What's behind rising autism rates: A broader definition of autism and better screening

President-elect Donald Trump seemed to entertain the discredited theory that vaccines cause autism as he answered questions from journalists at a press conference Monday at his Mar-a-Lago club.

Trump said Robert F. Kennedy Jr., his choice to lead the Department of Health and Human Services who has been an anti-vaccine advocate, would look into the reasons for rising autism rates.

Trump, seeming to respond to Senate Republican leader Mitch McConnell's defense of the polio vaccine, called himself “a big believer in it.”

“You’re not going to lose the polio vaccine,” Trump said.

A look at autism rates and why they are rising:

What is autism?

Autism is a developmental disability caused by differences in the brain. There are many possible symptoms, many of which overlap with other diagnoses. They can include delays in language and learning, social and emotional withdrawal, and an unusual need for routine. Scientists believe genetics can play a role.

What is the rate of autism among U.S. children?

Among all U.S. 8-year-olds, 1 in 36 had autism in 2020. That's according to the most recent estimate from the Centers for Disease Control and Prevention. That’s up from 1 in 44 two years earlier.

Why is the rate of autism rising?

There are no blood or biological tests for autism. It’s identified by making judgments about a child’s behavior.

For decades, the diagnosis was given only to kids with severe problems communicating or socializing and those with unusual, repetitive behaviors. But around 30 years ago, the term became shorthand for a group of milder, related conditions known as ″autism spectrum disorders.”

“Most of the increase in recent decades is in relatively mildly affected children and adults, so maybe in the past we wouldn’t have called it autism,” explained Maureen Durkin, professor of population health sciences at the University of Wisconsin-Madison.

With improved screening and autism services, diagnosis is increasingly happening at younger ages. And there's been more awareness and advocacy for Black and Hispanic families too, leading to an increase in autism diagnosed among those groups.

Does autism have anything to do with vaccines?

No. Scientists have ruled out a link between vaccines and autism, a theory that stemmed from falsified information in a 1998 paper that was later retracted by the medical journal that published it.

Repeated scientific studies in the U.S. and abroad have found no evidence that vaccines in general or those with thimerosal cause autism. That preservative has been removed from routine childhood immunizations; while it remains in some flu vaccines, there are thimerosal-free versions.

The American Academy of Pediatrics calls vaccines “one of the most significant medical innovations of our time.”

What did Mitch McConnell say about vaccines?

McConnell, who had polio as a child, said any of Trump’s nominees seeking Senate confirmation should “steer clear” of efforts to discredit the polio vaccine.

“Efforts to undermine public confidence in proven cures are not just uninformed — they’re dangerous,” McConnell said in a statement Friday. “Anyone seeking the Senate’s consent to serve in the incoming Administration would do well to steer clear of even the appearance of association with such efforts.”