Have a Stutter? It Could Be Inherited

Summary

Podcast Summary: Short Wave – "Have a Stutter? It Could Be Inherited"

Date: September 3, 2025
Host: Emily Kwong (NPR)
Guests: Dylan Pruitt (Genetics researcher, FSU), Piper Belo (Geneticist, Vanderbilt University)

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Episode Overview

In this episode of Short Wave, host Emily Kwong interviews researchers Dylan Pruitt and Piper Belo about a landmark study uncovering genetic factors linked to stuttering. The episode explores how stuttering can run in families, the discovery of specific genetic regions associated with the condition, and what these findings mean for understanding, treating, and appreciating stuttering as a form of neurodiversity.

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Main Discussion Points and Insights

1. Personal Connection and Motivation

• Dylan Pruitt began stuttering at age 3 and participated in speech therapy as a child.
• Even through college, Pruitt found little robust science on stuttering's underlying causes, sparking his pursuit of research into the genetic aspects.
  • Quote (Dylan): “It was another way, kind of inspiring realizing that I could take action and pursue this field of study and really contribute to the field.” [01:37]

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2. The Big Research Question

• Stuttering often clusters in families, suggesting genetic links, but past explanations also blamed shared environment.
• The study aimed to determine whether the familial clustering was indeed genetic.
  • Quote (Piper Belo): “If you are a person who stutters, you have a much higher likelihood of having a second or third individual in your family who also stutters than you would expect by chance.” [03:53]

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3. Breakthrough Dataset via 23andMe

• Traditional stuttering research had low participant numbers (1,500-2,000); a much larger dataset was needed.
• Belo’s team gained access to the biobank from 23andMe, which included stuttering-related survey questions and genetic data from over 1 million users.
  • Quote (Emily): “You really got the... granddaddy of biobanks when it comes to stuttering research.” [06:13]
  • Quote (Piper Belo): “This direct to consumer genetic testing company 23andMe had a question on their survey that was, you know, do you ever have, you know, have you ever had a stutter or a stammer?” [06:00]

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4. Genome-Wide Association Study (GWAS) Explained

• GWAS approach: Identify areas of the genome that vary and correlate with whether individuals stutter.
  • Quote (Dylan): “When we look at everybody that has this trait and everybody that does not have this trait, what are the handful of variants that are associated?” [06:46]
  • Quote (Piper): “There's a large number of variants from all across the genome… some might increase your risk a little bit, others might decrease your risk a little bit.” [07:19]

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5. Key Findings: 57 Genetic Regions Linked to Stuttering

• 57 regions of the genome found to contribute to stuttering risk—often small effects, working in concert.
• The most notable gene: VRK2, which is also linked to rhythm ability and musicality.
  • Quote (Piper): “The number one gene that emerged from our study was this gene, VRK2... just come out a few months prior as the Number one hit in a very large analysis of rhythm ability, people's ability to clap to a beat. And so this was the first time anybody actually had found a shared genetic underpinning underlying both developmental stuttering and this sort of rhythmicity, rhythm and musicality phenotype or trait.” [08:24]
  • Quote (Dylan): “Knowing that speech and language is so intricately tied and knowing that essentially the primary deficit in stuttering is really the timing of speech, it really blew me away.” [09:20]

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6. Broader Associations and Clinical Implications

• Positive genetic correlations found between stuttering, depression, and autism.
• Negative genetic correlations with beat synchronization.
  • Quote (Dylan): “We observed positive correlation in males and females with depression. We also found correlations with autism and negative correlations with the beat synchronization.” [11:01]

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7. Subtypes and Sex Differences

• At stuttering onset (age 3), rates are similar between boys and girls.
• 80% of children who stutter recover; most who do are girls, resulting in persistent stuttering being more prevalent in boys.
• The reasons behind this sex difference remain unclear.
  • Quote (Piper): “When kids turn about three, the onset of stuttering is approximately equal between girls and boys…most of those that recover are girls. And if you don't recover as a child, you are very likely to stutter for life.” [11:40]

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8. Reframing Stuttering: Not About Finding a Cure

