Autism: debunking Trump claims, and what scientists still don't know

Autism has a long history of misinformation that continues to today. The Trump administration has perpetuated some of this misinformation in the last year. Among other things, officials have claimed certain groups of people don’t get the condition and that taking Tylenol while pregnant causes autism to later develop in children. Today, NPR Science Correspondent Jon Hamilton https://www.npr.org/people/2100615/jon-hamilton sets the record straight with host Emily Kwong https://www.npr.org/people/767284140/emily-kwong on what scientists do and don’t know about autism. If you liked this episode, check out our episodes on an Autism researcher’s take on Trump’s claims about Tylenol https://www.npr.org/2025/09/24/nx-s1-5522134/autism-tylenol-trump-research-pain-pregnacy and a Fragile X treatment https://www.npr.org/2021/05/05/993838102/a-fragile-x-treatment-may-be-on-the-horizon that may be on the horizon. Interested in more science in the news? Email us your question at [email protected] mailto:[email protected]. Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave http://plus.npr.org/shortwave. This episode was produced by Berly McCoy. It was edited by Rebecca Ramirez. Tyler Jones checked the facts. The audio engineer was Damian Herring. See pcm.adswizz.com https://pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences. NPR Privacy Policy https://www.npr.org/about-npr/179878450/privacy-policy

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Speaker 00

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• 0:18Emily Kwong?

  You're listening to Short Wave from NPR. Hey, Short Wavers. Emily Kwong here. You may know that the Trump administration has put forward a lot of misinformation about autism. Here's the president himself at a press conference in 2025.

• 0:34Speaker 02

  There are certain groups of people that don't take vaccines and don't take any pills that have no autism, that have no autism. Does that tell you something?

• 0:45Emily Kwong?

  That is definitely misinformation because researchers have found autism in pretty much every group they've ever studied around the world. And it made no difference whether or not they'd been vaccinated. I'm here with John Hamilton, our resident brain correspondent. And you've been tracking the spread of this misinformation for months.

• 1:03Speaker 03

  Hey, Emily. Yes, I have, including some other claims made at that conference, like when federal health officials also told pregnant women not to take Tylenol because it might cause their children to develop autism, which I know you guys did a whole episode, True Squatting.

• 1:17Emily Kwong?

  We did. We've linked the episode in our show notes. Let's revisit, though. Is there any science behind that claim about Tylenol?

• 1:25Speaker 03

  Not much. In 2024, there was a very large study in Sweden that found no link. In 2025, there was an analysis of data from a bunch of smaller studies that found a possible link. But that analysis didn't account for factors like infection or fever, which can, on their own, increase the risk of autism. And earlier this year, there was a larger and more rigorous review of Tylenol used during pregnancy. And once again, it found no link to autism.

• 1:52Emily Kwong?

  Good to know. And coming from that same press conference, there was still more misinformation. What else was said, John?

• 1:59Speaker 03

  Well, FDA Commissioner Marty Makary said they were going to formalize vitamin B9 as a treatment for children with autism. That's on the assumption that autistic kids have a B9 deficiency, but it's still not clear how many autistic kids actually have this deficiency, let alone whether leucovorin, this vitamin B9, can reduce their symptoms.

• 2:19Emily Kwong?

  Huh.

• 2:20Speaker 03

  So pediatricians and neurologists are opposed to the administration's plan to make leucovorin widely available to children on the spectrum.

• 2:27Emily Kwong?

  Wow.

• 2:27Speaker 03

  And I really wanted to come on Short Wave to kind of set the record straight on all of this, you know, all this misinformation about autism.

• 2:34Emily Kwong?

  Today on the show, amid all the misinformation, what does science have to say about autism?

• 2:40Speaker 03

  And what scientists still don't know.

• 2:42Emily Kwong?

  You are listening to Short Wave, the science podcast from NPR.

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• 4:11Emily Kwong?

  Okay, John, there is a lot to talk about. Could you just start by defining what autism is? I mean, is it something that you can even detect by looking at a person's brain?

• 4:20Speaker 03

  No, at least not yet. So autism spectrum disorder is still diagnosed by the presence of certain behaviors. For example, people have difficulty recognizing social cues, or they avoid eye contact. Think in literal terms, that want strict routines, have intense but narrowly focused interests, right? There's all that. Beyond that, you have some autistic people who stim. They may flap their hands or make other repetitive movements. Some are also very sensitive to light or sound or touch. But, you know, every autistic person has their own unique constellation of these behaviors and characteristics.

• 4:57Emily Kwong?

  Yeah, the spectrum is broad, and it also encompasses millions of Americans.

• 5:02Speaker 03

  Yes.

