FRIDAY, Feb. 16, 2007 (HealthDay News) -- The release last week of statistics on the prevalence of autism spectrum disorders in American children -- one case in every 150 8-year-olds -- confirmed that the condition is more common now than it was just a decade ago, when estimates ranged anywhere from one in 500 youngsters to one in 166.
But the new statistics -- from a 14-state survey conducted by the U.S. Centers for Disease Control and Prevention -- failed to clear up the mystery of why autism might be striking more and more children with each passing year.
Alison Singer, senior vice president of the nation's leading autism advocacy group, Autism Speaks, said she didn't need the CDC statistics to know that more families are now struggling with the behavioral disorder.
A decade ago, "we didn't have more than year-long waiting lists for places within schools for children with autism," said Singer, whose 9-year-old daughter is autistic. "In fact, we had far fewer schools then for children with autism, because we had far less need. And if you go into any elementary school in the country, you'll see more children with special needs and with autism than you did when I was in elementary school."
Autism spectrum disorders include autism as well as less disabling conditions such as Asperger's syndrome and pervasive developmental disorder (PDD). All of these conditions involve some level of difficulty in communication and socialization, according to the CDC. Some children may also engage in repetitive behaviors, have trouble dealing with changes in routine, and be prone to emotional outbursts. As many as four in 10 children with autism may not speak at all, the CDC says.
The exact causes of autism remain a mystery. "We know that genes are important," said Dr. Bradley Peterson, professor of child psychiatry at Columbia University Medical Center and the New York State Psychiatric Institute in New York City.
On the other hand, he said, "we know that genes aren't the whole story. Unfortunately, in terms of non-genetic or environmental factors, we just don't have very good leads yet."
Theories as to possible environmental culprits are widespread and hotly debated. They have included a variety of infections (including maternal German measles during pregnancy); drugs such as thalidomide and a labor-inducing agent, Pitocin; synthetic compounds such as PCBs and plastics; and food additives.
Two agents -- the mercury-based vaccine preservative thimerosal, and the measles-mumps-rubella (MMR) vaccine -- gained widespread public attention after a 1998 study by British researcher Dr. Andrew Wakefield linked vaccination to a spike in childhood autism cases.
Debate still rages on that front, although two more recent and much larger studies -- one by the U.S. Institute of Medicine and another British/Japanese effort involving more than 30,000 Japanese youngsters -- have turned up no such link.
So, the question remains: Why are more and more parents discovering their child has autism?
Peterson said the CDC statistics may not be as straightforward as they seem.
"Actually, I think the numbers are comparable to what they were 20 years ago," he said. "Twenty years ago, the estimate [of prevalence] was 5.5 to 6 per 1,000 children, and now it's estimated at 6.6 per 1,000."
While the gap between those numbers is substantial, "it is probably not outside of the margin of error," Peterson said. So, it's still possible that the supposed "rise" is merely a statistical artifact.
Singer discounted that notion, however. "It's not really reflective of the reality of the situation," she said, pointing again to the long waiting lines of parents desperate to get their child treatment or proper schooling, problems Singer said didn't exist 10 years ago.
Peterson also pointed to possible changes in "diagnostic trends" to account for rising numbers. For example, "clinically, in the past, people actually thought it was less stigmatizing, and would bring a child greater social services, if they were diagnosed with mental retardation versus autism," he said. That situation has changed with time, however, so more children may be diagnosed with autism now than they were in the past.
Again, Singer challenged that view. "That's a very easy theory to test," she said. In California, she said, "data showed that there was no drop-off in the number of children that were being diagnosed with mental retardation" -- even as reported diagnoses for autism disorders were climbing.
Then there's the theory that parents and physicians have simply gotten better at spotting autistic spectrum disorders -- even in their milder forms.
"Perhaps, for children that we used to call 'odd' or 'quirky', the radar is now much more sensitive to detecting them and providing a syndromic label, one that they might not otherwise have had in the past," Peterson said.
But while it is true that the early detection of autism has improved in recent years, Singer said no parent is in any rush to get their youngster labeled autistic. "Look, no one would want to send their child to a school for children with autism if they didn't have to," she said. "The demand for those schools, the demand out there for therapists -- all of it points to a true increase."
And yet neither expert was ready to point the finger at any one cause for the increase, environmental or otherwise.
Asked about the MMR/thimerosal debate, Singer said only that, "we continue to focus on the need to cast a very wide net when it comes to autism research. We are not ready say that it's 100 percent genetic or environmental. We simply don't know enough to say what it is or is not."
She remains optimistic that dedicated research will bring real answers.
In December, groups like Autism Speaks helped push the Combating Autism Act through to final approval in Congress. The act authorizes that $945 million be spent over the next five years to unravel the root causes of the disorder.
"Now we need to get that money appropriated," Singer said.
She and Peterson agreed that research is the only way to understand what's driving any rise in autism cases -- and how to turn that trend around.
"We are only going to find real answers in the laboratory," Singer said. "We have to fund scientists who are looking at the biology, looking at what causes autism, who are looking at environmental exposures, looking at the genetics. That's where we are going to find the answers."
More information
To learn more about autism, visit the U.S. National Institute of Mental Health.
