title: A multivariate twin study of autistic traits in 12-year-olds: testing the fractionable autism triad hypothesis.
abstract: Autistic traits-social impairment, communication impairment, and restricted and repetitive behaviors and interests-are heritable in the general population. Previous analyses have consistently reported limited genetic and environmental overlap between autistic trait domains in samples assessed in middle childhood. Here we extend this research to parent-report data for 12-year-olds. Data from 5,944 pairs in the Twins Early Development Study were analyzed to explore the domain-specific heritability and degree of shared genetic and environmental influences across different autistic traits in the general population and among individuals scoring in the top 5% of each domain. Sex differences in the etiological estimates were also tested in these analyses. Autistic traits were moderately to highly heritable (0.58-0.88) at age 12. Bivariate genetic correlations in the full sample (0.18-0.40) and the extremes (0.24-0.67), as well as even lower unique environmental correlations, all suggested considerable fractionation of genetic and environmental influences across autistic trait domains, in line with previous findings.
authors.affiliation: Department of Epidemiology, Harvard School of Public Health, 185 Cambridge St., Boston, MA 02114, USA. erobinso@hsph.harvard.edu
authors.forename: Elise B
authors.initials: EB
authors.lastname: Robinson
authors.forename: Karestan C
authors.initials: KC
authors.lastname: Koenen
authors.forename: Marie C
authors.initials: MC
authors.lastname: McCormick
authors.forename: Kerim
authors.initials: K
authors.lastname: Munir
authors.forename: Victoria
authors.initials: V
authors.lastname: Hallett
authors.forename: Francesca
authors.initials: F
authors.lastname: Happé
authors.forename: Robert
authors.initials: R
authors.lastname: Plomin
authors.forename: Angelica
authors.initials: A
authors.lastname: Ronald
mesh_terms: D002648:Child; D002659:Child Development Disorders, Pervasive / Q000235:genetics*; D004200:Diseases in Twins / Q000235:genetics*; D004777:Environment; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D010641:Phenotype; D012727:Sex Characteristics