Negative Emotional Inhibition in Nonsuicidal Self-Injury

Abstract

The relationship between nonsuicidal self-injury (NSSI) and impulsivity is unclear. There is substantial evidence that people who engage in NSSI report impulsive personality traits, or the tendency to behave impulsively in their daily lives. Indeed, research suggests that self-reported impulsive personality is a risk factor that predicts future occurrences of NSSI. Consistent with the idea that NSSI is used to regulate aversive affect, meta-analysis indicates that it is most strongly related to the trait negative urgency: the predisposition to behave impulsively in the context of negative emotions. In contrast, most laboratory-based studies do not find an association between NSSI and heightened impulsivity in cognitive or behavioral tasks. The studies in this dissertation sought to reconcile this discrepancy in the literature by clarifying how negative emotion might promote impulsive action among individuals who engage in NSSI. To accomplish this aim, we systematically examined inhibitory control over negative emotion using tasks that assess impulsive action during the three stages of cognitive/behavioral inhibition: 1) interference control, 2) action restraint (early response inhibition), and 3) action cancellation (late response inhibition). Study 1 investigated interference control in 33 community adults with a history of NSSI and 31 healthy participants before and after a negative mood induction. As in prior research, the groups demonstrated equivalent interference control at baseline mood, and contrary to expectations, negative mood did not worsen interference control in the NSSI group. These results indicate that NSSI is not associated with impaired negative emotional interference control. Study 2 compared the same participants’ performance on a novel emotional action cancellation task. Although participant groups showed comparable overall task performance, NSSI was associated with poor late response inhibition to negative emotional stimuli (but not to positive or neutral stimuli). To elucidate the specificity of this deficit, Study 3 examined negative emotional response inhibition (NERI) in both early and late stages (action restraint and action cancellation, respectively) among 45 participants with a history of NSSI and 43 healthy controls. Results of this study replicated the association between NSSI and specifically impaired late NERI, which partially mediated the relationship between negative urgency and NSSI history. In sum, the studies in this dissertation indicate that impulsive action in NSSI may be restricted to poor control over negative emotional impulses in the final stage of inhibition, and that this deficit contributes to negative urgency in this population. Impaired late NERI represents an objectively measurable cognitive process that is theoretically linked to self-reported affect dysregulation and impulsive personality traits that increase risk for NSSI. These findings suggest that late NERI may be a mechanism underlying negative urgency in NSSI, encouraging future research to determine its role in risk and maintenance. This dissertation provides a nuanced examination of the relationship between the multifaceted construct of “impulsivity” and NSSI, thus helping to clarify mixed findings in this literature.