Neuropsychological risk indicators for schizophrenia: a preliminary study of female relatives of schizophrenic and bipolar probands

Evidence of subtle neuropsychological deficits in relatives of schizophrenic probands (REL-SZs) suggests that these are risk indicators for schizophrenia, but little is known about whether neuropsychological performance in REL-SZs differs from that in other groups of relatives. We compared neuropsychological function in female REL-SZs (n = 39), relatives of primarily psychotic bipolar disorder probands (REL-BPs; n = 15), and a normal control group (n = 44). After adjustment for expected intellectual ability (based on reading recognition), REL-SZs showed deficits in verbal and visual memory (Wechsler Memory Scale-Revised logical memories, visual reproductions), and auditory attention (dichotic digits) compared with either REL-BPs or control subjects. Memory, but not dichotic listening differences remained significant after adjusting for current IQ; however, average effect sizes after controlling for either reading or IQ were roughly comparable for these three parameters (d = 0.80, 0.71, and 0.69, respectively). REL-BPs and control subjects showed little difference. Although both schizophrenic and bipolar patients often manifest neuropsychological dysfunction, these preliminary findings indicate subtle neuropsychological deficits only in REL-SZs. Such differences suggest different underlying processes; neuropsychological impairment may, in part, reflect an expression of genetic liability to schizophrenia but not bipolar disorder. Replication with a larger REL-BP sample and with male relatives is needed to evaluate the generalizability of the results.