Rise in autism increases calls for awareness

For years, the best-known environmental theory involved childhood vaccines, prompted by a flawed 1998 British study that has been thoroughly discredited. Dozens of later studies have found no link between vaccines and autism.

In the past week, a spate of studies released during National Autism Awareness Month has offered tantalizing new information about potential causes. Research published in the journal Nature widened the understanding of the genetic roots of some cases and confirmed the elevated risks for children with older fathers. Another study, released online in Pediatrics, suggested maternal obesity may play a role.

“I do think over the next three to five years we’ll be able to paint a much clearer picture of how genes and environmental factors combine” to cause autism, said Geraldine Dawson, a psychologist who is chief science officer for the advocacy group Autism Speaks.

To be sure, finding the causes of autism—an umbrella term for a variety of disorders that delay children socially or intellectually—remains daunting. The causes are believed to be complicated, and not necessarily the same for each child. Some liken autism to cancer: a small word for a wide range of illnesses. In many cases, autism can be blamed on both genetic problems that load the gun and other factors that pull the trigger.

The lion’s share of money for finding a cause has been spent on genetics, which so far experts believe can account for roughly 20 percent of cases. The earliest success was in the early 1990s and involved the discovery of the genetic underpinnings of Fragile X syndrome, a rare condition that accounts for just 2 to 4 percent of autism cases but is the most common form of inherited intellectual disability in boys.

The focus on genetics has been bolstered by dramatic improvements in gene mapping, as well as the bioengineering of mice with autism symptoms. Dozens of risk genes have been identified, and a half-dozen drug companies are said to be working on developing new treatments.

But even genetics enthusiasts acknowledge that genes are only part of the answer. Studies of identical twins have shown that autism can occur in one and not the other, meaning something outside a child’s DNA is triggering the disorder in many cases. Some cases may be entirely owing to other causes, Dawson said.

That broad “other” category means “environmental” influences—not necessarily chemicals, but a grab bag of outside factors that include things like the age of the father at conception and illnesses and medications the mother had while pregnant.

Studies on the horizon

There also are “association” studies—they don’t prove cause and effect, but merely find connections between certain factors and autism. And sometimes these conclusions can be skewed by other things researchers failed to account for.

Some study results expected within a year:

• Hertz-Picciotto’s study of 1,600 children in Northern California is comparing autistic children, youngsters with other developmental disabilities, and those who have no such diagnoses. Some results have been released already, including the recent finding that suggests a link between autism and a mother’s obesity. An earlier part of the study found that children born to mothers living less than two blocks from a freeway were twice as likely to have autism—presumably because of auto exhaust and air pollution, the researchers speculated.

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