Cognitive peculiarities in relatives of schizophrenic and schizoaffective patients: heritability and resting EEG-correlates

The role of genetic factors in liability to schizophrenia is well established. It is supposed that different susceptibility genes produce distinct neurobiological and behavioural phenotypes that may each increase the risk for developing schizophrenia. The aim of the study was to search for genetically and pathophysiologically independent domains of mild cognitive disturbances that might be the components of liability to schizophrenia. One hundred and twenty-seven adult relatives of schizophrenic and schizoaffective patients were tested with a battery of cognitive tasks. Results were subjected to a principal component analysis, and factors obtained were further investigated with behavioural genetic methods in 56 families of schizophrenics. Resting EEGs were recorded from a subsample of 66 relatives. Correlations of the cognitive factors with absolute power values of seven frequency bands at 16 derivations were assessed using regression analysis. The study revealed four components of cognitive deficits in relatives of schizophrenics in domains of verbal short-term memory, thinking, communication and attention/working memory, all with substantive heritability except the last. The four components had a partial overlapping, but still distinct patterns of resting EEG correlates. The findings are in line with the assumption that cognitive deficit in high-risk individuals may be decomposed to relatively independent dimensions, each with its specific genetic and pathophysiological background. (C) 2003 Elsevier Science B.V. All rights reserved.