Relative risk of neurological signs in siblings of patients with schizophrenia

Objective: First-degree relatives of patients with schizophrenia appear to have subtle neurological signs, suggesting that these measures could serve as intermediate phenotypes in genetic studies of schizophrenia. The strengt h of a possible genetic component is unknown, however, leaving it uncertain whether such traits could increase the power to find schizophrenia suscept ibility loci. The authors' goal was to investigate the strength of this pos sible genetic component. Method: They estimated the relative risk of neurological impairments in a l arge group of siblings of patients with schizophrenia. Two standard neurolo gical scales (the Neurological Evaluation Scale and the Woods Scale) were u sed to examine 115 patients, 185 of their siblings, and 88 normal compariso n subjects. Results: There were significant differences between the siblings of patient s with schizophrenia and the normal comparison subjects only on the Woods S cale. Relative risk of neurological impairment was significantly increased in the sibling group, but the significance was weak to moderate. Neurologic al impairment was not redundant with several other intermediate phenotypic measures based on cognitive impairment. Conclusions: These data suggest that neurological signs cluster in patients with schizophrenia and their families and could possibly identify a unique component of genetic variance for risk of schizophrenia. However, the fair ly low relative risk and the uncertain pathophysiology of such signs may li mit their usefulness.