A child is highly likely to be autistic if an older sibling suffers from the disorder, says a new U.S. study.
Autism is a disorder of neural development, which affects the child’s ability to think and communicate and is generally known to show up in children within the age of three.
A research based on 664 children, who had at least one older brother or sister with autism, shows that about 19 percent of them were diagnosed with autism.
Among boys, 26 percent were detected with some form of autism, while the rate for girls was 9 percent.
This rate was higher than what the studies reported previously, which was about 3 to 14 percent.
If a child has more than one sibling with autism, the average risk of the youngest one to get diagnosed with the disorder shoots up to 32 percent.
"I have seen families with five kids with autism," said Dr. Fred Volkmar, a child psychiatrist and autism expert at Yale University.
Sally Ozonoff, a psychiatry and behavioral sciences professor with the Mind Institute at the University of California at Davis, said that parents of autistic children often ask her, "How likely am I to have another child" with autism?
The cause for autism is not known, but the experts believe genetic and external influences are involved.
"Genes is a large part of autism, but it's not the whole story. Non-genetic factors are also important, but we don't know exactly what they are." Ozonoff says.
She says that siblings are often exposed to the same environment and influences, which could probably explain the connection.