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
"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.