Hostname: page-component-7d684dbfc8-jcwnr Total loading time: 0 Render date: 2023-09-28T00:10:02.472Z Has data issue: false Feature Flags: { "corePageComponentGetUserInfoFromSharedSession": true, "coreDisableEcommerce": false, "coreDisableSocialShare": false, "coreDisableEcommerceForArticlePurchase": false, "coreDisableEcommerceForBookPurchase": false, "coreDisableEcommerceForElementPurchase": false, "coreUseNewShare": true, "useRatesEcommerce": true } hasContentIssue false

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

Published online by Cambridge University Press:  19 May 2010

T. Charman*
Centre for Research in Autism and Education, Institute of Education, London, UK
A. Pickles
Division of Epidemiology and Health Sciences, University of Manchester, UK
E. Simonoff
Institute of Psychiatry, King's CollegeLondon, UK
S. Chandler
Centre for Research in Autism and Education, Institute of Education, London, UK
T. Loucas
School of Psychology and Clinical Language Sciences, University of Reading, UK
G. Baird
Guy's and St Thomas' NHS Foundation Trust, London, UK
*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, LondonWC1H 0AA, UK. (Email:



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.


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.


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.


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.

Original Articles
Copyright © Cambridge University Press 2010

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)


Baird, G, Charman, T, Baron-Cohen, S, Cox, A, Swettenham, J, Wheelwright, S, Drew, A (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.CrossRefGoogle Scholar
Baird, G, Simonoff, E, Pickles, A, Chandler, S, Loucas, T, Meldrum, D, Charman, T (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.CrossRefGoogle Scholar
Bertrand, J, Mars, A, Boyle, C, Bove, F, Yeargin-Allsopp, M, Decoufle, P (2001). Prevalence of autism in a United States population: the Brick Township, New Jersey, investigation. Pediatrics 108, 11551161.CrossRefGoogle Scholar
Berument, SK, Rutter, M, Lord, C, Pickles, A, Bailey, A (1999). Autism screening questionnaire: diagnostic validity. British Journal of Psychiatry 175, 444451.CrossRefGoogle ScholarPubMed
Black, DO, Wallace, GL, Sokoloff, JL, Kenworthy, L (2009). Brief report: IQ split predicts social symptoms and communication abilities in high-functioning children with autism spectrum disorders. Journal of Autism and Developmental Disorders 39, 16131619.CrossRefGoogle ScholarPubMed
Bölte, S, Dziobek, I, Poustka, F (2009). Brief report: the level and nature of autistic intelligence revisited. Journal of Autism and Developmental Disorders 39, 678682.CrossRefGoogle ScholarPubMed
Caron, MJ, Mottron, L, Berthiaume, C, Dawson, M (2006). Cognitive mechanisms, specificity and neural underpinnings of visuospatial peaks in autism. Brain 129, 17891802.CrossRefGoogle ScholarPubMed
Carpentieri, S, Morgan, SB (1996). Adaptive and intellectual functioning in autistic and nonautistic retarded children. Journal of Autism and Developmental Disorders 26, 611620.CrossRefGoogle ScholarPubMed
Centers for Disease Control and Prevention (CDC) (2009). Prevalence of autism spectrum disorders – Autism and Developmental Disabilities Monitoring Network, United States, 2006. Morbidity and Mortality Weekly Report. Surveillance Summary 58, 120.Google Scholar
Chakrabarti, S, Fombonne, E (2005). Pervasive developmental disorders in preschool children: confirmation of high prevalence. American Journal of Psychiatry 162, 11331141.CrossRefGoogle ScholarPubMed
Charman, T, Pickles, A, Chandler, S, Wing, L, Bryson, S, Simonoff, E, Loucas, T, Baird, G (2009). Effects of diagnostic thresholds and research versus service and administrative diagnosis on autism prevalence. International Journal of Epidemiology 38, 12341238.CrossRefGoogle Scholar
Charman, T, Taylor, E, Drew, A, Cockerill, H, Brown, JA, Baird, G (2005). Outcome at 7 years of children diagnosed with autism at age 2: predictive validity of assessments conducted at 2 and 3 years of age and pattern of symptom change over time. Journal of Child Psychology and Psychiatry 46, 500513.CrossRefGoogle ScholarPubMed
Dawson, M, Soulières, I, Gernsbacher, MA, Mottron, L (2007). The level and nature of autistic intelligence. Psychological Science 18, 657662.CrossRefGoogle ScholarPubMed
de Bruin, EI, Verheij, F, Ferdinand, RF (2006). WISC-R subtest but no overall VIQ-PIQ difference in Dutch children with PDD-NOS. Journal of Abnormal Child Psychology 34, 263271.CrossRefGoogle ScholarPubMed
Fombonne, E (2009). Epidemiology of pervasive developmental disorders. Pediatric Research 65, 591598.CrossRefGoogle ScholarPubMed
