The author of this paper admits he was surprised by the findings. Before this study, scientists estimated that genes accounted for 90 percent of autism risk and only 10 percent was attributed to non-genetic environmental factors. Now, this Stanford study shows almost the opposite.
Kevin Epstein has always suspected there could be non-genetic factors in autism. His son Elliot is nearly 6 years old and was diagnosed several years ago.
"Those of us who have children like this, on the one side hope hugely to find a cure or at least a cause so that fewer and fewer children are subjected to this," said Epstein.
A new study out of Stanford suggests environmental factors must also be involved. Nearly 200 sets of twins were assessed. Keep in mind that identical twins share the same set of genes -- so if one twin has a disorder, the other one will too.
"So basically one has autism, then the other one also has autism," said Dr. Joachim Hallmayer.
Based on past studies, Hallmayer knew that wasn't always true with identical twins or with fraternal twins who share 50 percent of their genes.
But his study -- the largest ever of twins -- proved environmental factors played a larger role than previously thought. His study concluded that genes account for 38 percent of autism risk while the environment accounts for 62 percent.
So what environmental risk factors are they talking about? That's the big unknown. But what they seem to know is that something could be happening very early on or doing the pregnancy.
"Things that affect the pregnancy, medication during pregnancy, toxins during pregnancy, infection during pregnancy, things like this I would start to look at," said Hallmayer.
Epstein would like to see more research that could identify both genetic and environmental triggers
"More would be better. More funding more studies, better insurance coverage, everyday is a battle," said Epstein.
For years, studies have focused on childhood vaccines as a possible trigger. Hallmayer says there is very little evidence to support that. He believes researchers should move on and study other environmental factors.