Neuropsychological dysfunctions in siblings discordant for schizophrenia

Although cognitive impairments are well recognized in patients with schizop hrenia, it is unclear which impairments are due to a genetic predisposition and which are caused by secondary disease effects or phenotype. The aim of this study is to investigate: the possible relationship between genetic vu lnerability to schizophrenia and cognitive functioning. Three groups of sub jects were compared: 14 patients with schizophrenia, 15 healthy siblings an d 32 healthy control subjects. All subjects were tested neuropsychologicall y. The raw test data were rescaled to standard equivalents (z-scores). Subj ects' z scores on tests assessing the same cognitive domain were clustered and analyzed. Differences in cognitive functioning were found in the domain s of abstraction, attention, executive functioning, spatial memory, and sen sory-motor functioning. The schizophrenic probands were impaired on all the se five domains whereas the healthy probands showed impairments on executiv e functioning and partially on sensory-motor functioning. Furthermore, for spatial memory the significant finding could mainly be attributed to impair ed functioning in the patients, but not healthy siblings or control subject s, whereas for executive functioning patients and healthy siblings seemed e qually impaired as compared to control subjects. The planning time of the T ower of London (TOL) and the initiation time of the Motor Planning Task (MP T) were used for measures of executive functioning, while the 'time to move of the Motor Planning Task' was used as measures of sensory motor function ing. These results suggest that the cognitive abnormalities in schizophreni a that may be related to genotype are represented in the domain of executiv e functioning and to some extent in the domain of sensory-motor functioning . (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.