Inside the Autistic Mind

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At the Center for Children's Environmental Health and Disease Prevention at the University of California at Davis, toxicologist Isaac Pessah is studying hair, blood, urine and tissue samples from 700 families with autism. He's testing for 17 metals, traces of pesticides, opioids and other toxicants. In March Pessah caused a stir by releasing a study that showed that even the low level of mercury used in vaccines preserved with thimerosal, long a suspect in autism, can trigger irregularities in the immune-system cells--at least in the test tube. But he does not regard thimerosal (which has been removed from routine childhood vaccines) as anything like a smoking gun. "There's probably no one trigger that's causing autism from the environmental side," says Pessah, "and there's no one gene that's causing it."

Indeed, most researchers believe autism arises from a combination of genetic vulnerabilities and environmental triggers. An identical twin of a child with autism has a 60% to 90% chance of also being affected. And there's little doubt that a vulnerability to ASD runs in some families: the sibling of a child with autism has about a 10% chance of having ASD. Gene scientists working on autism have found suspicious spots on chromosomes 2, 5, 7, 11 and 17, but there are probably dozens of genes at work. "We think there are a number of different autisms, each of which could have a different cause and different genes involved," says David Amaral, research director of the MIND (Medical Investigation of Neurodevelopmental Disorders) Institute, also at U.C. Davis.

Amaral is heading MIND's efforts to assemble a database of clinical, behavioral and genetic information on 1,800 autistic kids. One goal is to clearly define autism subtypes. "It's hard to do the genetics if you're talking about four or five different syndromes," says NIMH chief Insel. "Does the presence of seizures define a separate illness? What about the kids who seem to develop normally for the first year and a half and then regress--is that a separate thing?" And what about the large number of autistic kids who have serious gastrointestinal problems and the many with immune dysfunctions--are they distinct subtypes?

Amaral and colleague Judy Van de Water believe they are onto a major discovery about the origins of at least one type of autism--a strongly familial variety. They have detected aberrant antibodies in the blood of kids from families with a pattern of ASD and, significantly, in mothers with more than one autistic child. "These antibodies are actually raised against proteins in the fetal brain," says Amaral, who recently submitted a paper on the discovery. The working hypothesis is that these antibodies may alter brain development in ways that lead to autism. If correct, the finding could lead to a maternal blood test and the use of a therapy called plasmapheresis to clear antibodies from the mother's blood. "You get a sense of the excitement," says Amaral, "if you could prevent, say, 20% of kids from getting autism. But we don't want to raise false hopes."

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