Theory of mind performance using a story comprehension task in bipolar mania compared to schizophrenia and healthy controls

Introduction. Theory of mind (ToM) refers to the ability to understand the mental state of self and others. There is limited research into this topic in bipolar disorder (BD), with no previous study examining ToM in a BD group within a psychotic manic phase. Methods. Twenty-eight psychotic manic BD patients were compared with 30 schizophrenia (SCZ) patients and 29 healthy controls (HC). Participants performed a ToM story comprehension task that compared ToM stories and non-ToM stories (which we relabelled non-ToM "semantic" stories). Performance was examined by answering comprehension questions. Results. Both patient groups were equally impaired on their scores for ToM stories (scores BD=10/24, SCZ=9/24, HC=14/24, p<.001). Interestingly, both patient groups showed reduced performance on non-ToM semantic stories (scores BD=12/24, SCZ=9/24, HC=15/24, p<.001); SCZ showed a larger deficit. Reduced ToM performance was correlated with delusion severity in the BD group only. Conclusions. ToM performance was impaired in BD patients experiencing psychotic symptoms. Patient performance was also impaired on the control condition (i.e., non-ToM semantic stories) supporting an additional deficit in semantic processing.