Selective interoception impairments and treatment effects in borderline personality disorder.

Patients with borderline personality disorder (BPD) suffer from severe emotional dysregulation and disturbances in body image and self-perception. Interoception, the processing and perception of internal body signals, is closely linked to emotional processing, but it remains unclear whether BPD impairs specific interoceptive facets and how these deficits respond to treatment. We investigated two key interoceptive facets, accuracy and attention, in BPD patients and healthy controls (HC) using self-report and objective measures before (nBPD=55,nHC = 31) and after (nBPD=37,nHC = 31) four-week residential Dialectical Behavior Therapy (DBT)/a waiting interval. Interoceptive accuracy and its metacognitive awareness were evaluated using a heartbeat discrimination task, while interoceptive attention was measured through questionnaires, intensity ratings, and uni- and multivariate neural responses during a functional magnetic resonance imaging (fMRI) interoceptive attention task. Before DBT, BPD patients showed reduced self-reported interoceptive attention, which was associated with more interpersonal problems. Patients further exhibited higher similarity in activity patterns evoked by cardiac interoceptive and exteroceptive attention in the insular and dorsal anterior cingulate cortex. There were no significant group differences in behavioral or self-reported interoceptive accuracy or metacognitive awareness. However, behavioral interoceptive accuracy was impaired in BPD patients with more severe symptoms. After four-week residential DBT, self-reported interoceptive attention significantly improved, while other interoceptive facets showed no significant changes. Our findings indicate that BPD involves selective interoceptive attention disturbances, with only self-reported measures responding to treatment. These results support multifaceted assessments of interoception and the potential benefit of interoceptive attention training for all BPD patients, with additional accuracy training in more severe cases.