To examine the theory of the mind (TOM) in BPD patients.

Fifteen BPD patients (age>18) meeting criteria for BPD were compared to 16 healthy matched controls on two measures of TOM: mental state decoding (MSD) and mental state reasoning (MSR). MSD is the ability to perceive social cues (faces expression, voices) while MSR is the ability to infer on mental states with experiment, learning, context. MSR was measured by the faux pas recognition task assessing the ability to identify a faux pas in a social situation (range 0-60) and a comic strips task measuring the ability to infer intention (range 0-28). MSD was assessed by a video task reporting the ability to infer false belief and intention of deceit on visual motor action. Depressive symptoms (Beck Depression Inventory) and axis II comorbidity traits (Personality Disorder Questionnaire-4+) were also assessed.

Mean (SD) age was 26.0 (4.1) and two participants were of male gender (6.5%). BPD patients scored significantly lower than controls on the both MSR measures: faux pas task mean (SD) scores of 46.6(14.1) vs 58.0(2.8) (p=0.002) and comic strips mean (SD) scores of 26.1(1.5) vs 27.4(1.3) (p=0.001). No significant differences were found on the video task. Multivariate analyses showed that faux pas score was predicted by BPD diagnosis independently from level of depressive symptoms, history of hypomanic episode, schizotypic and antisocial personality disorder traits (F=4.32, df=6, p< 0.01).

BPD is associated with a TOM deficit on mental state reasoning tasks even after controlling for confounding variables.