Genetic liability for autism: the behavioural expression in relatives

Abstract

Twin and family studies have suggested that, in addition to causing the full syndrome of autism, the genetic liability for autism may also cause milder, but qualitatively similar behavioural characteristics in non-autistic relatives. Together these characteristics have been referred to as constituting a broad autism phenotype and include such phenomena as rigid and aloof personality and language abnormalities. Clarification of the type and range of characteristics that make up the broad autism phenotype are important for studies aimed at elucidating the biological basis of autism. In particular further defining the full phenotypic expression of the genes that cause autism may aid in teasing apart gene-behaviour relationships as well as brain-behaviour relationships. In this paper the pattern of behaviours which define the broad autism phenotype is reviewed, as well as the potential importance of further characterizing this phenotype for future studies of the biological basis of this disorder.