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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.

Autism: A True Increase or Semantics? continued...

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 mentally retarded. "Today the minority of kids [with ASD] are mentally retarded,'' 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.

"This is harder than cancer because in cancer you can biopsy it; you can see it on an X-ray," Goldstein says. "We don't have a blood test [for autism]. There is no biomarker, no image, no pathology."

"There won't be one single explanation,'' says Marvin Natowicz, MD, PhD, a medical geneticist and vice chairman of the Genomic Medicine Institute at the Cleveland Clinic.

"There's been a lot of progress in the last few years in terms of understanding the causes of autism," Natowicz says. "We know a lot more than we did." Still, he says, research has a long way to go. "One number you see often is that about 10% of those with autism have a definitive diagnosis, a causative condition." The other 90% of cases are still a puzzle to the experts.

Often, a child with autism will have a co-existing problem, such as a seizure disorder, depression, anxiety, or gastrointestinal or other health problems. At least 60 different disorders -- genetic, metabolic, and neurologic -- have been associated with autism, according to a report published in The New EnglandJournal of Medicine.

On one point most agree: A combination of genetics and environmental factors may play a role. Scientists are looking at both areas.

Zeroing In on the Genetics of Autism

Some evidence that genetics plays a role in autism and ASD is provided by research on twins. According to the CDC, if one identical twin has autism, there's a 75% chance the other twin will be affected, too. If a fraternal twin is affected, the other twin has a 3% chance of having autism.

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