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IQ in children with autism spectrum disorders: data from the Special Needs and Autism Project (SNAP)

  • T. Charman (a1), A. Pickles (a2), E. Simonoff (a3), S. Chandler (a1), T. Loucas (a4) and G. Baird (a5)...
Abstract
Background

Autism spectrum disorder (ASD) was once considered to be highly associated with intellectual disability and to show a characteristic IQ profile, with strengths in performance over verbal abilities and a distinctive pattern of ‘peaks’ and ‘troughs’ at the subtest level. However, there are few data from epidemiological studies.

Method

Comprehensive clinical assessments were conducted with 156 children aged 10–14 years [mean (s.d.)=11.7 (0.9)], seen as part of an epidemiological study (81 childhood autism, 75 other ASD). A sample weighting procedure enabled us to estimate characteristics of the total ASD population.

Results

Of the 75 children with ASD, 55% had an intellectual disability (IQ<70) but only 16% had moderate to severe intellectual disability (IQ<50); 28% had average intelligence (115>IQ>85) but only 3% were of above average intelligence (IQ>115). There was some evidence for a clinically significant Performance/Verbal IQ (PIQ/VIQ) discrepancy but discrepant verbal versus performance skills were not associated with a particular pattern of symptoms, as has been reported previously. There was mixed evidence of a characteristic subtest profile: whereas some previously reported patterns were supported (e.g. poor Comprehension), others were not (e.g. no ‘peak’ in Block Design). Adaptive skills were significantly lower than IQ and were associated with severity of early social impairment and also IQ.

Conclusions

In this epidemiological sample, ASD was less strongly associated with intellectual disability than traditionally held and there was only limited evidence of a distinctive IQ profile. Adaptive outcome was significantly impaired even for those children of average intelligence.

Copyright
Corresponding author
*Address for correspondence: Professor T. Charman, Chair in Autism Education, Centre for Research in Autism and Education, Department of Psychology and Human Development, Institute of Education, 25 Woburn Square, London WC1H 0AA, UK. (Email: t.charman@ioe.ac.uk)
Linked references
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This list contains references from the content that can be linked to their source. For a full set of references and notes please see the PDF or HTML where available.

G Baird , T Charman , S Baron-Cohen , A Cox , J Swettenham , S Wheelwright , A Drew (2000). A screening instrument for autism at 18 month of age: a six-year follow-up study. Journal of the American Academy of Child and Adolescent Psychiatry 39, 694702.

G Baird , E Simonoff , A Pickles , S Chandler , T Loucas , D Meldrum , T Charman (2006). Prevalence of disorders of the autism spectrum in a population cohort of children in South Thames: the Special Needs and Autism Project (SNAP). Lancet 368, 210215.

FGE Happé (1995). The role of age and verbal ability in the theory of mind task performance of subjects with autism. Child Development 66, 843855.

RM Joseph , H Tager-Flusberg , C Lord (2002). Cognitive profiles and social-communicative functioning in children with autism spectrum disorder. Journal of Child Psychology and Psychiatry 43, 807821.

C Lord , S Risi , PS DiLavore , C Shulman , A Thurm , A Pickles (2006). Autism from 2 to 9 years of age. Archives of General Psychiatry 63, 694701.

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Psychological Medicine
  • ISSN: 0033-2917
  • EISSN: 1469-8978
  • URL: /core/journals/psychological-medicine
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