Theory-of-mind understanding and theory-of-mind use in unaffected first-degree relatives of schizophrenia and bipolar disorder.

We assessed theory of mind (ToM) in unaffected first-degree relatives (FDR) of patients with schizophrenia (SC) and bipolar disorder (BD) compared to healthy controls with a revised computerized referential communication task. Results showed that FDR of SC performed worse than FDR of BD and controls on a task requiring ToM-use, but not on a task requiring ToM-understanding. This indicates that deficient ToM-use, rather than ToM-understanding impairments, may represent a potential candidate endophenotype for schizophrenia.