Neuropsychologic functioning among the nonpsychotic relatives of schizophrenic patients: the effect of genetic loading

Background: We previously reported that the nonpsychotic relatives of schizophrenic patients exhibited disturbances in executive functioning, verbal and visual memory, auditory attention, mental control, and verbal ability. In a 4-year follow-up, we showed that the discriminating power of most of these tests was stable over time. Methods: In this report we compare 41 nonpsychotic persons who have only one schizophrenic first-degree relative (simplex families) with 36 nonpsychotic persons who have two schizophrenic first-degree relatives (multiplex families). Our goal was to test a hypothesis that neuropsychologic deficits would be worse among the latter. Results: Relatives from multiplex families differed significantly from controls on estimated intelligence, immediate and delayed logical memories, and immediate visual reproductions. In contrast, in comparisons with controls, relatives from simplex families only differed on immediate logical memories. Comparisons between relatives from multiplex and simplex families showed that the former group had significantly worse scores for estimated intelligence, immediate and delayed logical memories, and immediate visual reproductions. We also found group × gender interactions: the worse performance of the multiplex group was seen for females. Conclusions: These results are consistent with the idea that neuropsychologic deficits in relatives of schizophrenic patients reflect their degree of genetic predisposition to schizophrenia. They also suggest hypotheses about gender differences in the familial transmission of the disorder.