A. Lecouteur et al., A BROADER PHENOTYPE OF AUTISM - THE CLINICAL SPECTRUM IN TWINS, Journal of child psychology and psychiatry and allied disciplines, 37(7), 1996, pp. 785-801
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 b
oth twins had autism. In the non-autistic cotwin (i.e. in twin pairs d
iscordant for autism) it was common to find language impairments in ch
ildhood and social deficits persisting into adulthood. Concordance for
this broader phenotype was much greater in MZ pairs than DZ pairs, in
dicating a strong genetic component. Behavioural and cognitive manifes
tations of autism were compared both within and between MZ twin pairs.
The variation was as great within MZ twin pairs as between pairs, sug
gesting that it does not index genetic heterogeneity (although aetiolo
gical heterogeneity probably exists). Current diagnostic practices nee
d reevaluation. Copyright (C) 1996 Association for Child Psychology an
d Psychiatry.