NPR Sponsor/Advertisement Voice (2:25)

Wow.

John Hamilton (2:25)

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.

Emily Kwong (2:32)

Today on the show. Amid all the misinformation, what does science have to say about autism and what.

John Hamilton (2:39)

Scientists still don't know?

Emily Kwong (2:40)

You are listening to Shortwave, the science podcast from npr.

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Emily Kwong (4:03)

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?

John Hamilton (4:12)

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, 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.

Emily Kwong (4:49)

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?

John Hamilton (5:03)

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 Brian 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 refrigerator mother theory of autism.

Emily Kwong (5:35)

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

John Hamilton (5:41)

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 two. 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.

Emily Kwong (6:07)

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

John Hamilton (6:14)

Yeah, there are definitely other factors that don't just run in families. And one of these is something called spontaneous mutations. These. 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.

Emily Kwong (6:41)

What about environmental risk? Because Robert F. Kennedy, Jr. The Secretary of health and human services, says toxins in the environment are causing an epidemic of autism, unquote. Is that misinform information?

John Hamilton (6:53)

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.

Emily Kwong (7:03)

Why is that?

John Hamilton (7:04)

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.

Emily Kwong (7:50)

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

John Hamilton (7:55)

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.

Emily Kwong (8:20)

Wow.

John Hamilton (8:20)

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.

Emily Kwong (8:42)

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?

John Hamilton (8:52)

So the most recent statistics from the Centers for Disease Control and Prevention, they now show that about 3.2% of 8 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 disorder.

Emily Kwong (9:37)

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. These rates?

John Hamilton (9:46)

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. We've even got an autistic Barbie doll.

Emily Kwong (10:17)

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

John Hamilton (10:21)

Oh, yeah. Part of the new fashionistas line for 2026. Accessorized. She's got a fidget spinner and those noise canceling headphones for, you know, sensory overload. Right. Mattel even released this video about the new doll.

Emily Kwong (10:35)

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, having a Barbie doll. 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?

John Hamilton (11:01)

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

Emily Kwong (11:06)

Okay.

John Hamilton (11:06)

But when scientists look at lots of brains, they've detected some subtle differ. 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 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.

Emily Kwong (11:43)

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

John Hamilton (11:50)

They're not super close. I mean, autism is still this huge mystery.

Emily Kwong (11:55)

Yeah.

John Hamilton (11:56)

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. 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 Paschka 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.

Dr. Sergio Paschka (12:31)

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.

John Hamilton (12:48)

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

Emily Kwong (12:56)

That's clever research.

John Hamilton (12:57)

Very clever research. And not easy.

Emily Kwong (12:59)

Yeah.

John Hamilton (13:00)

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

Emily Kwong (13:05)

I'm so curious. What did they find?

John Hamilton (13:07)

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

Dr. Sergio Paschka (13:22)

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? 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?

John Hamilton (13:40)

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.

Emily Kwong (14:03)

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 Shortwave.

John Hamilton (14:11)

Always a pleasure, Emily.

Emily Kwong (14:13)

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.

John Hamilton (14:39)

How could your favorite NPR podcast get any better? Well, what if it had bonus features such as extended interviews and zero sponsor breaks? There is a remarkably easy way to turn that fantasy into reality. It's called NPR. You get perks across more than 25 NPR podcasts while supporting the teams that make them make great podcasts even greater by visiting plus.NPR.org evergreen trees are Pacific.

Emily Kwong (15:05)

Northwest icons in journalism. An evergreen story isn't tied to one news cycle. It goes deep and helps you understand the world. The Evergreen is also a podcast from OPB about the Northwest. I'm Jen Chavez. Listen to the Evergreen podcast from OPB every Monday, part of the NPR Network.

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President Trump says he wants to make America skilled again, but tradeswomen worry that his crackdown on DEI will undo decades of progress.

John Hamilton (15:32)

You cannot look at the workforce of the construction trades and say they've taken DEI too far.

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This weekend on the Sunday Story, what role is there for women in the skilled trades renaissance? Listen now to the Sunday Story on the up first podcast from NPR.