• 5:02Emily Kwong?

  Like, millions of adults, millions of kids have autism spectrum disorder. So how do we get to this place where federal health officials are saying things about autism that just are not true?

• 5:12Speaker 03

  There is a long history of misinformation about autism, and sadly, it includes some scientists who got it really wrong back in the 1940s. One of them was a guy named Dr. Leo Connor, who wrote the first paper describing autism. Another one was Bruno Bettelheim, a famous psychologist who studied children with autism. And both of these men thought autism was caused by parents who weren't warm and affectionate with their young children. Bettelheim even popularized what became known as the, quote, "refrigerator mother" theory of autism.

• 5:44Emily Kwong?

  So these scientists back in the day falsely hypothesized that it was the mother's fault. Her child had autism?

• 5:50Speaker 03

  Yep. And to this day, many people in the autism community are understandably bitter about that theory, which persisted until at least the 1970s. That's when scientists began studying autism in twins. They realized that if one twin was autistic, there was a decent chance the other one would be too. And when the twins were identical, so they had exactly the same genes, that risk was even higher, 60 to 90%, depending on the study.

• 6:15Emily Kwong?

  Wow. Is autism determined just by genes, though? Is there any other factor that leads to it?

• 6:22Speaker 03

  Yeah, there are definitely other factors that don't just run in families. And one of these is something called spontaneous mutations. These are genetic differences that aren't inherited. They occur spontaneously in sperm, especially from older fathers. They can also occur in an egg or even a developing embryo. And studies show that in low-risk families, that's families where only a single child has autism, spontaneous mutations are involved more than half the time.

• 6:49Emily Kwong?

  What about environmental risk? Because Robert F. Kennedy Jr., the Secretary of Health and Human Services, says toxins in the environment are causing an, quote, epidemic of autism, unquote. Is that misinformation?

• 7:02Speaker 03

  It's certainly misleading. There is pretty good evidence that exposure to some heavy metals, like lead and mercury, during pregnancy can increase the risk of having a child with autism.

• 7:11Emily Kwong?

  Why is that?

• 7:13Speaker 03

  Because these heavy metals can affect early brain development, and that's when autism begins. But exposure to these metals is way less than it used to be. Lead has been removed from gasoline and paint, and power plants now put less mercury in the air. Besides, Kennedy's list of toxins doesn't focus on those environmental risks. Instead, it includes items like childhood vaccines, vaccines which have been studied extensively and are clearly not a risk factor for autism. Also, these vaccines don't contain any heavy metals anymore. They used to be preserved with tiny amounts of mercury, but that ended about 25 years ago. It is true that multi-dose flu shots are still preserved with a form of mercury, but there's no evidence that this poses a risk.

• 7:58Emily Kwong?

  Why is Kennedy so fixated on vaccines when science points to the contrary?

• 8:04Speaker 03

  This goes way back in his legal history. He's always been very interested in the potential harm caused by things like pesticides and chemicals in the environment. He's also always been a little suspicious of medicines, including Tylenol. But, you know, there's not much evidence that any of those factors is having a big impact on the rate of autism in our country.

• 8:28Emily Kwong?

  Wow.

• 8:28Speaker 03

  To be fair, environmental factors like that can be really hard to study. One reason is that these brain changes associated with autism appear to start as early as the second trimester of pregnancy. So to study that, you need to know precisely which exposures occurred several years before a child is going to be diagnosed with autism.

• 8:50Emily Kwong?

  So is there, as Kennedy says, quote, "an epidemic of autism," end quote? Because the rates of autism diagnosis have been going up for years. So what is driving that?

• 9:00Speaker 03

  So the most recent statistics from the Centers for Disease Control and Prevention, they now show that about 3.2% of eight-year-old children have autism spectrum disorder. That's about twice the percentage that was reported back in 2010. So more kids are being diagnosed, for sure. But most scientists agree that a big part of that increase has to do with factors like increased awareness, more screening, a much broader definition of autism. I mean, autism was still considered a form of childhood schizophrenia until the 1980s. And it wasn't until 2013 that the current autism spectrum disorder diagnosis came along and wrapped in conditions that used to be separate, like Asperger's and pervasive developmental

• 9:45Speaker 03

  disorders.

• 9:46Emily Kwong?

  So you're saying it's not that there's more autism, it's that we're seeing more autism diagnoses that could be driving up these rates?

• 9:54Speaker 03

  Exactly. And for instance, you have a lot more girls who are being diagnosed with autism. That's because healthcare professionals now recognize that girls on the spectrum may have different symptoms than boys. Another factor is that parents and teachers have come to realize that an autism diagnosis can actually help a child because it makes them eligible for therapies and special education programs. And then there's stigma. It's just less of a problem these days. Lots of kids are not shy anymore about being autistic. You know, we've even got an autistic Barbie doll.

