“Indeed, when Sandin tracked autism diagnoses over time among the sibling pairs, he found that genetics likely accounts for around 83% of the disorder. That compares to nearly 90% reported in previous studies of twins only. Using the new model, environmental factors probably contribute around 17% to the risk of developing autism.
“This is why it is important to have different study designs,” says Sandin. “We have a family-based approach, and there are other approaches for twin studies and genetics studies. All of them seem to be converging on the same number of 80% to 90%.”