Induced illusory body ownership in Borderline Personality Disorder

Background One aspect of selfhood that may have relevance for Borderline Personality Disorder (BPD) is variation in sense of body ownership. We employed the rubber hand illusion (RHI) to manipulate sense of body ownership in BPD. We extended previous research on illusory body ownership in BPD by testing: 1) two illusion conditions: asynchronous & synchronous stimulation, 2) relationship between Illusion experience and BPD symptoms, and 3) relationship between illusion experience and maladaptive personality traits. Methods We measured illusion strength (questionnaire responses), proprioceptive drift (perceived shift in physical hand position), BPD symptoms (DIB-R score), and maladaptive personality traits (PID-5) in 24 BPD and 21 control participants. Results For subjective illusion strength, we found a main effect of group (BPD > HC, F = 11.94 p = 0.001), and condition (synchronous > asynchronous, F(1,43) = 22.80, p < 0.001). There was a group x condition interaction for proprioceptive drift (F(1,43) = 6.48, p = 0.015) such that people with BPD maintained illusion susceptibility in the asynchronous condition. Borderline symptom severity correlated with illusion strength within the BPD group, and this effect was specific to affective symptoms (r = 0.48, p < 0.01). Across all participants, trait psychoticism correlated with illusion strength (r = 0.44, p < 0.01). Conclusion People with BPD are more susceptible to illusory body ownership than controls. This is consistent with the clinical literature describing aberrant physical and emotional experience of self in BPD. A predictive-coding framework holds promise to develop testable mechanistic hypotheses for disrupted bodily self in BPD. Highlights The rubber hand illusion (RHI) allows measurement of self-disturbance. People with BPD had greater illusion susceptibility and this correlated with affective symptoms. Interoception stabilizes representations of body ownership, and is impaired in BPD. Illusion strength correlates with psychotic traits across levels of psychopathology. Predictive coding frameworks can probe mechanisms of impaired body ownership in psychopathology.