Environmental Influences May Cause Autism: Children of Older Mothers at Risk

Could environmental influences cause autism? That's exactly what scientists have found in this latest study. They've discovered that some cases of autism spectrum disorder (ASD) can result from environmental influences rather than gene mutations.

About one in 68 children in the U.S. have an ASD, which is a 30 percent rise from one in 88 just two years ago. While a large number of people with an ASD have gene mutation that are responsible for their conditions, a number of studies involving identical twins in which one has an ASD and the other doesn't reveals that not all ASD cases are caused by mutations. Instead, they could also be caused by environmental conditions.

In order to learn a bit more about what environmental conditions spur the development of autism, the researchers examined 47 children with an ASD and 48 typically developing children of women who were 35 and over. More specifically, the scientists examined the buccal epithelial cells that line the cheek in order to see if genetic differences existed.

"We hypothesized that whatever influences lead to ASD in children of older women probably are already present in the reproductive cells that produce the embryo or during htevery earliest stages of embryonic development-in cells that give rise to both the buccal epithelium and the brain," said John Greally, one of the researchers, in a news release. "This would mean that whatever abnormalities we found in the cheek cells of children with an ASD versus TD children should exist in their brain cells as well."

The scientists found no genetic differences, so then they examined the cells for evidence of environmental effects.  In the end they found two groups of genes that were epigenetically distinctive in children with ASD, which hinted that environmental forces were at play.

"In the case of older mothers at risk for having children with ASDs, one possible environmental influence could be the aging process itself, which could disturb epigenetic patterns in their eggs, but there are other possibilities as well," said Greally in a news release. "Although much work is needed, our study reveals a plausible way that environmental influences-which we know are important in ASD-might be exerting their effects."

The findings are published in the journal PLOS Genetics.