IQ and the genetics of autism.

While there seems to be general agreement that genetic factors play some role in the etiology of autism, many important questions remain unresolved. The purpose of this paper is to review five issues with respect to the association between low IQ and autism from a familial-genetic viewpoint: (1) does IQ estimate the severity of the autistic genotype?; (2) what is the relationship between probands' and sibs' IQs?; (3) what is the relationship between parents' and probands' IQs?; (4) why do females with autism have lower IQs than males with the disorder?; and (5) does IQ vary with the cause of autism? With respect to each issue, possible resolutions are outlined, as are the implications for understanding the genetic mode of transmission. The review concludes with a possible model for the genetic etiology of autism.