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Autism is Caused by Environmental Factors -- Maybe
Food allergies, once discredited as a cause of autism, are making a comeback. So is exposure to chemicals, bacterial infections and other environmental factors.
"Genetics don't explain it," researcher Neil Risch, a genetic epidemiologist at UC San Francisco, tells the Los Angeles Times. "They're part of the story, but only part of the story."
Other research has largely ruled out environmental factors, but Risch and his colleagues still think they may be responsible for autism.
"I think they're really on shaky ground to say that," Paul Law, the director of the Interactive Autism Network at the Kennedy Krieger Institute in Baltimore, tells the Los Angeles Times.
"It's a massive claim," echoes Angelica Ronald, a behavior geneticist at Birkbeck University of London. "It flies in the face of the previous data," she tells the Times. "I don't see why the results have come out the way they have."
Risch and his team resurrected environmental causes after studying 192 pairs of identical and fraternal twins with at least one of the twins having autism. The researchers admit their calculations provide a wide margin for error. Still, they insist environmental factors deserve a fresh look.
So what really causes autism? Pick a card, any card.
The Times reports the condition used to be blamed on detached, unemotional "refrigerator mothers." After a study of twins in the 1970s, it became regarded as a genetic disorder. When the number of autism diagnoses began exploding in the '90s, it was blamed on everything from childhood vaccines to over-reactive doctors and parents.
Scientists have all but given up on finding a smoking gun that can explain large numbers of autism cases, the Times reports. Instead, they are looking for multiple risk factors that each have small effects. But the smaller the risk, the paper reports, the more difficult it is to find.
Autism researcher Lisa Croen, an epidemiologist who heads Kaiser's Autism Research Program in Oakland, tells the Times one thing is certain: "We can't determine causation from one study."
Start by teaching him that it is safe to do so.