EBD Blog

Several sources are covering a story about the prevalence of autism. The U.S. Department of Education data released annually have shown the the percentage of school-age children who are identified as having autism has increased dramatically since the early 1990s. The stories cover alternative explanations for those increases.

In an article in Pediatrics called “The Contribution of Diagnostic Substitution to the Growing Administrative Prevalence of Autism in US Special Education,” Paul T. Shattuck, a professor at the University of Wisconsin, Madison (Madison, WI; US) examined the US school prevalence data of autism. He concludes that much of the increase is attributable to schools’ eligibility teams using “autism” instead of “mental retardation” or “Learning Disability” to declare students eligible for special education.

The average administrative prevalence of autism among children increased from 0.6 to 3.1 per 1000 from 1994 to 2003. By 2003, only 17 states had a special education prevalence of autism that was within the range of recent epidemiological estimates. During the same period, the prevalence of mental retardation and learning disabilities declined by 2.8 and 8.3 per 1000, respectively. Higher autism prevalence was significantly associated with corresponding declines in the prevalence of mental retardation and learning disabilities.

Champions of the idea that autism is caused by chemicals present in childhood immunizations often refer to the increased prevalence of autism as evidence for their hypothesis. They reason that the increases are associated with changes in the delivery of vacinations. We can expect expressions of concern from them about this study.

Link to the abstract for Mr. Shattuck’s article. Links to coverage of the story by (so far):

• MedPage
• The Badger Herald (U. Wisc paper)
• Fox