• 10:25Emily Kwong?

  I saw her. She's so cute. She has noise-canceling headphones.

• 10:29Speaker 03

  Oh, yeah. Part of the new Fashionista's line for 2026. Accessorized, she's got a fidget spinner and those noise-canceling headphones.

• 10:37Emily Kwong?

  Nice.

• 10:37Speaker 03

  For, you know, sensory overload, right?

• 10:39Emily Kwong?

  Yeah, yeah, yeah.

• 10:40Speaker 03

  Mattel even released this video about the new doll.

• 10:44Speaker 05

  I've wanted there to be an autistic doll, like, since I knew I had autism. It means a lot to finally see this happen.

• 10:50Speaker 06

  Having a Barbie doll.

• 10:51Emily Kwong?

  This is so cool. I mean, and not only is there more social support for conversations about neurodiversity and autism, there's also just been so much more research. Do scientists know what it even means to be autistic, like biologically, how autistic brains are different than neurotypical brains?

• 11:09Speaker 03

  Yes and no. You can't look at a brain and say for sure that, oh, this comes from a person who is autistic.

• 11:14Emily Kwong?

  Okay.

• 11:15Speaker 03

  But when scientists look at lots of brains, they've detected some subtle differences. In autism, brain growth has a different pattern. It often appears to get accelerated during the first few years of life, then it slows down. And the connections between brain cells tend to have a different pattern. So for example, studies have found that autism is associated with more connections within specific areas of the brain, but fewer connections between these brain areas. And that's interesting because it could explain why autism can sometimes make it harder for a person to integrate information from lots of different sources.

• 11:51Emily Kwong?

  That makes sense. And how close are scientists to understanding how genetics drives those differences in brain wiring?

• 11:59Speaker 03

  They're not super close. Autism is still this huge mystery.

• 12:04Emily Kwong?

  Yeah.

• 12:04Speaker 03

  And especially because it looks like there are hundreds of genes that are involved. So really complicated. But there are some really intriguing findings coming out from scientists who study these things called brain organoids. Now, these are these clusters of human brain cells that can live for months or years in the lab. And in many ways, they develop like the brain of a fetus. I spoke with Dr. Surjip Pashka of Stanford University. He does a lot of research with brain organoids. And he's been studying how genes associated with autism would affect brain cells called interneurons.

• 12:40Speaker 07

  Interneurons are born in deep regions of the brain, and then they have to migrate all the way to the cortex. So now you can imagine that during that migration, a lot of things could go awry. The cells may not move appropriately, or they may stop, or maybe they're not even born.

• 12:56Speaker 03

  So to find out what was going on, Surj's team used gene editing to create these organoids that had some of the specific changes associated with autism.

• 13:05Emily Kwong?

  That's clever research.

• 13:06Speaker 03

  Very clever research.

• 13:07Emily Kwong?

  Interesting.

• 13:07Speaker 03

  And not easy.

• 13:08Emily Kwong?

  Yeah.

• 13:09Speaker 03

  So then they watched to see how each of these changes would affect these interneurons.

• 13:14Emily Kwong?

  I'm so curious, what did They find.

• 13:16Speaker 03

  They found that about 10% of the genetic changes either prevented these inner neurons from being born or impaired their ability to migrate to the right place in the brain. And Sergio told me that experiment he did is really just the beginning.

• 13:30Speaker 07

  With hundreds of genes now associated with autism, a fundamental question is, how many forms of autism are we going to really have, biologically speaking?

• 13:39Emily Kwong?

  Wow.

• 13:39Speaker 07

  Are we going to be able to cluster, to classify some subtypes of autism based on the biological process that they're disrupting in the brain?

• 13:49Speaker 03

  That is a huge question, because if scientists can link genetic changes, genetic variations, to differences in brain development, they could explain why autism looks so different in different people. And it could also help identify treatments that target a specific system in the brain, instead of just trying to treat autism spectrum disorder as one whole thing.

• 14:12Emily Kwong?

  John, you have rocked my world. I did not know any of this science. And knowing what's misinformation is really good, too. Thank you so much for coming on Short Wave.

• 14:20Speaker 03

  Always a pleasure, Emily.

• 14:22Emily Kwong?

  If you liked this episode, follow us on the NPR app or wherever else you get your podcasts. Also, check out our episodes on Tylenol and autism and on Fragile X Syndrome, which was reported by John Hamilton. I'm Emily Kwong. Thank you for listening to Short Wave from NPR. See you tomorrow.

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