Persistent antinociception through repeated self-injury in patients with borderline personality disorder

Patients with borderline personality disorder, mostly female, exhibit severe autoaggressive behavior, namely an intentionally performed, nonsuicidal self-injury and severe blunting of pain perception, the mechanism of which is hitherto not understood. Because the nociceptive system displays a high degree of plasticity, the aim of this study was to analyze the relationship of pain perception to self-injurious behavior. Pain perception of mechanical and chemical noxious stimuli was studied by quantitative sensory testing in 22 patients (15 female, 7 male) with borderline personality disorder (BPD) according to DSM-IV and 22 age- and gender-matched controls. BPD patients exhibited a significantly higher pain threshold to pinprick stimuli (2.7 times higher than healthy control subjects), and significantly lower pain ratings to mechanical (pinprick, -28%) and chemical (capsaicin, -38%) stimulation. Capsaicin-induced pain decayed significantly faster in BPD patients (τ=49 seconds) than in controls (τ=76 seconds). These alterations of pain perception were generally present in the female, but not in the male subgroup of BPD patients. Analysis of pain intensity vs unpleasantness suggested that primarily the unpleasantness aspect of the pain experience was reduced. Blunting of pain sensation was significantly predicted by the recency of self-injurious behavior (multiple r=0.58). In line with recent data, we suggest an excess of endogenous antinociception in BPD patients resulting from self-inflicted multiple injuries. This exaggerated pain control is conceived to operate via an uncoupling of the evaluative or emotional-affective from the sensory-discriminative dimension of pain.