About 3 million Americans are affected by stuttering, a speech disorder that involves sounds that are repeated or held for too long.

Scientists are learning about what causes people to stutter, and genes tell a big part of the story.

Researchers are still working to fully understand what causes stuttering, but they do know that it often runs in families. Its 15 times more likely that a sibling of a person who stutters will stutter than a random person in the population, explains Dr. Dennis Drayna, an National Institutes of Health expert on the genetics of communication disorders

Stuttering affects about 1 in 20 children with many able to outgrow the disorder on their own or with the help of a professional called a speech-language pathologist.

However, about 2025% of children who stutter will continue into adulthood, says Drayna. This condition is known as persistent developmental stuttering. Overall, about 1% of adults stutter, and its much more common in men than women.

By studying families with multiple people who stutter, Drayna has identified several genes that can cause stuttering. Mutations in these genes have now been found in people around the world who stutter and these studies suggest that genes likely play a role for many people who stutter.

All the genes identified so far are involved intracellular trafficking, a process inside the cell that helps direct things in the cell to their proper locations. Problems with intracellular trafficking have recently been recognized in other neurological disorders, like Parkinsons and Alzheimers disease. But more research is needed to understand how it impacts speech and stuttering.

For those who stutter, communicating with others can be difficult which affects relationships, self-esteem, and quality of life as well as leading them to avoid talking. Stuttering often gets worse if theyre feeling tired or anxious.

People with stuttering know exactly what they want to say. Theyre just unable to say it at the rate they would like, Drayna said.

Its common for people who stutter to be able to speak without stuttering when in a low-stress environment, according to NIH. For example, they may have no problem speaking fluently with a pet, baby, or singing in a group.

Scientists are also using brain imaging scans to better understand brain activity in people who stutter which may help show why some children outgrow stuttering as well as hopefully lead to better treatments one day.

For now, treatment for stuttering involves therapy, aimed at making speech smoother or avoiding issues that worsen stuttering, with a speech-language pathologist.

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Why do we stutter? Scientists study genetic causes and treatment options - WLNS