title: A broader phenotype of autism: the clinical spectrum in twins.
abstract: The diagnostic boundaries of the behavioural phenotype for autism were examined in 28 MZ pairs and 20 DZ same-sex twin pairs, where one or both twins had autism. In the non-autistic cotwin (i.e. in twin pairs discordant for autism) it was common to find language impairments in childhood and social deficits persisting into adulthood. Concordance for this broader phenotype was much greater in MZ pairs than DZ pairs, indicating a strong genetic component. Behavioural and cognitive manifestations of autism were compared both within and between MZ twin pairs. The variation was as great within MZ twin pairs as between pairs, suggesting that it does not index genetic heterogeneity (although aetiological heterogeneity probably exists). Current diagnostic practices need re-evaluation.
authors.affiliation: Fleming Nuffield Unit, Newcastle Upon Tyne, U.K.
authors.forename: A
authors.initials: A
authors.lastname: Le Couteur
authors.forename: A
authors.initials: A
authors.lastname: Bailey
authors.forename: S
authors.initials: S
authors.lastname: Goode
authors.forename: A
authors.initials: A
authors.lastname: Pickles
authors.forename: S
authors.initials: S
authors.lastname: Robertson
authors.forename: I
authors.initials: I
authors.lastname: Gottesman
authors.forename: M
authors.initials: M
authors.lastname: Rutter
mesh_terms: D000203:Activities of Daily Living; D000704:Analysis of Variance; D001321:Autistic Disorder / Q000150:complications / Q000175:diagnosis / Q000235:genetics*; D003147:Communication Disorders / Q000235:genetics; D004200:Diseases in Twins; D005260:Female; D005500:Follow-Up Studies; D018740:Genetic Heterogeneity; D006801:Humans; D007360:Intelligence; D007406:Interview, Psychological; D008297:Male; D010641:Phenotype; D012917:Social Adjustment; D012920:Social Behavior Disorders / Q000235:genetics; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D006113:United Kingdom