Etiological heterogeneity and intelligence test scores in patients with schizophrenia.

Previous research has indicated that patients with a family history of schizophrenia show a greater degree of cognitive and neuropsychological impairment than patients without a family history. We examined the neurocognitive performance, using the WAIS-R, of 51 patients with a family history (familial) and 103 patients without a family history (sporadic) to determine if differences exist that may help to explain the heterogeneous neuropsychological profile of the illness. The family history groups did not differ with respect to gender, diagnosis, ethnicity, age, age of onset, education or duration of illness. Multivariate analyses, covarying for age of onset and education, showed the sporadic group performed significantly better than the familial group on the digit symbol and object assembly subtests, with a trend level difference in overall performance IQ score. Additionally, we identified significant gender differences in favor of males for full scale and verbal IQ, the information, digit span, block design, and arithmetic subtests, and at a trend level, the picture assembly subtest. The family history group differences reflect relative dysfunction in visual attention and scanning, visuomotor control, and spatial processing and reasoning. Overall, the results suggest that sporadic patients have better perceptual-organizational skills and faster speed of processing.