"The analysis, which runs counter to decades of research, says environmental factors may be more important than genes in determining whether a child develops autism," reports the Los Angeles Times, adding, "The conclusion is roundly criticized by other autism experts."
According to the article, "Environmental factors may be more important than genes in determining whether a child develops autism, according to a controversial new analysis of the disorder in twins. That finding runs counter to decades of prior research, which has generally found that genetic inheritance is the biggest determinant of a child’s risk of autism. The authors of thenew study, published online Monday, July 4, 2011, by the journal Archives of General Psychiatry, came to their conclusion after studying 192 pairs of identical and fraternal twins in which at least one twin met clinical criteria for the neurodevelopment disorder."
The story notes, "The study authors acknowledged that their calculations were subject to a wide margin of error and thus could be incorrect. Still, they said that the analysis highlights the need for more research into environmental factors that may contribute to autism. ‘Genetics don’t explain it,’ said coauthor Neil Risch, a genetic epidemiologist at UC San Francisco. ‘They’re part of the story, but only part of the story.’ "
Reaction of one expert, according to the article: " ‘It’s a massive claim,’ said Angelica Ronald, a behavior geneticist at Birkbeck University of London. ‘It flies in the face of the previous data. I don’t see why the results have come out the way they have.’ "
According to the LA Times article, the new study found that "For boys with any form of autism — the biggest group in the sample — the researchers found concordance rates of 77% for identical twin pairs and 31% for fraternal twin pairs. Those figures were in line with other recent studies. Then they plugged those figures into a computer model that used statistical methods to account for the contributing roles of genetics, environmental factors that were shared by both twins and other environmental influences that weren’t shared. They calculated that 38% of the risk for autism came from genes and 58% came from the environment that twins shared."