• The research aims not to “cure” stuttering, but to demystify and better understand it, seeing it as a form of neurodiversity.
• Hopes for more personalized support strategies tailored to individuals’ unique neurobiology rather than a one-size-fits-all model.
  • Quote (Dylan): “I think that stuttering is a beautiful and, in my view, underappreciated example of neurodiversity... our work helps us understand the genetic script behind that diversity.” [13:44]
  • Quote (Piper): “I don't think of this as a discovery that is sort of closing the door on a chapter in stuttering. I feel like we just threw every door and window open.” [14:37]

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Memorable Quotes & Moments

• Dylan Pruitt:

  • “I think this gives us a really unique direction to explore.” [09:20]
  • "I view our work as really about demystifying it." [13:44]

• Piper Belo:

  • "This was the first time anybody actually had found a shared genetic underpinning underlying both developmental stuttering and this sort of rhythmicity, rhythm and musicality phenotype." [08:24]
  • “We just threw every door and window open. Right. This is us approaching a starting line, not a finish line.” [14:37]

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Timestamps for Key Segments

• 00:39-01:30 — Dylan’s personal experience with stuttering
• 03:48-05:51 — The search for genetic connections & securing the 23andMe dataset
• 06:46-08:14 — GWAS explained and discovery of risk loci
• 08:24-09:20 — VRK2 gene discovery and link to rhythm
• 11:01-11:35 — Genetic associations with depression, autism, and beat synchronization
• 11:40-12:28 — Subtypes and sex differences in stuttering
• 13:44-14:37 — The importance of demystifying stuttering and pushing for individualized support

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Tone and Style

The episode is light, inquisitive, and enthusiastic—celebrating scientific breakthroughs while highlighting neurodiversity. The conversation remains accessible, sometimes playful, and consistently respectful of people who stutter.

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Conclusion

This Short Wave episode reveals groundbreaking genetic insights into stuttering, challenges outdated notions of its origins, and points toward a future where people who stutter receive understanding and personalized support instead of attempts to “fix” them. The work of Dylan Pruitt and Piper Belo highlights genetic connections to rhythm and language, reframing stuttering as a meaningful form of human diversity rather than a problem to eliminate.

Transcript

[NPR Sponsor Announcer]

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[Emily Kwong]

You're listening to Shortwave from npr. Hey, shortwavers. Emily Kwong here. And today we're going to meet Dylan Pruitt, a genetics researcher at Florida State University in the School of Communication Sciences and Disorders. And the particular condition Dylan studies, it's been with him most of his life.

[Dylan Pruitt]

I started stuttering around age 3. Throughout elementary school was in speech therapy.

[Emily Kwong]

An estimated 1 in 100 people have a stutter, according to the National Institute of health. That's 3 million Americans, but it is still an understudied condition. Dylan told us that even in college, there wasn't a lot of robust scientific knowledge about stuttering, what causes it, and why some people who start stuttering in childhood eventually stop while others do not.

[Dylan Pruitt]

I had kind of heard like, oh, there was some new studies that were looking at genetics of stuttering and reached out to a professor and asked some questions and he was like, you know, honestly, this is a very new area. I don't know a lot about it, but it's an area that needs a lot more research.

[Emily Kwong]

So Dylan decided this was it. This was the research he wanted to pursue. And while it was frustrating that there.

[Dylan Pruitt]

Were very few answers, it was another way, kind of inspiring realizing that I could take action and pursue this field of study and really contribute to the field.

[Emily Kwong]

Alongside geneticist Piper Belo and her team of researchers at Vanderbilt University, Dylan recently released a paper that is making waves within the field. Published in the journal Nature Genetics, the study identifies 57 genetic regions linked to stuttering and what other conditions stuttering may be related to. Today on the show, a breakthrough in stuttering research, how a simple 23andMe survey led to new genetic insights and directly challenges misconceptions about what causes stuttering in the first place. I'm Emily Kwong, and you're listening to Shortwave, the science podcast from npr.

