The British Journal of Psychiatry (2009) 195: 531-536. doi: 10.1192/bjp.bp.108.060889
© 2009 The Royal College of Psychiatrists
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Data supplement
Right arrow A correction has been published
Right arrow Submit an eLetter
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via CrossRef
Right arrow Citing Articles via Google Scholar
Right arrow Citing Articles via Scopus
Google Scholar
Right arrow Articles by Hoekstra, R. A.
Right arrow Articles by Ronald, A.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Hoekstra, R. A.
Right arrow Articles by Ronald, A.

Association between extreme autistic traits and intellectual disability: insights from a general population twin study

R. A. Hoekstra, MSc, PhD

Autism Research Centre, Department of Psychiatry, University of Cambridge, Cambridge, and Department of Life Sciences, The Open University, Milton Keynes

F. Happé, BA(Hons), PhD

Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, King’s College, London

S. Baron-Cohen, BA(Hons), PhD, FBPsS, MPhil (Clinical Psychology) and A. Ronald, BA(Hons), PhD,

Centre for Brain and Cognitive Development, School of Psychology, Birkbeck College, London, UK.

Correspondence: Correspondence: R. A. Hoekstra, The Open University, Department of Life Sciences, Walton Hall, Milton Keynes, MK7 6AA, UK. Email: R.A.Hoekstra{at}open.ac.uk

Declaration of interest

None.

This paper has been corrected post-publication in deviation from print and in accordance with a printed correction in the July 2010 issue.

Background

Autism is associated with intellectual disability. The strength and origin of this association is unclear.

Aims

To investigate the association between extreme autistic traits and intellectual disability in children from a community-based sample and to examine whether the association can be explained by genetic factors.

Method

Children scoring in the extreme 5% on measures of autistic traits, IQ and academic achievement were selected from 7965 7/8-year-old and 3687 9-year-old twin pairs. Phenotypic associations between extreme autistic traits and intellectual disability were compared with associations among the full-range scores. Genetic correlations were estimated using bivariate DeFries–Fulker extremes analyses.

Results

Extreme autistic traits were modestly related to intellectual disability; this association was driven by communication problems characteristic of autism. Although this association was largely explained by genetic factors, the genetic correlation between autistic traits and intellectual disability was only modest.

Conclusions

Extreme autistic traits are substantially genetically independent of intellectual disability.