Researchers Find Genetic Cause for Stuttering

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Stuttering has baffled scientists for thousands of years, but a new study has brought researchers closer to understanding this medical mystery. Researchers from the National Institute of Deafness and Other Communication Disorders have found three genetic mutations in the brain cells of people who stutter.

Over 200 Pakistani citizens – many of whom were family members - and 550 people from the United States and England were involved in the study. Approximately half were stutterers.

The gene mutations occurred in chromosome 12 and are called GNPTAB, GNPTG and NAGPA. They are located in cells in the part of the brain that controls speech and are involved in a process called cell recycling. These defected genes are thought to account for about 9% of the total cases of stuttering.

Stuttering or stammering is a disruption in the normal flow of speaking. For people with the disorder, certain syllables may be delayed, prolonged or repeated and for some may be accompanied by facial tics. It affects approximately 3 million people in the United States, according to data from the National Institutes of Health. About 60% have a close family member with the disorder.

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Stuttering is usually first seen in children between the ages of 2 and 5, when they are learning to speak. Boys are more likely to be affected than girls. Most outgrow the condition, though about 1% continues to stutter into adulthood. Speech therapy is currently the most common treatment.

People have historically thought of stuttering as being emotional in nature – a condition perhaps brought on by stress. Recognizing that stuttering is a biological disorder can bring better understanding to those afflicted.

The discovery could lead to a more specific diagnosis and treatment for the disorder. “People who are helped by one type of therapy might for instance be the people with mutations in one of these genes, whereas the people who are helped by another therapy are people with mutations in another gene that we’ve identified,” said study author Dennis Drayna.

A possible treatment, according to Drayna, is enzyme replacement therapy, where a drug containing the missing or defective enzyme is given to people with the disorder. Other possible treatments currently being studied are the schizophrenia drugs Risperdal and Zyprexa and a medication called pagoclone, used to treat anxiety and panic disorders.

The study is published in the New England Journal of Medicine.

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