One in 31 children in the U.S. is diagnosed with autism spectrum disorder by their 8th birthday, the Centers for Disease Control and Prevention reported Tuesday.

The finding, based on an analysis of medical records from 2022, reflects a dramatic rise in autism over the past two decades. Previous CDC reports showed that 1 in 54 8-year-olds had been diagnosed with autism in 2016. In 2000, it was 1 in 150.

“The most striking piece of this is how unbelievably common presentations of autism are,” said Zachary Warren, an author of the new report.

Warren, also the executive director of the Vanderbilt Kennedy Center’s Treatment and Research Institute for Autism Spectrum Disorders (TRIAD) in Nashville, largely attributed the increases to improvements in detecting the developmental brain disorder.

Doctors are better than ever at identifying autism, with awareness at an all-time high. “Without a doubt, we’ve become exceptionally efficient in this surveillance work,” Warren said.

What other factors could be causing the rise in autism?

Answers are both inconclusive and wildly complicated. Potential causes have been scrutinized for decades, and there doesn’t seem to be a single smoking gun. The leading theory lies in genetics.

“We have pretty compelling data that there are causes of autism, not a single cause,” Warren said. “We may have hundreds, if not 1000s, of different neurogenetic factors that influence presentations of autism.”

Despite proven research to the contrary, Health and Human Services Secretary Robert F. Kennedy, Jr has repeatedly suggested that vaccines — specifically the shots that protect against measles, mumps and rubella — are linked to autism.

That link has been widely debunked, but continues to contribute to a decline in vaccine uptake across the U.S. — even amid a growing measles outbreak that’s sickened hundreds and killed two small children in Texas.

The CDC study also looked at autism diagnoses among 4-year-olds, estimated to be 1 in 34 in 2022.

Boys were three times more likely than girls to be diagnosed with autism. Diagnoses were also more common among Black and Hispanic children compared with white children.

The disorder appears to be a focus of the Trump administration. Both the president and Health and Human Services Secretary Robert F. Kennedy Jr. have said it’s critical to find what’s causing autism in kids.

During a meeting at the White House last week, Kennedy said his agency will move forward with a “massive testing and research effort” to find the cause of autism by September.

It was unclear how the HHS effort would be different from previous research.