There is substantial evidence that patients with schizophrenia present with impaired Theory of Mind (ToM). ToM impairment has been also reported in euthymic bipolar disorder (BD). However, data from direct comparisons of patients with schizophrenia and BD on ToM abilities are limited.

It has been suggested that different aspects of mentalizing processing, such as epistemic and emotional mental representations, i.e. cognitive and affective ToM, must be separately examined.

The aim of the study was to compare ToM ability and both its cognitive and affective components between schizophrenic and euthymic BD patients.

Fifty three BD type I euthymic patients, 54 patients with schizophrenia and 53 healthy controls (HC) completed a multi-facet battery of ToM tasks, including False belief task, Hinting task and Faux Pas Recognition Test (FP). Besides the overall ability to recognize Faux Pas, two specific components of ToM – cognitive and affective – were assessed with FP. The three groups were matched for gender, age and education.

BD and schizophrenia patients showed no impairment in the False belief task. Schizophrenia patients performed significantly lower than HC and BD patients in Hinting task, FP recognition and affective ToM. Both patient groups were impaired in cognitive ToM. However, only BD patients with a history of psychosis performed significantly lower than HC in affective ToM.

In contrast to schizophrenia patients, euthymic BD patients show a specific deficit only in cognitive but not in affective ToM. Further research on the impact of these deficits on social and occupational functioning is warranted.