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Study Looks Beyond the Risk of Autism in Baby Siblings

February 14, 2013

Many younger sibs of children with autism have symptoms and delays that fall short of ASD but warrant early intervention

Autism tends to run in families. In 2011, Autism Speaks Baby Siblings Research Consortium (BSRC) found that autism affects one in five children born into families with a child already on the autism spectrum. But what about the younger siblings who don’t develop autism? In a new study, BSRC researchers report that, at age 3, more than one in five have developmental delays or autism symptoms. The findings appear today in the Journal of the American Academy of Child and Adolescent Psychiatry.

“What we found is that autism is not always all or nothing,” says lead researcher Daniel Messinger, Ph.D., professor of psychology and pediatrics at the University of Miami. “We are seeing a group of younger siblings who don’t have autism, but who would benefit from early intervention services.”

In their study, the researchers compared two groups of 3-year-olds without ASD – those who had an older sibling on the autism spectrum and those who did not. Of the 447 who had an affected older sibling, 21 percent had developmental delays or scored relatively high on a scale of autism symptoms. (Their symptoms still fell short of diagnosed ASD.) By comparison, this was true of just 7 percent of the children born into families not affected by autism.

Another 14 percent of the 3-year-olds with an affected older sibling scored relatively high on the scale of autism symptoms, but otherwise showed normal development. Surprisingly, 11 percent of the toddlers from unaffected families likewise fell into this group.

Importantly, nearly 65 percent of the younger siblings of affected children had no significant developmental delays or autism symptoms. This was true of 83 percent of the 3-year-olds from unaffected families.

“Our findings are not so much about percentages as they are about helping pediatricians and parents recognize the range of outcomes possible among the younger brothers and sisters of children with autism,” Dr. Messinger explains. “Two years ago, we determined that one in five will develop autism. Now we know that another group will have some developmental delays that can likewise benefit from early intervention services.”

“For good reason, parents who have a child with autism are concerned about the development of younger siblings,” comments Alycia Halladay, Ph.D., Autism Speaks senior director for environmental research. “A better understanding of the developmental issues that face these younger siblings will help parents and encourage healthcare providers to closely monitor development to promote earlier detection and intervention.” (See “Learn the Signs.”)

Autism Speaks helped support the new study by funding the creation of a BSRC database and the analysis of its information. The database enables more than 20 BSRC research groups to coordinate and share research findings. The consortium is a partnership between Autism Speaks and the National Institutes of Health, led by the National Institute of Child Health & Human Development. The consortium’s research furthers understanding of how autism develops, with a special focus on earlier diagnosis and treatment.

For a personal perspective on the new findings, please see this related blog post by Dr. Messinger and one of his co-authors, developmental psychologist Gregory Young, Ph.D., of the MIND Institute, at the University of California, Davis.

Autism Speaks began funding baby sibling research in 1997 and worked with the NICHD to form the Baby Siblings Research Consortium in 2003.  You can explore other BSRC projects funded by Autism Speaks here.