An epidemic of autism?

Leigh MacMillan, Ph.D.
Published: November, 2003

In California, the number of individuals with autism spectrum disorders seems to be spiraling upward, from 10,000 to 20,000 cases between 1999 and 2002. California is not alone. Other states are seeing similar climbs, prompting parents and some researchers to argue that the country is experiencing an epidemic of autism.

The numbers would seem to bear that out. The few epidemiological studies conducted in the United States in the 1980s and early 1990s reported low prevalence rates, approximately four cases of autism per 10,000 children. A study published this year cited a prevalence rate of 34 cases per 10,000—nearly 10 times higher than the earlier studies—in children in the metropolitan Atlanta area. Studies in other parts of the world are turning up rates as high as 60 per 10,000.

One explanation for an increase in cases, investigators say, is that the diagnostic criteria for autism have changed. The autistic spectrum now includes high-functioning individuals who would not have been diagnosed with autism a decade ago. But parents like Tammy Vice, whose daughter Morgan has Asperger disorder, don’t buy it. “You would not have missed these kids; they’re very different, very unique,” she says.

“Subjectively speaking, there do seem to be more children with autism than years ago,” says Wendy L. Stone, Ph.D., professor of Pediatrics and Psychology, and an investigator in the Vanderbilt Kennedy Center for Research on Human Development. “I know for sure that the diagnostic criteria have changed to include the milder forms of autism and there’s greater awareness, but I would not rule out the possibility that there has been an increase in the prevalence of the disorder.”

Is something in the environment to blame? Although childhood vaccines have been fingered as potential culprits, there’s no good evidence that vaccines are responsible for the apparent increase in the diagnosis of autism, says Jonathan L. Haines, Ph.D., director of Vanderbilt’s Program in Human Genetics and a Kennedy Center investigator. “But we certainly have a lot of junk in the environment that wasn’t there 30 years ago,” he says. “If we could figure out what the autism trigger is and stop it, that would be fantastic.”

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