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[Emily Kwong]

Okay, so to learn about the genetics of stuttering, I called up both Piper Belo and Dylan Pruitt, who worked on this study. I started by asking them. Okay, you guys, what's the main research question you were hoping to answer?

[Piper Belo]

Yeah, there has been an awareness for a very long time that stuttering is a trait that is very enriched in families. Meaning that if you are a person who stutters, you have a much higher likelihood of having a second or third individual in your family who also stutters than you would expect by chance. But another really common explanation is that there's some environmental exposure that is common to everyone within a family or within a household. And so in this case, we were really interested in tackling this question of whether or not we see this clustering of stuttering within families as a result of genetic factors. And so we were very excited to be able to try to pinpoint the specific genes and variants that were contributing.

[Emily Kwong]

And to pursue this question, you needed a massive data set that connected stuttering to genetics. You can't just, like, find one out there with a search on the Internet. Where did you get one?

[Piper Belo]

Yeah, that's a great question. So we have been working on this question for, gosh, 15, 20 years now. But after years and years and years had only amassed about 1500 or 2000 people who stuttered, it became apparent to me that in order to give this research the same sort of power for discovery as what we see being published every day for traits like diabetes or Alzheimer's disease or obesity, we would need to find a biobank that we could tap into that could provide both data on stuttering and genetic information at a really large scale. And it was so exciting when a colleague of mine sent me a message. She was at a research conference. She saw a poster being presented that had a snapshot of some Questions from the 23andMe survey for people that consent to research.

[Emily Kwong]

This being the genetic ancestry testing Service, for people to figure out, like, where are their families from secret cousins they never knew they had Kind of stuff.

[Piper Belo]

Exactly, exactly. So this direct to consumer Genetic testing company 23andMe had a question on their survey that was, you know, do you ever have, you know, have you ever had a stutter or a stammer?

[Emily Kwong]

It's pretty incredible. You really got the. The granddaddy of biobanks when it comes to stuttering research. No, really. And I understand that this study, what also makes it unique, in addition to having access to 1.1 million users via 23andMe, who reported whether they had ever had a stutter or had not, what also makes your study unique is that it was a genome wide association study. Dylan, what does that mean, a genome wide association study?

[Dylan Pruitt]

So it's a approach that is looking at areas of the. Of the genome that are kind of known to vary and then analyzing them to see if they are associated with a trait. You know, when we look at everybody that has this trait and everybody that does not have this trait, what are the handful of variants that are associated.

[Emily Kwong]

With that trait of, like, genetic variants?

[Dylan Pruitt]

Correct, correct.

[Emily Kwong]

So you're saying that through this process, you'd be able to see every single gene that's potentially linked to stuttering.

[Piper Belo]

Exactly right. Exactly right. And that led us to hypothesize maybe this is a trait that is more like the diabetes, obesity, height kinds of traits. And the genetic architecture of those have all been shown to be highly polymorphic. Meaning there's a large number of variants from all across the genome that all, you know, some might increase your risk a little bit, others might decrease your risk a little bit. You can almost think of it like you're putting sand on either side of a teeter totter, and eventually, if one side becomes heavy enough, then it flips and, you know, you have higher risk for this trait. And indeed, what we found was completely consistent with that hypothesis. We ended up revealing nearly 60 genomic regions across the whole human genome that were, you know, contributing small bits of additional risk of developing a stutter.

[Emily Kwong]

That must have been so gratifying. Were any genes real standouts for you as, like, playing an outsized role in contributing to the emergence of stuttering?

[Piper Belo]

Yes, absolutely. The day we got the summary results released by 23andMe and transferred over to us, and I opened the file to look at the results, I actually had to sit down because the number one gene that emerged from our study was this gene, VRK2. And the reason why that made me actually took my breath away was because VRK2, that gene, had just come out a few months prior as the Number one hit in a very large analysis of rhythm ability, people's ability to clap to a beat. And so this was the first time anybody actually had found a shared genetic underpinning underlying both developmental stuttering and this sort of rhythmicity, rhythm and musicality phenotype or trait.

