Theory of Mind as an endophenotype for schizophrenia spectrum disorder: Study in first episode of psychosis patients and first-degree relatives.

Background: Deficits in Theory of Mind (ToM) had been suggested as a possible endophenotype for unaffected relatives of first episode of psychosis (FEP) patients. There are a limited number of studies which have evaluated ToM deficits among the siblings and parents of FEP patients.

Aim: This study aimed to explore ToM deficits and its correlates among FEP patients, their siblings, parents, and controls.

Methodology: FEP patients (N=102), their parents (N=135), siblings (N=97), and controls (N=167) were evaluated on ToM performance with the Reading the Mind in the Eyes Test (Eyes Test). Interview for sociodemographic variables of age, sex, years of education, and IQ estimation and neurocognitive tests were administered to all groups.

Results: FEP patients had a significantly lower performance on the Eyes Test compared to their siblings and controls. However, no significant differences were found between siblings and parents or siblings and controls.

Conclusion: Attending our results, we found no evidence for ToM deficits as an endophenotype of SSDs. Furthermore, ToM accuracy may be mediated by interaction with other cognitive domains and play a protective role against psychosis in unaffected siblings.