Green, H, McGinnity, A, Meltzer, H, Ford, T, Goodman, R (2005). Mental Health of Children and Young People in Great Britain, 2004. Office for National Statistics (ONS), HMSO: London.CrossRefGoogle Scholar
Happé, FGE (1995). The role of age and verbal ability in the theory of mind task performance of subjects with autism. Child Development 66, 843855.CrossRefGoogle ScholarPubMed
Joseph, RM, Tager-Flusberg, H, Lord, C (2002). Cognitive profiles and social-communicative functioning in children with autism spectrum disorder. Journal of Child Psychology and Psychiatry 43, 807821.CrossRefGoogle ScholarPubMed
Klin, A, Saulnier, CA, Sparrow, SS, Cicchetti, DV, Volkmar, FR, Lord, C (2007). Social and communication abilities and disabilities in higher functioning individuals with autism spectrum disorders: the Vineland and the ADOS. Journal of Autism and Developmental Disorders 37, 748759.CrossRefGoogle ScholarPubMed
Lincoln, AJ, Allen, MH, Kilman, A (1995). The assessment and interpretation of intellectual abilities in people with autism. In Learning and Cognition in Autism (ed. Schopler, E. and Mesibov, G. B.), pp. 89–117. Plenum: New York.CrossRefGoogle Scholar
Liss, M, Harel, B, Fein, D, Allen, D, Dunn, M, Feinstein, C, Morris, R, Waterhouse, L, Rapin, I (2001). Predictors and correlates of adaptive functioning in children with developmental disorders. Journal of Autism and Developmental Disorders 31, 219230.CrossRefGoogle ScholarPubMed
Lord, C, Risi, S, DiLavore, PS, Shulman, C, Thurm, A, Pickles, A (2006). Autism from 2 to 9 years of age. Archives of General Psychiatry 63, 694701.CrossRefGoogle ScholarPubMed
Lord, C, Risi, S, Lambrecht, L, Cook, EH, Leventhal, BL, DiLavore, PC, Pickles, A, Rutter, M (2000). The Autism Diagnostic Observation Schedule-Generic: a standard measure of social and communication deficits associated with the spectrum of autism. Journal of Autism and Developmental Disorders 30, 205223.CrossRefGoogle ScholarPubMed
Lord, C, Rutter, M, Lecouteur, A (1994). Autism Diagnostic Interview-Revised: a revised version of a diagnostic interview for caregivers of individuals with possible pervasive developmental disorders. Journal of Autism and Developmental Disorders 24, 659685.CrossRefGoogle ScholarPubMed
Mayes, SD, Calhoun, SL (2003). Analysis of WISC-III, Stanford-Binet:IV, and academic achievement test scores in children with autism. Journal of Autism and Developmental Disorders 33, 329341.CrossRefGoogle ScholarPubMed
Raven, JC, Court, JH, Raven, J (1990 a). Coloured Progressive Matrices. Oxford University Press: Oxford.Google Scholar
Raven, JC, Court, JH, Raven, J (1990 b). Standard Progressive Matrices. Oxford University Press: Oxford.Google Scholar
Saulnier, CA, Klin, A (2007). Brief report: social and communication abilities and disabilities in higher functioning individuals with autism and Asperger syndrome. Journal of Autism and Developmental Disorders 37, 788793.CrossRefGoogle ScholarPubMed
Schalock, RL, Luckasson, RA, Shogren, KA, Borthwick-Duffy, S, Bradley, V, Buntinx, WHE, Coulter, DL, Craig, EM, Gomez, SC, Lachapelle, Y, Reeve, A, Snell, ME, Spreat, S, Tasse, MJ, Thompson, JR, Verdugo, MA, Wehmeyer, ML, Yeager, MH (2007). The renaming of mental retardation: understanding the change to the term intellectual disability. Intellectual and Developmental Disabilities 45, 116124.CrossRefGoogle ScholarPubMed
Sparrow, S, Balla, D, Cichetti, D (1984). Vineland Adaptive Behaviour Scales. American Guidance Services: Circle Pines, MN.Google Scholar
Stata (2005). Stata Statistical Software Release 9.0: Survey Data Manual. Stata Corporation: College Station, TX.Google Scholar
Tager-Flusberg, H, Joseph, RM (2003). Identifying neurocognitive phenotypes in autism. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 358, 303314.CrossRefGoogle ScholarPubMed
Tsatsanis, KD (2005). Neuropsychological characteristics in autism and related conditions. In Handbook of Autism and Pervasive Developmental Disorders, 3rd edn (ed. Volkmar, F. R., Paul, R., Klin, A. and Cohen, D.), pp. 365381. Wiley: New Jersey.Google Scholar
Volkmar, FR, Lord, C, Bailey, A, Schultz, RT, Klin, A (2004). Autism and pervasive developmental disorders. Journal of Child Psychology and Psychiatry 45, 135170.CrossRefGoogle ScholarPubMed
Wechsler, D (1992). Wechsler Intelligence Scale for Children, Third UK Edition. The Psychological Corporation: London.Google Scholar
WHO (1993). Mental Disorders: A Glossary and Guide to their Classification in Accordance with the 10th Revision of the International Classification of Diseases: Research Diagnostic Criteria (ICD-10). World Health Organization: Geneva.Google Scholar
Yeargin-Allsopp, M, Rice, C, Karapurkar, T, Doernberg, N, Boyle, C, Murphy, C (2003). Prevalence of autism in a US metropolitan area. Journal of the American Medical Association 289, 4955.Google Scholar