DANVILLE, Pa. - Increased risk for autism appears to be linked to the Y chromosome, a Geisinger study found, offering a new explanation for the greater prevalence of autism in males. The results were published today in Nature Communications.

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by impaired social interaction and communication, and restricted and repetitive patterns of behavior, interests and activities. ASD is nearly four times more prevalent among males than females, but the reason for this disparity is not well understood.

One common hypothesis involves the difference in sex chromosomes between males and females-typical females have two X chromosomes, while typical males have one X and one Y chromosome.

"A leading theory in the field is that protective factors of the X chromosome lower autism risk in females," said Matthew Oetjens, Ph.D., assistant professor at Geisinger's Autism & Developmental Medicine Institute.

The Geisinger research team, led by Dr. Oetjens and Alexander Berry, Ph.D., staff scientist, sought to determine the effects of the X and Y chromosomes on autism risk by examining ASD diagnoses in people with an abnormal number of X or Y chromosomes, a genetic condition known as sex chromosome aneuploidy.

The team analyzed genetic and ASD diagnosis data on 177,416 patients enrolled in the Simons Foundation Powering Autism Research (SPARK) study and Geisinger's MyCode Community Health Initiative. They found that individuals with an additional X chromosome had no change in ASD risk, but that those with an additional Y chromosome were twice as likely to have an ASD diagnosis. This suggests a risk factor associated with the Y chromosome instead of a protective factor associated with the X chromosome.

"While these may seem like two sides of the same coin, our results encourage us to look for autism risk factors on the Y chromosome instead of limiting our search to protective factors on the X chromosome," Dr. Berry said. "However, further research is needed to identify the specific risk factor associated with the Y chromosome."

This analysis also confirms prior work by showing that the loss of an X or Y chromosome, known as Turner syndrome, is associated with a large increase in ASD risk. Further research is needed to determine whether the ASD risk factors associated with sex chromosome aneuploidy explains the sex difference in ASD prevalence.

About Geisinger College of Health Sciences
Geisinger College of Health Sciences is the research and education arm of the Geisinger family. Geisinger is committed to making better health easier for the more than 1 million people it serves. Geisinger is the inaugural member of Risant Health, a nonprofit dedicated to expanding and accelerating the adoption of value-based care. Founded more than 100 years ago by Abigail Geisinger, the system now includes 10 hospital campuses, a health plan with more than half a million members, and the College. The College houses a Research Institute, graduate medical education, and schools of medicine, nursing and graduate education, in addition to faculty and professional development programs. The College is committed to non-discrimination in all employment and educational opportunities. Visit geisinger.edu/gchs.