Impaired theory of mind (ToM) is an assumed feature of borderline personality disorder (BPD). Yet, no studies have compared ToM abilities in patients with BPD, other personality disorders, and healthy controls, or investigated the relationship between ToM and severity of psychopathology and interpersonal problems. In this study, ToM was investigated by the Movie for the Assessment of Social Cognition. No differences were found between the three groups in overall ToM abilities. The BPD group was, however, characterized by more excessive ToM (interpreted as hypermentalization). Yet, when differentiating between BPD and further severity indicators, excessive ToM was not specifically associated with a BPD diagnosis per se. Finally, there was a moderate association between hypermentalization and interpersonal problems in the BPD group. This study suggests that BPD patients tend to hypermentalize when they misinterpret social information, and that this tendency is related to the severity of their psychopathology.
Keywords: borderline personality disorder; hypermentalization; interpersonal problems; social cognition; theory of mind.