Subtle deficits of cognitive theory of mind in unaffected first-degree relatives of schizophrenia patients

Alterations of theory of mind (ToM) and empathy were implicated in the formation of psychotic experiences, and deficits in psychosocial functioning of schizophrenia patients. Inspired by concepts of neurocognitive endophenotypes, the existence of a distinct, potentially neurobiologically based social-cognitive vulnerability marker for schizophrenia is a matter of ongoing debate. The fact that previous research on social-cognitive deficits in individuals at risk yielded contradictory results may partly be due to an insufficient differentiation between qualitative aspects of ToM. Thirty-four unaffected first-degree relatives of schizophrenia patients (21 parents, 8 siblings, 5 children; f/m: 30/4; mean age: 48.1 ± 12.7 years) and 34 controls subjects (f/m: 25/9; mean age: 45.9 ± 10.9 years) completed the ‘Movie for the Assessment of Social Cognition’—a video-based ToM test—and an empathy questionnaire (Interpersonal Reactivity Index, IRI). Outcome parameters comprised (1) ‘cognitive’ versus ‘emotional’ ToM, (2) error counts representing ‘undermentalizing’ versus ‘overmentalizing’, (3) empathic abilities and (4) non-social neurocognition. MANCOVA showed impairments in cognitive but not emotional ToM in the relatives’ group, when age, gender and neurocognition were controlled for. Relatives showed elevated error counts for ‘undermentalizing’ but not for ‘overmentalizing’. No alterations were detected in self-rated dimensions of empathy. Of all measures of ToM and empathy, only the IRI subscale ‘fantasy’ was associated with measures of psychotic risk, i.e. a history of subclinical delusional ideation. The present study confirmed subtle deficits in cognitive, but not emotional ToM in first-degree relatives of schizophrenia patients, which were not explained by global cognitive deficits. Findings corroborate the assumption of distinct social-cognitive abilities as an intermediate phenotype for schizophrenia.