized survey that asked participants to rate the pleasantness/unpleasantness of self-cutting images. Because individuals may be unwilling or unable to accurately report their affective responses to self-injury stimuli (cf. Nisbett & Wilson, 1977; Nock et al., 2010), we additionally measured implicit aversion to these same self-cutting stimuli with the Affect Misattribution Procedure (AMP; Payne, Cheng, Govorun, & Stewart, 2005). To investigate the independence of these factors, we tested their abilities to predict NSSI uniquely from other theoretically important factors including prior self-injury, number of NSSI methods, self-prediction of future NSSI, implicit identification with self-cutting, emotion reactivity, and therapy status. Finally, in addition to self-cutting, we separately examined overall noncutting severe NSSI behaviors (i.e., burning, scraping, severe hitting, etc.) as an outcome variable. This allowed us to investigate whether diminished aversion to self-cutting was specific to self-cutting or applied to NSSI more broadly.