A study in five countries suggests that most of the variation in risk for autism may be explained by genetics rather than differences in environmental, lifestyle or pregnancy factors.
Autism spectrum disorder has long been thought to involve inherited genetic traits, and some previous research also suggest that some non-inherited traits and maternal characteristics may also play a role.
For the current study, researchers examined data on births from 1998 to 2007 in Denmark, Finland, Sweden, Israel, and Western Australia.
Overall, about 80 percent of the variation in risk for autism was linked to inherited genetic traits, although this ranged from 51 percent in Finland to almost 87 percent in Israel.
Sven Sandin, senior author of the study and a researcher at the Karolinska Institute in Stockholm, Sweden, said: "The results show that genetic factors are most important (about 80 percent of the variation in risk) but that the environment also play a role."
The study included more than 2 million children from more than 680,000 families who were monitored until they reached 16 years of age. Slightly more than 22,000 kids were diagnosed with autism.
So-called maternal effects, such as a preterm delivery or certain medical issues during pregnancy, did not appear to explain variation in autism risk, researchers report in JAMA Psychiatry.
Dr. Jeremy Veenstra-VanderWeele, co-author of an editorial accompanying the study and a psychiatrist at the Center for Autism and the Developing Brain at New York Hospital, said: "These results do not change what we do now in terms of autism prevention or treatment, but they do suggest that we should think about genetic testing, both using the technology that we have available now and using approaches that may improve over the next decade."
