Strong genetic influences on the stability of autistic traits in childhood.
OBJECTIVE
Disorders on the autism spectrum, as well as autistic traits in the general population, have been found to be both highly stable across age and highly heritable at individual ages. However, little is known about the overlap in genetic and environmental influences on autistic traits across age and the contribution of such influences to trait stability itself. The present study investigated these questions in a general population sample of twins.


METHODS
More than 6,000 twin pairs were rated on an established scale of autistic traits by their parents at 8, 9, and 12 years of age and by their teachers at 9 and 12 years of age. Data were analyzed using structural equation modeling.


RESULTS
The results indicated that, consistently across raters, not only were autistic traits stable, and moderately to highly heritable at individual ages, but there was also a high degree of overlap in genetic influences across age. Furthermore, autistic trait stability could largely be accounted for by genetic factors, with the environment unique to each twin playing a minor role. The environment shared by twins had virtually no effect on the longitudinal stability in autistic traits.


CONCLUSIONS
Autistic traits are highly stable across middle childhood. and this stability is caused primarily by genetic factors.
Department of Psychology at the the University of Essex. Electronic address: kholmboe@essex.ac.uk.
Karla
K
Holmboe
Medical Research Council (MRC) Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, King's College London.
Fruhling V
FV
Rijsdijk
Medical Research Council (MRC) Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, King's College London.
Victoria
V
Hallett
Medical Research Council (MRC) Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, King's College London.
Francesca
F
Happé
Medical Research Council (MRC) Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, King's College London.
Robert
R
Plomin
University of London.
Angelica
A
Ronald
D000367:Age Factors; D002648:Child; D002657:Child Development / Q000502:physiology*; D002659:Child Development Disorders, Pervasive / Q000453:epidemiology / Q000235:genetics*; D004200:Diseases in Twins; D004739:England / Q000453:epidemiology; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D014852:Wales / Q000453:epidemiology
autism spectrum disorder; autistic traits; behavior genetics; longitudinal