The flood of kids with autism pouring into special education classes doesn't mean we're in the middle of an autism epidemic, a new study suggests.
A new report in the April issue of Pediatrics suggests that the increase in autism may be due to improved diagnostics that have led to children who would previously have been diagnosed with mental retardation or learning disabilities being diagnosed with autism.
Experts hotly debate the issue of whether there really are more autistic kids than there used to be. Many parents worry that there may be something out there that's causing autism. Fueling their fears is a huge explosion in the number of autism cases pouring into state-funded programs.
This explosion in the need for special autism education might be because there's more autism than ever before. Or it might be because we're getting better at diagnosing autism -- and because treatment is getting better, drawing more kids into special-education classes at earlier ages.
Advocates of the autism-epidemic theory point to a recent California study. Those researchers found little evidence that changes in autism diagnosis affected how many kids have autism. And while they defend their findings, the study has come under fire from other autism experts.
The new study looks at data from across the U.S. It shows that what's true for California and a handful of other states isn't true for the nation as a whole. The increase in autism is offset by a decrease in mental retardation and learning disabilities, finds University of Wisconsin, Madison, researcher Paul T. Shattuck, PhD.
"Many of the children now being counted in the autism category would probably have been counted in the mental retardation or learning disabilities categories if they were being labeled 10 years ago instead of today," Shattuck says in a news release.
And that's not the only reason why special-education statistics are misleading.
"Schools didn't start counting kids with autism until the early 1990s," Shattuck tells WebMD. "Current counts [of autistic kids in special-ed classes] are still below what the true [autism] prevalence is. And if you take into consideration that counts of special kids in other categories declined at a rate corresponding to the increase in the autism rate, then all of a sudden those special-ed trend lines don't look so worrisome."
Despite the explosion in the enrollment of autistic kids in special-education classes, Shattuck says there are still a lot of autistic kids who aren't getting these services.
"We should expect special-education trends in most states to continue going up in the foreseeable future because most state special-ed counts are significantly underestimating the number of kids who actually have autism," he says.
Autism's Shifting Shape
Why is it so hard to tell whether there is an autism epidemic? There are several reasons. One is that autism isn't one thing. It's a spectrum of disorders, with different (unknown) causes, different (unknown) risk factors, and different (unknown) genetic predispositions.
And what one state special-ed program calls autism differs from the definition used by another state. Shattuck says these different definitions make it a "hopeless" task to try to use special education enrollment to measure autism.
"I think parents and advocates have every right to be angry at our collective inability to answer such consequential questions as, 'Do more of our children have autism than in the past? If yes, then why?'" he says.
An accompanying editorial takes issue with one of Shattuck's main conclusions. It's written by Craig J. Newschaffer, PhD, director of the Center for Autism and Developmental Disabilities Epidemiology at Johns Hopkins Bloomberg School of Public Health.
In a 2005 study, Newschaffer and colleagues concluded that shifting diagnostic categories can't account for the increase in autism cases. Newschaffer's data suggested some increase in autism cases.
"There are two major hypotheses about this," Newschaffer tells WebMD. "One is that something is going on that increases children's risk of autism. The other is that the increased number of cases is due to changes in the autism diagnosis and an increased tendency to diagnose autism instead of something else."
In his editorial, Newschaffer notes that we don't know the cause of autism. That means autism diagnosis has to be made on the basis of a child's behavior, not a child's biology. And look-back studies simply aren't a sharp enough tool to unearth, once and for all, whether autism was as common in the past as it is now.
"There strong beliefs on both sides of the issue," Newschaffer says. "But if you try to get objective and sit back -- if you try to be honest -- I don't think the data are valid, precise, or good enough to tease these things out."
A new CDC study is trying to unravel the issue. But Newschaffer thinks this isn't likely to provide definitive answers.
"We are not likely to develop a conclusive body of evidence to either fully support or fully refute the notion that there has been some real increase in autism risk over the past two decades," he writes.
By Daniel J. DeNoon, reviewed by Louise Chang, MD
SOURCES: Shattuck, P.T. Pediatrics, April 2006; vol 117: pp 1028-1037 and 1438-1439. Newschaffer, C.J. Pediatrics,April 2006; vol 117: pp 1436-1437. Newschaffer, C.J. Pediatrics, March 2005; vol 115: pp 277-282. News release, University of Wisconsin.Paul T. Shattuck, PhD, research associate, University of Wisconsin, Madison. Craig J. Newschaffer, PhD, associate professor and director, Center for Autism and Developmental Disabilities Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore.