Indicators of genetic liability to schizophrenia: a sibling study of neuropsychological performance

Despite clear evidence of important genetic influences on schizophrenia, identifying the genes involved has been difficult because of the genetic complexity of the phenotype. The use of additional phenotypic measures that are more sensitive to the genetic liability than is the clinical diagnosis should enhance the power to detect small individual genetic effects. The present study assessed the neuropsychological performance of 30 male schizophrenia probands, 30 of their unaffected male siblings, and 20 well controls matched on age, sex, and education in order to identify measures that may be particularly sensitive to the genetic liability to schizophrenia and thus may be useful in gene mapping studies. Siblings showed impaired neuropsychological performance compared to controls on four out of the five measures used. Additional results suggested that Trails B was especially effective at discriminating index siblings from controls, thus supporting its potential utility as a candidate quantitative phenotype to aid in gene mapping studies of the disorder.