BAKERSFIELD, Calif. -- The Centers for Disease Control and Prevention estimates that one out of every 166 children has autism spectrum disorder in the U.S. But scientists have remained divided on the exact causes of the disorder.

Now, three new studies have found that gene variants involved in forming connections between different parts of the brain put people at increased risk for developing the disorder.

All three studies were aimed at finding clues about the causes of this complex disorder by looking at the differences in DNA between people who have autism and people who do not.

The largest of the three studies included more than 10,000 subjects. Most of the gene variants identified contributed only a small risk on their own.

But taken together, the tiny mutations in a single chromosome may account for 15 percent of all autism cases.

Scientists said the genes may alter the pattern of brain cell connections in those with autism. They hoped the genetic clues will provide insight into how this mysterious disorder arises and how we might treat it in the future.