Most of the variation in risk for autism is explained by genetics rather than differences in environmental factors, like lifestyle or community characteristics or certain pregnancy outcomes, a study in five countries suggests.

Autism spectrum disorder has long been thought to involve inherited genetic traits, and previous research also suggests that some non-inherited traits and maternal characteristics may also play a role.

For this latest study, the researchers examined data on births from 1998 to 2007 in Denmark, Finland, Sweden, Israel and WA.

Overall, about 80% of the variation in risk for autism was linked to inherited genetic traits, although this ranged from 51% in Finland to almost 87% in Israel.