Children with Autistic Siblings have Higher Autism Risk

Children with an autistic sibling are at a seven times higher risk of being diagnosed with the behavioral disability, a new study has found. It also found that the risk of autism was higher even in children whose half-siblings were diagnosed with the condition, especially if they had the same mother, Reuters Health reported.

According to estimates by the Centers for Disease Control and Prevention (CDC), In the U.S., 1 in 88 children and 1 in every 54 boys are born with autism. Autism Spectrum Disorders (ASD) is a group of developmental disabilities that can cause significant social, communication and behavioral challenges. Research has shown that both genes and environment raise autism risk.

"I think a lot of autism researchers agree that the causes of autism are many and it's very complex," Therese Gronborg, who led the study at Aarhus University, told Reuters Health. "If it was only genetics we would see a much higher recurrence rate" among siblings."

The study was based on data of about 1.5 million children born in Denmark between 1980 and 2004. By the end of 2010, about 13,000 children had received an autism diagnosis. In this group, about 276 children, who had autistic siblings, were diagnosed with autism.

Analysis of the data showed that a child's risk of autism, if there was already an autistic child in the family, was between 4.5 and 10.5 percent, with an average of 7 percent.

In half siblings, the risk was higher if they had same mother- 2.4 times when compared with those who were related by their fathers (1.5 times).

There are many reasons for higher risk of autism diagnosis among siblings such as genes, maternal behavior and even parents' ability to detect signs of autism in their second child if they already have an autistic child.

The study is published in the journal JAMA Pediatrics.