Bottom Line: Siblings born in a family after other children with autism spectrum disorder (ASD) or attention-deficit/hyperactivity disorder (ADHD) were more likely to be diagnosed with the same disorder or the other disorder.
Why The Research Is Interesting: ADHD and ASD are common neurodevelopmental disorders that likely share some genetic factors and biological influences. Estimating recurrence risk in families is a way to measure shared genetic factors. Such risk estimates are often based on the total number of siblings in a family rather than being limited to later-born siblings (those born after children with ASD or ADHD) so that risk can be underestimated if families decide to stop having children after a child develops ASD or ADHD. This study focused on risk for later-born siblings.
Who and What: A total of 15,175 later-born siblings classified by familial risk based on an older child's diagnosis: ADHD risk (730), ASD risk (158) and no known risk (14,287); data were extracted from two large health care system in the United States.
How (Study Design): This was a population-based study.
Authors: Meghan Miller, Ph.D., of the University of California Davis Health System, Sacramento, California, and coauthors
Study Limitations: These include a selective sample, lack of information on half- or full-sibling status, and data drawn from general medical records.
Related Material: The editorial, "Later Sibling Recurrence of Autism Spectrum Disorder and Attention-Deficit/Hyperactivity Disorder: Clinical and Mechanistic Insights," by Tony Charman, Ph.D., of King's College London, and Emily J.H. Jones, Ph.D., of the University of London, both in the United Kingdom, also is available on the For The Media website.
To Learn More: The full study is available on the For The Media website.
Editor's Note: The article contains funding/support disclosures. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.
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