As autism cases soar, a search for clues

The findings of the study, published in the January issue of the Archives of Pediatrics and Adolescent Medicine, appear to rule out suspects like vaccinations as a cause for the increase, according to Barbaresi.

Other studies also have failed to link vaccinations to autism, prompting the Institute of Medicine, an independent group that advises the federal government, to conclude there is no connection.

But no one knows exactly what causes ASDs, and until they do, much about these disorders will remain a source of great speculation.

Many unknowns
To say that there’s a lot doctors don’t know about these conditions is “an understatement,” says Dr. Leonard Rappaport, director of the Developmental Medicine Center at Children’s Hospital Boston.

“Most things we don’t know,” he says.

Rappaport suspects there may be a true rise in ASDs, though he says it’s not at all clear why or to what extent.

To better understand the causes, and hopefully improve diagnosis and treatment, Rappaport is involved in a new study that is focusing on genetic underpinnings of the disorders that he says may play a role in upwards of 90 percent of cases. The federal government also has organized an international coalition to explore the genetics.

Many scientists believe that ASDs are largely caused by genes. Studies have shown, for instance, that if one identical twin has autism the second twin is very likely to also have the disorder. But the risk isn't 100 percent, suggesting that other factors can contribute, even if they aren't the main cause.

“I think it’s clear that there’s a strong genetic predisposition,” says Dr. Steve Sommer, chairman of the department of molecular genetics at City of Hope National Medical Center in Duarte, Calif.

One theory behind a cluster of cases of high-functioning autism and Asperger Syndrome in Silicon Valley holds that people who carry the genes gravitate toward high-tech professions like computer science that don't necessarily require a lot of social interaction. And when these people, who may not have the full-blown disorders, meet and have children together, the kids could be fully affected because of the double genetic whammy from both parents.

Down the line, scientists suspect they may find many genes involved in ASDs.

Sommer’s research has shown that a mutation in the neuroligin 4 gene, which is involved in creating healthy connections between neurons in the brain, is defective in about 3 percent of people with autism. But that doesn’t mean that everyone who inherits the defective gene will develop autism, he says. And there are likely many more genes that play a role in the condition in certain people.

“From a genetic point of view, autism is likely to be many — perhaps a hundred or more — diseases,” he says.

Sleepless nights
But if autism spectrum disorders are truly on the rise, genes aren’t the reason. “The gene pool doesn’t change,” explains Rappaport. “It would have to be something that’s environmental.”

That something — if it does exist — remains a huge mystery and a source of endless worry for parents, especially given that there is currently no known way to prevent autism.

Rappaport says many parents fear they may have done something to trigger the problem, like taking their kids to get regularly scheduled immunizations or exposing themselves to environmental toxins.

“Parents are searching for answers, and they’re blaming themselves for a million different things,” he says.

“I can’t even imagine all the sleepless nights.”

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