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 the new study, published online Monday 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.
But the authors' conclusion that environmental influences — perhaps chemical exposures, infections, diet or stress levels — could be so influential was roundly criticized by other autism experts.
"I think they're really on shaky ground to say that," said Dr. Paul Law, director of the Interactive Autism Network at the Kennedy Krieger Institute in Baltimore.
"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."
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."
Shirley S. Wang writes in The Wall Street Journal:
A preliminary but provocative new study finds women who take antidepressants during pregnancy have a moderately higher risk of having a child with autism, according to a paper published in the Archives of General Psychiatry.
The research on antidepressants and autism is thought to be the first to look for and identify such a link. Results indicated a doubling in risk of autism if the mother filled a prescription for antidepressants at any point in the year before delivery. The risk tripled if she filled the prescription during the first trimester of pregnancy.
The findings don't speak to whether antidepressants cause autism, and the work needs to be replicated, the authors cautioned. The data, though, do indicate that the drugs have "possible adverse outcomes in children" and deserve further study, said Lisa Croen, first author on the study and an epidemiologist in the research division of Kaiser Permanente Northern California, the big managed-health plan.