What Causes Stuttering? Experts think that a variety of factors contribute to stuttering, including: Genetics: About 60% of those who stutter have a close family member who stutters. Other speech and language problems or developmental delays. Differences in the brain's processing of language: People who stutter process language in different areas of the brain. And there's a problem with the way the brain's messages interact with the muscles and body parts needed for speaking.
