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Child's Risk When Older Sibling Has Autism

About 7 times higher odds seen for full-siblings in large Danish study, lower than other research


The new study results will be valuable to families who have a child already diagnosed with autism, said Dr. Jefry Biehler, chair of pediatrics at Miami Children's Hospital, who was not involved in the study. "Because early intervention and diagnosis are important to the well-being of children, this information can be very important to families who have a child with known autism spectrum disorder," he said.

The overall increased risk found of 7 percent "should be relatively reassuring to families who already have one child with an autism spectrum disorder," said Dr. Andrew Adesman, chief of developmental and behavioral pediatrics at the Steven & Alexandra Cohen Children's Medical Center of New York. However, he added, "there is a possibility that this is an underestimate -- especially for families who have a more severely affected child."

For his part, Biehler said the findings continue to support the idea that the causes of autism arise from many factors. "Their conclusions support the view that both genetic and environmental factors may contribute to the risk of younger children developing these disorders when their older brother or sister are known to have ASD," he said.

To study author Gronborg, the findings suggest that "nongenetic and environmental factors may play far greater roles than previously thought."

The higher risk seen for siblings born to the same mother compared to the fathers may indicate that obstetrical factors may be playing important roles in causing the disorder, both Biehler and Adesman said.

Parents who have a child with autism should discuss the findings with their health care provider, Biehler said.

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