Stuttering Causes Anxiety, Not The Other Way Around

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Issue 1, Volume 112

By Andy Chen 

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Lee Reeves still remembers the frustration and embarrassment of being able to formulate words in his mind but being unable to get them out. Reeves, who stuttered from an early age, dreamt of becoming a veterinarian. However, Reeves’s stutter kept him from introducing himself when he was applying for a job at an animal hospital in high school. Today, Reeves is a veterinarian who also helps others as a national advocate for those with speech disorders.

Stuttering, a speech disorder characterized by involuntary repetitions and disruptions in the flow of speech, affects more than 70 million people worldwide. Though nearly five percent of children make up that number, a majority outgrow the disorder. The remaining make up one percent of adults, including President Joe Biden, actor James Earl Jones, actress Emily Blunt, and veterinarian Lee Reeves. Though these are all examples of successful people, stuttering often contributes to physical struggles and social anxiety as it attracts acts of discrimination and ridicule from others.

In the past, stuttering was associated with various causes, including tongue and voice box defects, emotional trauma, anxiety, and bad parenting. However, these misconceptions and myths have been disproven in recent years. Scientists have determined stuttering to be a neurodevelopmental disorder, and after years of studying the brains of people who stutter, they concluded that there are slight variations in the structure and function of the brains of those who stutter compared to those who don’t. These variations include neural connectivity differences, modifications in the speech and motor systems, and alterations in the activity of dopamine, a critical neurotransmitter that regulates emotions and movements, including the muscle movements necessary for speech.

According to neuroscientist Soo-Eun Chang from the University of Michigan, people who stutter tend to have weaker connections between areas of the brain responsible for hearing and for movements that produce speech. Chang also discovered slight variations in the structure of their corpora callosa, the collections of nerve fibers that connect the left and right hemispheres of the brain. These discoveries revealed that stuttering might be caused by delayed communication between different brain regions.

Chang has also been trying to understand why 80 percent of children who stutter recover from stuttering while the other 20 percent do not. To answer this, Chang and her colleagues began studying three year old children for up to four years. They found that compared to people who did not stutter, those who did had weaknesses in the integrity of the white matter —tissue in the brain made up of axons that transmit messages— that connects the auditory and motor areas in the left hemisphere. Those who recovered from stuttering displayed better organized white matter integrity as time passed, which is why there are stronger connections over time between areas of the brain in kids who lose their stutter. Thanks to this discovery, future research may study how white matter integrity can be used to identify severe stuttering or even ways to improve the organization of white matter.

While both children and adults who stutter have weaknesses on the left side of their brain, adults often exhibit a pattern of overactivity on the right side. The reason for this overactivity might be an effect of the brain adapting to the stutters. Despite this, much is still unknown about whether there are clear differences that indicate who will continue stuttering and who won’t.

However, research in the field of genetics might provide explanations for the root cause of stuttering. Two decades ago, geneticist Dennis Drayna of the National Institute on Deafness and Other Communication Disorders investigated the genes related to stuttering. He traveled to Pakistan, where intermarriage of cousins is common. This practice strengthens the influence of genes, making Pakistan the perfect place for Drayna to observe the effects of genes on stuttering.

In 2010, Dryna and his team identified mutations in three genes responsible for stuttering: GNPTAB (a gene related to other severe genetic disorders), GNPTG, and NAGPA. Drayna also received an e-mail from a man from Cameroon that inquired if genetics explained the prevalence of stutters in his family. After investigating the family in Cameroon, Drayna discovered a fourth stuttering gene, AP4E1. Drayna estimated that those four genes combined may account for 20 to 25 percent of stuttering cases. This high percentage indicates that these genes could be used to diagnose stuttering early on, allowing for proper therapy and a less severe case of stuttering.

Strangely, the identified genes are involved in transporting materials within the cell to the lysosome, where cellular waste is disposed of. In 2019, Drayna and his colleagues conducted another study and found that mice with the mutated GNPTAB gene had unusually long pauses when vocalizing, similar to stuttering. They identified fewer astrocytes, a type of brain cell in the corpus callosum, where white matter tracts connect the two hemispheres of the brain. This suggests that mutations in these lysosomal genes could connect genetics to the neurology of stuttering.

Recent research on the origin of stuttering is already providing the information needed for current and future stuttering therapies. Neuroscientist Gerald A. Maguire of the University of California, Riverside, School of Medicine, and his colleagues think that reducing dopamine activity in specific brain circuits can treat stutters. Maguire tested antipsychotic drugs such as risperidone, olanzapine, and lurasidone, all of which lowered dopamine activity and decreased the severity of stuttering, but none have been approved by the Food and Drug Administration (FDA). Sadly, those drugs also came with unwanted side effects such as impaired movement and weight gain.

Maguire is currently running clinical trials of another drug, called ecopipam, which targets a different group of dopamine receptors than the previous medications. Small studies also revealed that this drug had no notable side effects and helped improve the quality of life of its users. While this drug is promising, a single pharmacological treatment approved by the FDA will not work for everybody. As stuttering is caused by more than one condition, developing personalized medicine should be our next priority.

Another promising treatment for stuttering uses an electrical current to stimulate the brain. One group of researchers combined this technique with traditional speech therapies and received promising results. In the group that received the combination of treatments, the researchers found that stuttering decreased from 12 to 8 percent of their speech.

As we learn more about stuttering and its potential treatments, it won’t be long before people who stutter can live confidently, without stress or anxiety. Even the goals of therapies are changing. Instead of trying to erase stutters, new therapy aims to make stuttering easier to manage and accept, so people know how best to respond in situations where they do stutter. While scientists are linking together the neurology and genetics of stuttering and developing cures for it, the public should break down its prejudice against stuttering. And those who stutter should know that, just like Reeves, they too can realize their dreams.