Unravelling the biology of stuttering
FOR centuries people have feared being judged for stuttering, a condition often misunderstood as a psychological problem caused by things like bad parenting or emotional trauma. But research presented at a science conference recently explored its biological underpinnings: genetics and brain differences.
“By understanding the biology, we’re going to decrease the stigma. We’re going to increase the acceptance,” one of the speakers, Dr Gerald Maguire, said in a recent interview with The Associated Press. He’s a California psychiatrist who is involved in testing potential medications for stuttering based on the science.
Globally, 70 million people stutter, including US President Joe Biden, who has spoken publicly about being mocked by classmates and a nun in Catholic school for his speech impediment. He said overcoming it was one of the hardest things he’s ever done.
WHY DO PEOPLE STUTTER?
Stuttering has been documented from as far back as ancient China, Greece, and Rome. But no one really had any idea what caused it until modern genetic science and brain imaging began providing clues.
Researchers identified the first genes strongly linked to stuttering more than a decade ago. Imaging studies peered into the brains of adults and older children, and in the last few years, University of Delaware speech disorder researcher Ho Ming Chow started looking at three-to-five-year-olds. That’s around the age many kids begin stuttering, with about 80 per cent outgrowing it.
Chow said the imaging shows slight brain differences in young children who keep stuttering, compared with those who recover and those who never stuttered.
For example, Chow and his colleagues found genetic mutations related to stuttering are associated with structural abnormalities in the corpus callosum, a bundle of fibres that connects the two hemispheres of the brain and ensures they can communicate, and the thalamus, a relay station that sorts sensory information to other parts of the brain. Past research has also linked stuttering to the basal ganglia, brain structures involved in the coordination of movement.
“We know stuttering has a really strong genetic component,” Chow said. Though several genes may be involved and the exact genetic causes may vary by child, “they probably affect the brain in a similar way”.
Chow’s colleague Evan Usler stutters, and he likened it to “yips” or involuntary wrist spasms during golf. He said the latest evidence shows it’s a disorder of the cognitive control over speech.
Still, many people incorrectly believe people stutter because they are nervous, shy, or suffered childhood adversity, and if they just tried harder, they could stop.
“We have a long way to go” to change such beliefs, said University of Maryland researcher Nan Bernstein Ratner. “There’s still a lot of mythology out there.”
MOVING AHEAD, WITH ACCEPTANCE
Speech therapy is the mainstay of stuttering treatment. But the medicines currently being tested could be approved for stuttering in the next few years, first for adults and later for kids, said Maguire, who has stuttered since childhood.
Studies have suggested that stuttering may be related to excess levels of a chemical messenger in the brain called dopamine, and some turn down dopamine activity or block its action in a particular way.
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