ADHD News & Research

New Study: Incidence of ASD Higher in Children with an Autistic Aunt or Uncle

A large NIH study of autism risk factors finds that 3 to 5 percent of children with an aunt or uncle on the autism spectrum also have ASD — at least twice the rate found in the general population. The research also suggests that autism genes pass equally from both maternal and paternal relatives.

May 22, 2020

A child whose aunt or uncle has autism spectrum disorder (ASD) is significantly more likely to have autism, according to a large study of more than 850,000 families in Sweden. The study, funded by that National Institutes of Health (NIH), is the first population-wide estimate of autism risk in children.

In studying the Swedish national registers of births and family relationships for children born between 2003 and 2012, researchers found that ASD was diagnosed in approximately 13,000 children, or 1.5 percent of the total. Among the population of children with an autistic aunt or uncle, this number jumped to 3 to 5 percent. This suggests that having an aunt or uncle with autism may increase a child’s likelihood of having ASD by 100 to 230%.

The research showed this autism link for children with both maternal and paternal relatives on the spectrum. Children of mothers with one or more siblings with ASD were roughly three times more likely to have the disorder than were children in the general population. Children of fathers with one or more siblings with ASD were twice as likely to have ASD as were children in the general population.

This finding debunks the theory that biological mothers are less likely to pass along genes associated with autism than are fathers. Researchers say their study results indicate that being female does not offer more tolerance of autism risk factors.

The findings were published in Biological Psychiatry.1 John N. Constantino, M.D., a professor of psychiatry and pediatrics at the Washington University School of Medicine in St. Louis, Missouri led the study along with colleagues in the United States and Sweden.

Autism is a complex developmental disorder characterized by social challenges, repetitive behaviors, and nonverbal communication. Rates of autism have tripled in the U.S. since the Centers for Disease Control and Prevent (CDC) started following the disorder in 2000; a recent report found that 1.85 percent of children in the U.S. — or 1 in 54 — has autism today, compared to .67 percent in 2000. 2

Scientist can’t pinpoint the exact causes of autism, but some studies have found the disorder more prevalent in males than females.3 Most physicians agree that ASD is a result of abnormalities in brain structure or function, and they are continuing to study a number of theories including hereditary risk, the impact of genetics, and other medical problems.

Sources

1Bai D, Marrus N, Hon Kei Yip B, Reichenberg A, Constantino J, Sandin S. (2020) Biological Psychiatry. Inherited risk for autism through maternal and paternal lineage. ddoi: https://doi.org/10.1016/j.biopsych.2020.03.013

2Centers for Disease Control and Prevention.Data and Statistics on Autism Spectrum Disorder. Last reviewed March 25, 2020. Accessed May 21, 2020.

3Werling DM, Geschwind DH. Sex differences in autism spectrum disorders. Curr Opin Neurol. 2013;26(2):146‐153. doi:10.1097/WCO.0b013e32835ee548.

Updated on May 22, 2020

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