Psychopathology and Theory of Mind in patients with personality disorders

People with mental disorders frequently suffer from deficits in the ability to infer other's mental states (Theory of Mind; ToM). Individuals with borderline personality disorder (BPD) show ToM deficits characterized by exceeding ToM (over-attributions of mental states). The present study analyzed associations between ToM, BPD severity, and depression severity in patients with BPD and other personality disorders.

We analyzed ToM abilities in 128 patients with BPD and 82 patients with 'mixed and other personality disorders' (MOPD). MOPD are diagnosed if symptoms of multiple personality disorders are present without any set of symptoms being dominant enough to allow a specific diagnosis. We used the movies for the assessment of social cognition (MASC) to measure ToM abilities, the Patient Health Questionnaire (PHQ-9) to assess severity of depression and the McLean Screening Instrument for Borderline Personality Disorder (MSI-BPD) to assess the severity of BPD symptoms.

Both symptoms of BPD and depression were associated with exceeding ToM in separate regressions. Using a stepwise regression, only the association of depression severity with exceeding ToM was reliable. Patients with BPD and MOPD did not differ in exceeding ToM. Age was most reliably associated with ToM.

The results imply that exceeding ToM is associated with general psychopathology instead of BPD-symptoms in specific. Patients with MOPD show deficits similar to BPD patients.