I wish that I could give you a clear-cut answer on this, but unfortunately stuttering is a complex disorder. Even the smartest researchers out there are unclear about the exact cause of stuttering. Fact is, there is probably not just one cause of stuttering. Different factors may cause stuttering in different people. And in some cases, it can be helpful to think of stuttering as a symptom, and not a disorder in and of itself.
So what DO we know? To begin with, stuttering is sometimes a developmental challenge. This means that stuttering begins as young children are beginning to learn how to talk. Just like some kids have trouble learning to walk or write, some kids get tripped up when they are learning to talk. Stuttering usually appears when children begin stringing words together into sentences (not when they are just saying their first single words).
Research points to a complicated interaction between a child’s language development and development of speech-motor skills, combined with influences from the child’s genetic makeup, communication environment, and personality factors:
· Genetics - Some research suggests that there is a genetic component to stuttering, and stuttering does often run in families.
· Neurotransmitters – In some people who stutter, scientists have noted high levels of the neurotransmitter dopamine. An abundance of this brain chemical leads to overactivity in the muscle movement and coordination in all the body parts that help you speak.
· Auditory Processing - Auditory processing is when your brain interprets the sounds that came into your body through your ears. Some research results indicate that many people who stutter perform less well on various measures of auditory processing.
· Location of Brain Activity and Hemispheric Dominance - Neuroimaging studies (e.g., PET scans, fMRI) have shown abnormal patterns of brain activation in some people who stutter.
· Speech-Motor Function, Coordination & Timing/Rhythm – Some studies indicate that stuttering may involve some sort of breakdown in the speech-motor system. The research results are mixed depending on the tasks involved in each study. However, in some studies, people who stutter performed more poorly than non-stuttering individuals when completing tasks involving either motor timing skills (such as clapping or tapping to a particular rhythm) or complex motor actions with their face and mouth.