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Any discussion of an autism epidemic should take account of Wing (1993) The Definition and Prevalence of Autism: A Review. European Child and Adolescent Psychiatry, Vol.2, Issue 2, April 1993, pp.61-74. It is available online with permission from the publishers. http://www.mugsy.org/wing.htm

Wing discusses a number of factors that might explain the differences in prevalence across the sixteen studies she examines. Case finding was one difference. Studies that relied on psychiatric records to identify cases produced the lowest rates. Studies where the entire population including normally developing children were screened produced the highest results. Diagnostic criteria mattered as well. Early studies used a lack of social interaction. Later studies referred too impairment rather than absence. Wing herself illustrates this factor in the Camberwell Study (J Wing L, Gould J.
Severe impairments of social interaction and associated abnormalities in children: epidemiology and classification.Autism Dev Disord. 1979 Mar;9(1):11-29.) Using strict criteria from Lotter's original epidemiological study they found a similar rate of 4-5 in 10000. When they included children who also identified a larger group of children (about 15 per 10,000) who had impairments of social interaction,
communication and imagination (which they referred to as
the 'triad' of impairments), together with a repetitive stereotyped pattern of activities. Although these children did not fit into the full picture of early childhood autism (or typical autism) as described by Kanner they were identified as being within the broader 'autistic spectrum'.

So, in the UK in children with an IQ less than 70 we had a rate of 1 in 500 in 1979 for autistic spectrum disorder. The only study that ever found anything approaching 1 in 10000 was in North Dakota (Burd, L., Fisher, W. & Kerbeshian, J. (1987). A prevalance study of pervasive developmental disorders in North Dakota Journal of the American Academy of Child and Adolescent Psychiatry, 26, 704-710. ) They used the highly restrictive DSM III criteria and found 1.2 in 10000 for infantile autism. But their overall figure, including childhood onset (after 30 months) and Atypical Pervasive Developmental Disorder, was 3.3 in 10000.

When you include children of normal intelligence being educated in mainstream schools, so called high functioning and Asperger types, the combined figure for prevalence is around 1 in 100. That is not to say there has been no increase. There may well have been. Existing studies cannot settle that question. But there is a paucity evidence for a massive increase and talk of an epidemic has no justification at all.

Mike Stanton

September 11, 2011 - 3:33pm

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