Some facts on ASD.
Autism Cases on the Rise; Reason for Increase a Mystery
Scientists are scouring genetic and evironmental data to find a cause for the rise in autism.
By Kathleen Doheny
FROM THE WEBMD ARCHIVES
The number of children diagnosed with autism or related disorders has grown at what many call an alarming rate. In the 1970s and 1980s, about one out of every 2,000 children had autism.
Today, the CDC estimates that one in 150 8-year-olds in the U.S. has an autism spectrum disorder, or ASD. This expanded definition refers not only to autism but also to a collection of brain development disorders such as Asperger's syndrome and a condition known as pervasive developmental disorder -- not otherwise specified (PDD-NOS). Though all the disorders share some symptoms, they are different in other ways, including the timeline of symptoms and the severity, according to the CDC.
The apparent rise in cases triggers two burning questions for parents, physicians, and scientists:
Is autism truly on the rise, or do the new statistics simply reflect the growing awareness of the condition, the expanded definition, and other factors?
If autism is on the rise, as most experts believe, what is causing the increase?
Autism: A True Increase or Semantics?
The jump in autism cases has spawned not only alarm but also debate about whether the number of children with autism could have increased that much in a relatively brief time.
"There's a lot of controversy about that," says Jeff Milunsky, MD, director of clinical genetics and associate director of the Center for Human Genetics at Boston University.
Two researchers who tracked the rate of autism in children born in the same area of England from 1992 to 1995 and then from 1996 to 1998 found that the rates were comparable, and concluded that the incidence of autism was stable. The study was published in the American Journal of Psychiatry in 2005.
But, Milunsky says, several studies have documented an increase in the U.S.
In a recent report in the journal Archives of Disease in Childhood, Milunsky and his colleagues point to several studies finding an increase in autism rates. In 2003, for instance, a large study conducted in Atlanta found that one in 166 to one in 250 children had autism, according to a report published in the Journal of the American Medical Association.
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Another study conducted by the CDC in 14 states found an overall prevalence of one in 152, which Milunsky and others say is the generally accepted figure today.
Other experts say autism is on the increase but that factors other than more children being diagnosed play a role. Some of the increase in reported cases is because of "diagnostic substitution," says Paul Shattuck, PhD, assistant professor of social work at Washington University in St. Louis and an autism researcher.
"A kid labeled autistic today could have been labeled mentally retarded 10 years ago in the same school system," Shattuck says. It wasn't until 1992 that schools began to include autism as a special education classification.
Today, children diagnosed as having autism spectrum disorder are often more mildly affected than the classic "Rain Man" stereotype some people associate with the disorder, Shattuck says. After autism was first identified in 1943, some of the first studies found most of the children intellectually disabled. "Today the minority of kids [with ASD are intellectually disabled],'' Shattuck tells WebMD.
The debate about whether the reported increase in autism is affected by factors such as more awareness misses the point, says Isaac Pessah, PhD, a professor of toxicology, director of the Center for Children's Environmental Health Sciences, and a member of the MIND Institute at the University of California Davis. Rather than argue about whether the increase is because of some children being reclassified or other factors, he says, "We need to understand why it's one in 150."
Focusing on the actual numbers -- rather than the debate -- is wise, says Craig Newschaffer, PhD, chairman and professor of the department of epidemiology and biostatistics at Drexel University School of Public Health in Philadelphia. "We thought autism was a very rare occurrence, and it's clear that it's not."
Getting to the Causes of Autism
Getting to the cause -- or, more accurately, causes -- of autism will be more difficult than unraveling the causes of cancer, says Gary Goldstein, MD, president and CEO of Kennedy Krieger Institute in Baltimore, a facility that helps children with autism and other developmental disorders.
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