A new study by Stanford University researchers suggests that exposure to chemicals may be fueling America’s growing rate of autism; a developmental disorder that now effects in in every 110 children in the U.S. and one in seventy boys.
According to an announcement about the study from Stanford “From prior studies of shared autism in twins, scientists had estimated that 90 percent of autism risk was attributable to genes and only 10 percent to non-genetic environmental factors. But the new study — the largest ever of twins in which at least one in each pair has autism — shows almost the opposite: It found that genes account for 38 percent of autism risk, with environmental factors explaining the remaining 62 percent. ” Prior to the study, headed up by Neil Risch, PHD, professor of biostatistics at UC-San Francisco and director of the UCSF Institute for Human Genetics, scientists had believed that 90% of a child’s risk of developing autism stemmed from their genes.
Joachim Hallmayer, MD, associate professor of psychiatry and behavioral sciences at Stanford, was surprised by the results of the study. ” Environmental factors play a bigger role than previously thought. Our research shows us that we need to be studying both genetic and environmental factors as well as how they interact with each other. We need to explore areas of environmental risk that are shared by both twin individuals and impact the development of the child. It took me a bit by surprise that the heritability of autism was so much lower than previous studies calculated. Our work suggests that the role of environmental factors has been underestimated. We have to study both the genetics and the environment. If we look only at one side, I don’t think that will lead us to the right answer.” Hallmayer said .
Linda Lotspeich, MD, clinical professor of psychiatry and behavioral sciences at Stanford and a child and adolescent psychiatrist who works with children with autism, also reminds the public that despite the study’s link to environmental influences, that genes still play a part in the development of autism. scientists have yet to discover which gene or genes are involved. She said, “Scientists need to look for environmental factors. But that doesn’t take away the fact that autism also has a genetic component and is still caused by unknown genes.”
What environmental cause is contributing to the rise in Autism? Scientists don’t the answer to that yet, according to Dr. Hallmayer. “That’s the multimillion dollar question. I think a lot about it. Autism’s manifestation in very young children points to something that happens in early life, potentially even during pregnancy”, he said.
Lisa Croen, PhD., senior research scientist and director of the Autism Research Program at the Kaiser Permanente Division of Research, agrees with Hallmayer that future studies should early on in a child’s life to see how the environment can effect the development of autism. “Our findings suggest that events during pregnancy should be a focus for future research into the origins of autism”, Croen said.
The research was funded by grants from the National Institute of Mental Health as well as Autism Speaks, who was one of several who provided assistance to Stanford for the study. Jennifer Phillips, PhD, clinical associate professor of psychiatry and behavioral sciences; research assistants Sue Cleveland and Andrea Torres; the California Department of Public Health; Kaiser Permanente Northern California; UC-Davis and UCSF, also collaborated with Stanford researchers.
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Steenhuysen, Julie , “Environment, not just genetics, at play in autism“, U.S. National Library of Medicine, 7/4/11, 7/8/11