Altered pain perception in self-injurious behavior and the association of psychological elements with pain perception measures: a systematic review.

BACKGROUND The pathophysiology of non-suicidal self-injury (NSSI) is controversial. There is growing evidence of altered pain perception in people engaging in NSSI. Some hypotheses have been made on addictive aspects of this behavior. Pain and addictive behavior are modulated by the opioid system, which makes the endogenous opioids one of the candidate neurotransmitters related to NSSI. This article explains the theoretical background on NSSI as an addictive behavior, endogenous opioids involvement and pain perception changes in NSSI and updates the latest findings in this field. The main aim of this paper is a comprehensive review of published studies on pain perception in NSSI and an evaluation of the impact of NSSI functions and other psychological elements on pain perception measures. SUBJECTS AND METHODS We have reviewed six studies of pain perception in participants with NSSI compared with controls. The participants of these studies were not mentally disabled or autistic and did not have a diagnosed personality disorder. RESULTS The reviewed studies have demonstrated a higher pain threshold and longer pain tolerance or endurance in five of six studies. Emotional dysregulation was significantly associated with all pain perception variables in one study. Neuroticism, self-criticism and painful and provocative experiences revealed correlated with pain endurance or pain tolerance. No correlation between pain perception measures and dissociation, hopelessness or locus of control was found. CONCLUSIONS Pain perception was altered in participants with NSSI. Pain perception was associated to emotional dysregulation, self-criticism, neuroticism and painful and provocative experiences. Because of the small number of studies reviewed, results should be seen as guidelines for further studies. They should be replicated on a bigger sample of studies. Further research should focus on pain perception measures in participants with NSSI and an excluded personality disorder.