Support for NPR and the following message come from the William and Flora Hewlett Foundation, investing in creative thinkers and problem solvers who help people, communities, and the planet flourish. More information is available at Hewlett.org. You're listening to Shortwave from NPR. Hey Shortwaveers, Emily Quank 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. 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? That is definitely misinformation because researchers have found autism in pretty much every group they've ever studied around the world and it may 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. 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. We did. We've linked the episode in our show notes. Let's revisit though. Is there any science behind that claim about Tylenol? 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 use during pregnancy. And once again, it found no link to autism. Good to know. And coming from that same press conference, there was still more misinformation. What else was said, John? Well, FDA commissioner Marty McCarrie 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 Luke of Warren, this vitamin B9, can reduce their symptoms. So pediatricians and neurologists are opposed to the administration's plan to make Luke of Warren widely available to children on the spectrum. And I really wanted to come on shortwave to kind of set the record straight on all of this, all this misinformation about autism. To down the show, amid all the misinformation, what does science have to say about autism? And what scientists still don't know? You are listening to shortwave, the science podcast from NPR. This message comes from Wise, the app for international people using money around the globe. You can send, spend, and receive an up to 40 currencies with only a few simple tabs. Be smart, get Wise. Download the Wise app today or visit Wise.com, T's and C's apply. Support for NPR and the following message come from the William and Flora Hulett Foundation, investing in creative thinkers and problem solvers who help people, communities, and the planet flourish. More information is available at huelet.org. 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? No, at least not yet. So autism spectrum disorders still baggnaused 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 bogus 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. Yeah, the spectrum is broad and it also encompasses millions of Americans. Yes. 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? 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 Conner, who wrote the first paper describing autism. Another one was Bruno Betelheim, 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. Betelheim even popularized what became known as the quote refrigerator mother theory of autism. So these scientists back in the day falsely hypothesized that it was the mother's fault. Her child at autism. 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 an autistic, there was a decent chance the other one would be two. And when the twins were identical, so they had exactly the same genes, that risk was even higher, 60 to 90 percent depending on the study. Wow. Is autism determined just by genes, though? Is there any other factor that leads to it? Yeah, there 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. 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? It's certainly misleading. There is pretty good evidence that exposure to some heavy metals, like lead mercury during pregnancy, can increase the risk of having a child with autism. Why is that? 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 the form of mercury, but there's no evidence that this poses a risk. Why is Kennedy so fixated on vaccines when science points to the contrary? 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 there's not much evidence that any of those factors is having a big impact on the rate of autism in our country. 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. To study that, you need to know precisely which exposures occurred several years before a child is going to be diagnosed with autism. Is there, as Kennedy says, an epidemic of autism? The rates of autism diagnosis have been going up for years, so what is driving that? The most recent statistics from the Centers for Disease Control and Prevention. They now show that about 3.2 percent 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. Autism was still considered a form of childhood schizophrenia until the 1980s. It wasn't until 2013 that the current autism spectrum disorder diagnosis came along and wrapped in conditions that used to be separate, like aspergers and pervasive developmental disorders. 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. Exactly. 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. I saw her. She's so cute. She has noise canceling headphones. Oh yeah, part of the new Fashionista's line for 2026. Successorized. She got a fidget spinner and those noise canceling headphones for sensory overload. Yeah, yeah, yeah. Mattel even released this video about the new doll. I've wanted there to be an autistic doll. Since I knew I had autism, it means a lot to finally see this happen. Having a Barbie doll. This is so cool. I mean, 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 neuro-typical brains? Yes and no. You can't look at a brain and say for sure that, oh, this comes from a person who is autistic. Okay. 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 than it slows down. And the connections between brain cells tend to have a different pattern. So, for example, studies have found that autism 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. That makes sense. And how close are scientists to understanding how genetic strives those differences in brainwiring? They're not super close. Autism is still this huge mystery. 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. Sergio 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 internorons. Internorons 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 away. The cells may not move appropriately or they may stop or maybe they're not even born. So to find out what was going on, Sergio's team used gene editing to create these organoids that had some of the specific changes associated with autism. That's clever research. Very clever research. And not easy. Yeah. So then they watched to see how each of these changes would affect these internorons. I'm so curious. What did they find? They found that about 10% of the genetic changes either prevented these internorons 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. 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. Wow. Are we going to be able to cluster, to classify some subtype sov autism based on the biological process that they're disrupting in the brain? 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 and 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. 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, Jorge. Always a pleasure Emily. 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 Shortwave from NPR. See you tomorrow. Support for NPR and the following message come from the William and Flora Hulett Foundation, investing in creative thinkers and problem solvers who help people, communities, and the planet flourish. More information is available at Hulett.org.
