Are Autism Cases on the Rise in U.S.?

FRIDAY, Feb. 16 (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.