Study: Autistic Sibling’s Gender Affects Younger Sibling’s Autism Risk

For a while know, it’s been well-known that having a sibling with autism increases one’s own autism risk. But the question is, does your sex or your sibling’s sex have anything to do with it? Does risk increase or decrease with certain genders?

Researchers at Harvard Medical School sought to find an answer to this question, and they published their results in JAMA Psychiatry. In short, the finding of the largest study ever to be conducted on this subject: yes, gender does play a role in sibling autism risk.

Adobe Stock/Christin Lola
Adobe Stock/Christin Lola

To reach their fascinating conclusions, researchers examined the 2008 to 2016 health insurance records of over 1.5 million, two-child families whose kids were between ages four and 18.

Through this data, they discovered that boys with older sisters on the spectrum had the highest risk of also having autism.

“For a girl to emerge with [autism] in the first place indicates that that is a high-risk family,” explained Nathan Palmer, one of the study’s authors.

When flipped the other way around, the results were opposite; girls with older brothers on the spectrum had the lowest risk of having autism.

Adobe Stock/Marzanna Syncerz
Adobe Stock/Marzanna Syncerz

The study also reinforces what researchers have already known for a while, that boys tend to have a higher chance of being autistic than girls do, and that more gene mutations are required in order for girls to get the disorder. (However, recent research has also indicated that the autism gender gap may not be as wide as we originally thought it was, due to the fact that some girls may have been overlooked).

While the results of this study are informative, they shouldn’t be taken dogmatically.

“Even for the group at highest risk—males with an older female sibling with autism—the odds are still about five to one that the child will be unaffected,” said Palmer. “What we have provided here is context for families who already have children with autism or another similar disorder and need a clearer perspective on recurrence risk.”

To learn what it’s like to have a sibling with autism, check out the touching video on the next page!


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