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MMN amplitude in first-degree relatives of psychotic disorders: Links with cognition and schizotypy

Background: Mismatch negativity (MMN) amplitude is reliably reduced in psychotic disorders. While several studies have examined this effect in first-degree relatives of individuals with schizophrenia, few have sought to quantify deficits in relatives of individuals with other psychotic disorders. While some studies conclude that, compared to healthy subjects, first-degree relatives of schizophrenia show reduced MMN, others contradict this finding, a discrepancy which extends to two recent meta-analyses. Furthermore, though MMN is often shown to be associated with cognitive impairments and clinical symptoms in psychotic disorders, to our knowledge no studies have sought to examine these relationships in studies of first-degree relatives. Method: The present study sought to clarify the extent of MMN amplitude reductions in a large sample of siblings of individuals with diverse psychotic disorders (n=65), compared to cases with psychosis (n=220) and never psychotic comparison subjects (n=252). We further examined associations of MMN amplitude with cognition and schizotypal symptoms across these groups. Results: We found that MMN amplitude was intact in siblings compared to cases with psychosis. MMN amplitude was associated with cognition and schizotypal symptoms dimensionally across levels of familial risk. Conclusions: The present results imply that MMN amplitude reductions emerge as a result of, or in conjunction with, clinical features associated with psychosis. Such findings carry important implications for the utility of MMN amplitude as an indicator of inherited risk, and suggest that this component may be best conceptualized as a marker for clinical symptoms and cognitive impairments, rather than risk for psychosis per se.