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

  • R. A. Hoekstra (a1), F. Happé (a2), S. Baron-Cohen (a3) and A. Ronald (a4)
Abstract
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.

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Copyright
Corresponding author
R. A. Hoekstra, The Open University, Department of Life Sciences, Walton Hall, Milton Keynes, MK7 6AA, UK. Email: R.A.Hoekstra@open.ac.uk
Footnotes
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The Twins Early Development Study is funded by MRC grant G0500079 to Professor Robert Plomin. R.A.H. is financially supported by the Netherlands Organisation for Scientific Research (NWO Rubicon).

Declaration of interest

None.

Footnotes
References
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  • ISSN: 0007-1250
  • EISSN: 1472-1465
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Association between extreme autistic traits and intellectual disability: insights from a general population twin study

  • R. A. Hoekstra (a1), F. Happé (a2), S. Baron-Cohen (a3) and A. Ronald (a4)
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