Executive cognitive impairment has been found in families affected by schizophrenia and is a putative endophenotype. We wished to explore its genetic basis further by studying the association between impairment and genetic loading for schizophrenia. We studied 30 schizophrenia patients with a family history of schizophrenia, 53 of their nonpsychotic first-degree relatives (familial), 32 patients with schizophrenia but no known family history of psychosis, 52 of their first-degree relatives (nonfamilial), and 47 normal controls. They were tested using the National Adult Reading Test (NART), Trails A and B, Verbal fluency tasks, and a computerized version of the Wisconsin Card Sorting Test (WCST). Familial, but not nonfamilial, relatives were impaired on NART, letter fluency, Trails B, and WCST total errors. They were inferior to nonfamilial relatives on letter fluency and Trails A. Both sets of relatives were impaired on Trails B controlling for Trails A, and on WCST categories achieved. There were no significant differences between schizophrenia patients with and without a family history. Our results suggest that executive deficits qualitatively similar to those seen in those with schizophrenia reflect familial susceptibility, even taking early IQ and education into consideration, consistent with a genetic mechanism.
Copyright 2007 Wiley-Liss, Inc.