[Dylan Pruitt]

Yeah, I mean, I think it was really intriguing. And not only was it found as a. As a top hit in the musical beat synchronization, but it was also the top hit in a couple of other independent studies that were looking at language as well. And so knowing that speech and language is so intricately tied and knowing that essentially the primary deficit in stuttering is really the timing of speech, it really blew me away. I think this gives us a really unique direction to explore.

[Emily Kwong]

I love this discovery because it suggests one of the potential genetic causes is a rhythmic difference. Like just the musicality of someone's speech is different. Not bad, just different.

[Dylan Pruitt]

Yeah, yeah. And I think that when you are caught in a moment of stuttering, it does feel like the inability to move forward or to push past a sound. And so having these external timing mechanisms that can increase fluency that might be generating some external cue that is lacking internally to a degree or is misaligned to a degree.

[Emily Kwong]

Okay. Are there any other notable genetic tidbits that emerged from this study? Any other associations beyond misalignment around rhythm?

[Dylan Pruitt]

Yeah, we observed positive correlation in males and females with depression. We also found correlations with autism and negative correlations with the beat synchronization. And so those are all features that we sometimes see associated with stuttering clinically. And so the genetic correlation is showing that there might be a genetic basis for those clinical associations that we see.

[Emily Kwong]

Do you think. Do you now think there might be different subtypes of stuttering?

[Piper Belo]

Oh, so there are different subtypes of stuttering. And this actually leads me back to what I was alluding to before about these really fascinating sex differences. So when kids turn about three, the onset of stuttering is approximately equal between girls and boys. But what's really interesting is that 80% of kids who stutter go on to recover, whether through therapy or spontaneous recovery. But most of those that recover are girls. And if you don't recover as a child, you are very likely to stutter for life. And this is what we call a persistent stutter versus a recovered stutter, which typically happens in fairly early childhood.

[Emily Kwong]

So are you saying the subtypes fall along biological sex lines?

[NPR Sponsor Announcer]

Yeah.

[Piper Belo]

Yeah, they do. And we don't understand why. You know, what is different about Girls and boys, especially, as they go through this transition around age 7 or 8. That explains this difference.

[Emily Kwong]

Dylan, going back to you, why does this research matter so much? And how can it support people who stutter?

[Dylan Pruitt]

I think that for decades, we've been trying to look at the stuttering puzzle by looking at the pieces in Isol. And so that's the behavioral patterns, the neural circuits for speech, the role of language. And each of these have given us valuable clues, but they haven't been able to connect the dots. And so one of my hopes is that genetics could offer a mechanistic framework or a way to see how these kind of separate domains are all interconnected and shaped by the underlying brain biology.

[Emily Kwong]

That's so interesting. Well, I gotta ask you this then, too. How do you hope this research then shapes treatment? Dylan, is this about finding a cure for stuttering?

[Dylan Pruitt]

Yeah, I don't really see our research as being about finding a cure for stuttering. I view our work is really about demystifying it. I think that stuttering is a beautiful and, in my view, underappreciated example of neurodiversity. And so our work helps us understand the genetic script behind that diversity. I think that instead of a one size fits all approach, perhaps we could move towards more personalized support strategies to tailor towards an individual's unique neurobiology. And this can be really powerful and maybe empowering for people who stutter and their fam and their families.

[Piper Belo]

Yeah, absolutely. I don't think of this as a discovery that is sort of closing the door on a chapter in stuttering. I feel like we just threw every door and window open. Right. This is us approaching a starting line, not a finish line.

[Emily Kwong]

Dylan and Piper, thank you so much for talking to us.

[Dylan Pruitt]

Thank you. It's really been a pleasure.

[Piper Belo]

Yeah, it's been really great to talk to you.

[Emily Kwong]

This episode was produced by Hannah Chin and edited by our showrunner, Rebecca Ramirez. Tyler Jones checked the facts. Kwesi Lee was the audio engineer. Special thanks to John Hamilton. Beth Donovan is our senior director, and Colin Campbell is our senior vice president of podcasting strategy. I'm Emily Kwong. Thank you for listening to short wave from NPR.

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