Misleading Trends of Changing Autism Prevalence
If statistics compiled by the U.S. Department of Education are to be believed, in 1992 the state of Illinois had only 322 diagnosed cases of autism among school children. In 2003, according to the same statistical source, Illinois had more than 6,000 children diagnosed as autistic.
National special education statistics, which showed a 657 percent increase in autism over the decade from 1993 to 2003, are routinely used to suggest the country is experiencing an epidemic of autism, a developmental disorder of children characterized by impaired social and communication skills as well as repetitive behaviors and obsessive interests.
But inconsistencies in how the condition is diagnosed throughout the nation's schools, and the fact that the increasing trend for autism coincides with a corresponding slump in the reporting of mental retardation and learning disabilities, challenges the use of special education data to portray a national epidemic of autism, according to a new study published in the current issue of a leading medical journal (April 3, 2006).
Paul Shattuck, a researcher at the University of Wisconsin-Madison's Waisman Center, writing in Pediatrics, says special education data cannot be used to claim there is an autism epidemic because the figures are "hopelessly confounded" by changing and uneven identification and reporting practices among schools and states.
At issue, says Shattuck, is the practice of "diagnostic substitution," where educators, over time, have increasingly applied the autism label to children who, in the past, would have been labeled differently.