Supplementary Material for: A neural signature of touch aversion and interpersonal problems in Borderline Personality Disorder

Introduction: Patients with borderline personality disorder (BPD) suffer from severe social impairments and interpersonal problems. Social touch can provide comfort and facilitate the maintenance of social bonds, and preliminary evidence indicates a negative evaluation of social touch in patients with BPD. However, the neural mechanisms underlying aberrant touch processing in BPD and its role for social impairments are still unclear.

Methods: We recruited 55 BPD patients and 31 healthy controls and used functional magnetic resonance imaging to probe neural responses to slow (i.e. C-tactile (CT)-optimal; affective) and fast (i.e. CT-suboptimal; discriminative) touch before and after four weeks of a residential dialectical behavior therapy (DBT) program. In addition to assessing BPD symptoms and interpersonal problems, we evaluated touch allowance maps and the attitude towards social touch.

Results: BPD patients showed a comprehensive negative bias towards social touch before the DBT, evident in a significantly more negative attitude towards and reduced comfort zones of social touch compared to healthy controls. Activation in the posterior insular cortex in response to CT-optimal touch was significantly reduced and correlated with the severity of interpersonal problems in BPD patients. Despite significant improvements in overall BPD symptom load, dysfunctional social touch processing persisted after four weeks of DBT, indicating trait-like disturbances in BPD.

Conclusions: An impaired insula-mediated integration of affective and sensory components of touch may constitute a clinically relevant biological signature of the complex interpersonal problems in BPD.