In the largest genetic investigation of its kind, scientists have uncovered 57 regions of the genome associated with stuttering. The findings now provide the clearest picture yet of the biological roots of a condition affecting tens of millions of people worldwide.
The study analyzed DNA from more than 1.1 million individuals and reveals that stuttering shares genetic ties with other brain-related traits, including autism, depression, and an unexpected link: musical rhythm.
“This is the first time we’ve been able to see the broad, complex genetic landscape of stuttering,” said Jennifer Below, a geneticist at Vanderbilt University Medical Center and senior author of the study. “Rather than being caused by personal or familial failings or intelligence, our study shows that stuttering is influenced by our genes.”
Is Stuttering Mostly Genetic?
Stuttering — characterized by repetitions, sound prolongations, and speech blocks — has often been misunderstood, blamed on nervousness or parenting. It affects roughly 1% of adults globally, and about 5% of children, many of whom recover naturally. But for some, the disorder persists into adulthood, sometimes shaping the course of their lives.
The causes of persistent stuttering have remained elusive. Partly because the condition doesn’t cause physical illness or death, it has historically received little research funding.
That began to change when Below noticed an interesting question in 23andMe’s consumer genetic survey: “Have you ever had a stammer or stutter?” So, she and collaborator Shelly Jo Kraft of Wayne State University leapt at the chance to work with the company’s vast dataset.
Their analysis included 99,776 people who said “yes” to that question and over one million who said “no.” The researchers further divided the participants by sex and genetic ancestry, creating eight groups in total.
By examining millions of genetic variants, they identified 57 genomic regions, which scientists call ‘loci’, strongly associated with stuttering. These mapped to 48 genes and differed between men and women. As such, the data hinted at sex-specific mechanisms for why males are more likely to have persistent stuttering.
Genes, Music, and the Brain’s Rhythm
Among the most notable findings was the appearance of a gene called VRK2, previously linked to beat synchronization or the ability to keep a rhythm, like clapping to music. That gene was the strongest signal in men with stuttering.
“This gene was also implicated in a study of language decline in Alzheimer’s disease,” Below said. “Historically, we’ve thought of musicality, speech, and language as three separate entities, but these studies suggest there might be a shared genetic underpinning.”
This supports what some scientists have called the “Atypical Rhythm Risk Hypothesis”. It proposes that difficulties processing rhythm could be a core trait in several speech and language disorders, including stuttering.
Clinicians have long observed that stuttering often decreases when people speak in sync with a metronome or sing. This new evidence offers the first strong genetic support for that rhythm-based connection.
Previously, twin studies have shown that stuttering is commonly inherited, making a strong genetic basis very likely. This new study confirms that genetic risk is widespread across the population — not just limited to rare mutations within families.
Stuttering’s Genetic Overlap with Autism and Depression
Beyond music, the researchers uncovered genetic links between stuttering and several neurodevelopmental and psychiatric conditions.
“There are significant genetic correlations with autism and depression,” said Dillon Pruett, a postdoctoral fellow at Vanderbilt and co-author of the study. “And what’s striking is that these correlations appear across both sexes.”
Using statistical tools called Mendelian randomization, the team even found potential two-way causal relationships between stuttering and some of these traits. This suggests not only shared genetics, but also potentially interwoven biological pathways.
In females, stuttering appeared to causally influence the risk of developing ADHD. In both sexes, higher body mass index and depression showed bi-directional relationships with stuttering.
While this new paper focused on common genetic variation in the general population, a previously published but related 2023 study led by researchers in Australia zoomed in on a single family.
Following a four-generation pedigree with multiple cases of persistent stuttering, researchers at the University of Melbourne and Murdoch Children’s Research Institute identified a rare variant in a gene called PPID. The gene is involved in a “chaperone pathway,” which helps shuttle proteins to their proper places in cells.
Brain scans of affected family members revealed subtle structural anomalies in speech-related brain regions, particularly the corticospinal tracts. Remarkably, mice engineered with the same PPID mutation developed similar brain changes.
“This is the first time we’ve seen a direct link between a genetic mutation and structural brain differences in people who stutter,” said Professor Angela Morgan, who leads Australia’s first speech genomics clinic. “It’s a huge step forward.”
A Polygenic Portrait
The new study went further. The team developed polygenic risk scores, which are composite genetic scores based on a person’s variants. They then tested whether they could predict stuttering in two independent cohorts.
The male-specific risk scores performed best, successfully distinguishing people who stuttered from controls in both cohorts. Female-specific scores worked, too, but with less predictive power. This may reflect differences in recall or recovery, as more girls recover from childhood stuttering than boys.
“It may be that what we’re measuring in females in the 23andMe data is differently confounded by recall compared to what we are measuring in men,” Below said. “We hope these results will motivate intricate, detailed future studies of stuttering recovery versus sex.”
Heritability estimates — how much of the variation in a trait is due to genetics — landed at around 9–10% based on common variants. That may seem modest, but it’s in line with what scientists have found for conditions like insomnia or type 2 diabetes.
While genetics is a significant factor, they are not the whole story. Yes, genes set the stage, but environmental factors likely help determine how and when symptoms appear — or resolve.
From Genes to Understanding (and Compassion)
For centuries, people who stutter have faced ridicule, misunderstanding, and discrimination. Myths have abounded, from the notion that bad parenting causes stuttering, to claims that it reflects anxiety, low intelligence, or lack of willpower.
The findings from this study offer a powerful rebuttal.
“We need to understand risk factors for speech and language traits so that we can identify kids early and get appropriate care for those that want it,” said Below. “There have been hundreds of years of misconceptions about what causes stuttering… our study shows that stuttering is influenced by our genes.”
Pruett, who also stutters, added: “There are a lot of unanswered questions about stuttering, and as someone personally affected, I wanted to contribute to this body of research. We hope to use this knowledge to dispel stigma.”
As the genetics of stuttering comes into focus, researchers call for deeper exploration into the biology of rhythm, into how brains develop speech fluency, and into how we can personalize care for those who stutter.
The findings were published this week in Nature Genetics.
