Previously, studies had estimated between 3 and 10 percent of siblings of autistic children would develop the disorder. The new research shows a higher number--just more than 18 percent. The study also found that boys are more likely than girls to develop autism--26 percent of boys with autistic siblings developed symptoms, compared to only 9 percent of girls, a nearly three-fold difference.
Autism has no known cause but experts believe that genetics and external influences are involved. Research is examining whether these could include infections, pollution and other non-inherited problems. [Lead researcher Sally] Ozonoff noted that siblings often are exposed to similar outside influences, which could partly explain the study results.
The study is an important addition to autism research and "has critical implications for families who are deciding whether they'll have another child," said Catherine Lord, director of the Institute for Brain Development at New York-Presbyterian/Weill Cornell Medical Center. Lord was not involved in the study.
Infants in the study were enrolled before they showed any signs of autism, such as poor eye contact and little social interaction.
Autism is the spectrum of developmental, cognitive, and behavioral disorders that affects an estimated 1.5 million Americans.
(image via Babble)