Non-suicidal self-injury (NSSI) describes the deliberate and direct injuring of body tissue without suicidal intent for purposes not socially sanctioned (International Society for the Study of Self-injury;ISSS). Converging evidence suggests that the most common function of NSSI is to regulate negative emotional experiences (e.g., to stop bad feelings). In fact, self-injurers report more frequent and intense negative emotions, a reduction in negative emotions following a self-injurious act, and more emotion dysregulation than non-injurers. Taken together, research suggests that NSSI serves an emotion regulation function for individuals who struggle to regulate emotion. Therefore, careful examination of emotion dysregulation in NSSI could substantially improve knowledge about etiology, prevention, and treatment. Thus far, most of what we know about emotion in NSSI is based on self-report studies, which arguably provide only a crude understanding of emotional deficits. Research guided by an affective science framework could provide more nuanced and clinically useful information about emotion in NSSI. Specifically, emotion can be separated into multiple components, each of which represents a potential source of impairment in disorders characterized by emotion dysregulation. The present study will apply this framework to the study of emotion in NSSI by employing the eyeblink startle reflex, a well-validated physiological measure used to study emotional processing. More specifically, two possible sources of emotion dysregulation will be examined: the magnitude of the startle reflex will be measured 1) during the presentation of emotional and neutral pictures (i.e., to index emotional reactivity) and 2) several seconds following the presentation of these stimuli (i.e., to index return to emotional baseline). The time-course of emotional recovery following aversive stimuli will be further examined in a second study. The study protocol will be administered to a self-injuring and two non-injuring control samples (i.e., affectively distressed non-injurers and non-affectively distressed non-injurers).The long-term goal is to generate more precise knowledge regarding the source and nature of emotional dysregulation in NSSI that can guide the design and implementation of treatments. PUBLIC HEALTH RELEVANCE: Rates of NSSI are disproportionately high in adolescents and young adults. Other than Dialectical Behavior Therapy (DBT), which is an intensive, most often inpatient, treatment program for self-injurers with borderline personality disorder, there is currently no treatment for self-injury. This project represents the first step in a programmatic line of research to generate clinically useful models of emotion dysregulation in NSSI to guide the development of effective interventions.