Home Biologist salary Unraveling the Biology of a Mysterious Disease: Stuttering

Unraveling the Biology of a Mysterious Disease: Stuttering


Holly Nover grew up trying to hide her stutter.

“I was very embarrassed,” said the 40-year-old mother from St. Johns, Fla., whose 10-year-old son Colton also has a speech impediment. “So I developed habits of changing my words so it wouldn’t be noticed.”

For centuries people have feared being judged for stuttering, a condition often misunderstood as a psychological problem caused by things like poor parenting or emotional trauma. But the research presented at a scientific conference on Saturday explores its biological underpinnings: genetics and brain differences.

“By understanding biology, we will reduce stigma. We will increase acceptance,” said one of the speakers, Dr. Gerald Maguire, in a recent interview with The Associated Press. He is a California psychiatrist who is involved in testing potential drugs for stuttering based on science.

Worldwide, 70 million people stutter, including President Joe Biden, who has publicly said he was mocked by classmates and a nun at a Catholic school for his speech impediment. He said overcoming it was one of the hardest things he’s ever done.

After a campaign event in 2020, his struggle came to the fore when he met a New Hampshire teenager who also stuttered. Brayden Harrington said after his dad told him about Biden, he wanted to introduce himself and shake hands. They ended up talking for an hour.

Living with a stutter hasn’t been easy, Brayden said, recalling a particularly difficult moment years ago when he got caught up in words reciting the Gettysburg speech in class and then is went home and cried.

“I want to continue what Joe Biden told me,” he said. “That it doesn’t define you and that you can be so much more than you see yourself.”


Stuttering has been documented as far back as ancient China, Greece and Rome. But no one really had a clue what caused it until modern genetic science and brain imaging began to provide clues.

Researchers identified the first genes strongly linked to stuttering more than a decade ago. Imaging studies have scrutinized the brains of adults and older children, and in recent years, University of Delaware speech disorders researcher Ho Ming Chow has begun to suitable for children from 3 to 5 years old. Many children start to stutter around age, with about 80% outgrowing it.

Chow said imaging shows slight brain differences in young children who continue to stutter, compared to those who recover and those who never stutter. He was scheduled to discuss his research Saturday at the American Association for the Advancement of Science conference.

For example, Chow and his colleagues found that genetic mutations linked to stuttering are associated with structural abnormalities in the corpus callosum, a bundle of fibers that connects the two hemispheres of the brain and ensures that they can communicate; and the thalamus, a relay station that sorts sensory information to other parts of the brain. Previous research has also linked stuttering to the basal ganglia, brain structures involved in coordinating movement.

“We know that stuttering has a very strong genetic component,” Chow said. Although several genes may be involved and the exact genetic causes may vary from child to child, “they probably affect the brain in the same way”.

Chow’s colleague, Evan Usler, stutters, and he has compared it to “yips,” or involuntary wrist twitches, during golf. He said the latest evidence shows it is a cognitive control disorder of speech.

Yet many people mistakenly believe that people stutter because they’re nervous, shy, or suffered from childhood adversity — and if they just tried harder, they might quit.

“We have a long way to go” to change these beliefs, said University of Maryland researcher Nan Bernstein Ratner. “There’s still a lot of mythology there.”


Speech therapy is the mainstay of treatment for stuttering. But drugs currently being tested could be approved for stuttering in the next few years, first for adults and later for children, said Maguire, who has stuttered since childhood.

Studies have suggested that stuttering may be linked to excessive levels of a chemical messenger in the brain called dopamine, and some reduce the activity of dopamine or block its action in a particular way.

Nover, a speech therapist active with the National Stuttering Association, said many people would surely be interested in trying stuttering medication — but not her. She is happy with her life as it is and has come to terms with her stutter, she said. If Colton was struggling and wanted to try drugs as a teenager, she would be open to the idea.

Brayden, now 14, would not.

Taking drugs is “just taking away part of you…taking away part of your personality,” he said.

If it wasn’t for his stutter, he says, he wouldn’t have dreamed of becoming a speech therapist when he grew up. He wouldn’t have written a children’s book to inspire others. And he wouldn’t have overcome the challenges that made him brave.


The Associated Press Health and Science Department is supported by the Howard Hughes Medical Institute Department of Science Education. The AP is solely responsible for all content.