Special education data provide misleading trends of changing autism prevalence

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http://www.eurekalert.org/pub_releases/2006-04/uow-sed033006.phpPublic release date: 3-Apr-2006Contact: T. ShattuckShattuck@...608-890-0752University of Wisconsin-MadisonSpecial education data provide misleading trends of changing autismprevalenceMADISON - If statistics compiled by the U.S. Department of Education areto be believed, in 1992 the state of Illinois had only 322 diagnosedcases of autism among school children. In 2003, according to the samestatistical source, Illinois had more than 6,000 children diagnosed asautistic.National special education statistics, which showed a 657 percentincrease in autism over the decade from 1993 to 2003, are routinelyused to suggest the country is experiencing an epidemic of autism, adevelopmental disorder of children characterized by impaired social andcommunication skills as well as repetitive behaviors and obsessiveinterests.But inconsistencies in how the condition is diagnosed throughout thenation's schools, and the fact that the increasing trend for autismcoincides with a corresponding slump in the reporting of mentalretardation and learning disabilities, challenges the use of specialeducation data to portray a national epidemic of autism, according to anew study published in the current issue of a leading medical journal(April 3, 2006). Shattuck, a researcher at the University of Wisconsin-Madison'sWaisman Center, writing in Pediatrics, says special education datacannot be used to claim there is an autism epidemic because the figuresare "hopelessly confounded" by changing and uneven identification andreporting practices among schools and states.At issue, says Shattuck, is the practice of "diagnostic substitution,"where educators, over time, have increasingly applied the autism labelto children who, in the past, would have been labeled differently."My research indicates that the increase in the number of kids with anautism label in special education is strongly associated with adeclining usage of the mental retardation and learning disabilitieslabels in special education during the same period," Shattuck says."Many of the children now being counted in the autism category wouldprobably have been counted in the mental retardation or learningdisabilities categories if they were being labeled 10 years ago insteadof today."The point, says Shattuck, is that identification and diagnosticpractices change over time and can lead to a misperception that acondition is more prevalent than it has been in the past."Each year since 1994, the probability of using the autism label hasincreased while there has been a corresponding decrease in thelikelihood of educators using the mental retardation and learningdisabilities categories."In contrast to the dominant pattern, California was found to be one ofonly a handful of states where there was no decrease in the number ofchildren labeled mentally retarded corresponding with an upward trendin identification of autism. This undermines the use of data coming outof California as a representative indicator of what is happening in therest of the country, as has been suggested in recent press accounts andofficial reports, Shattuck argues.In the U.S., federal law mandates the provision of special education inthe nation's schools. Schools are required to provide specializedservices to children identified as having special needs and they mustclassify individuals according to 13 specified categories for the sakeof annual enrollment reports. Autism was only added to the list in theearly 1990s, and the federal statute's definition of the condition,amounting to just a few sentences, is vague, Shattuck says.What's more, there are no uniform diagnostic practices or guidelinesamong states or school districts, meaning that how children arediagnosed and sorted in special education settings can varydramatically from school to school."Schools nationwide don't adhere to any common diagnostic guidelineswhen they're sorting kids into these categories," Shattuck explains."States and individual schools are left to devise criteria. Everyone isusing a different yardstick to measure the same thing."Shattuck notes that the diagnostic methods employed by schools inspecial education settings are distinct from medical and psychologicaldiagnoses of autism, which entail a more precise definition of thecondition and uniform diagnostic methodologies. Lord, an expert on autism at the University of Michigan, notedthat the new study has important implications for understanding the linkbetween the everyday lives of children with autism and the ways thecondition is identified and labeled in schools. "Shattuck's work hasboth theoretical and practical importance. It highlights the need toconsider the immediate implications for children's lives of the lagbetween scientific findings regarding the diagnosis and prevalence ofautism, and state and school system policies," Lord says.Shattuck emphasized that his study does not show, one way or another,whether there is an epidemic of autism. His study, he says, only showsthat trends from special education data are insufficient to make such adetermination, as is commonly done."The upshot is that it is not valid to conclude there is an epidemic ofautism by looking to special education data, because the specialeducation data is plagued with this diagnostic substitution phenomenonand the lack of nationally uniform diagnostic procedures."Shattuck says his study reveals, among other things, a nationalinability to accurately measure the scope of developmental disabilityamong Americans."In fact, we simply do not have an adequate infrastructure of publichealth data in this country to say one way or another whether the trueprevalence of autism has changed in the general population since theearly 1990s. And this study emphasizes why it is so important tocontinue funding the longitudinal study of prevalence in severalstates, funded by the Centers for Disease Control, that beganrecently," he says."It is in the absence of good quality information that peopleunderstandably make the mistake of looking to the special educationdata to draw conclusions. And I think parents and advocates have everyright to be angry at our collective inability to answer suchconsequential questions as, 'Do more of our children have autism thanin the past? If yes, then why?' "###Shattuck's research was supported by a grant from the National Instituteof Child Health and Human Development.CONTACT: T. Shattuck, (608) 890-0752, Shattuck@...Editor's Note: Shattuck is most easily be reached by e-mail.