A FAMILY STUDY OF AUTISM - COGNITIVE PATTERNS AND LEVELS IN PARENTS AND SIBLINGS

First-degree relatives of 99 autism probands and of 36 Down's syndrome controls were assessed with standardised tests of intellectual functi oning, reading, and spelling. Higher mean verbal IQ scores, and discre pancies in favour of verbal scores, were characteristic of autism rela tives. No consistent differences were found on performance scales, rea ding, and spelling tests. Among autism relatives, siblings affected wi th the broad phenotype of autism had significantly lower IQ scores and poorer reading and spelling performances than unaffected siblings. Ho wever, the small size of the cognitive difference and the lack of a di stinctive cognitive profile indicates that standardised cognitive meas ures used in this study are unlikely to improve the operationalised de finition of the broad phenotype of autism. The slightly superior verba l performance of relatives in the autism group might represent some fo rm of heterozygote advantage.