What causes stuttering?
The exact cause of stuttering is unknown. Recent studies suggest that genetics plays a role in the disorder. It is thought that many, if not most, individuals who stutter inherit traits that put them at risk to develop stuttering. The exact nature of these traits is presently unclear. Whatever the traits are, they obviously impair the individual's ability to string together the various muscle movements that are necessary to produce sentences fluently.
Not everyone who is predisposed to stutter will develop the disorder. For many, certain life events are thought to "trigger" fluency difficulty. One of the triggers for developmental stuttering may be the development of grammar skills. Between the ages of 2 and 5 years, children learn many of the grammatical rules of language. These rules allow children to change immature messages ("Mommy candy") into longer sentences that require coordination to produce fluently ("Mommy put the candy in my backpack"). A child who is predisposed to stutter may have no difficulty speaking fluently when sentences are only one or two words long. However, when the child starts trying to produce longer, more complex sentences, he or she may find himself or herself not quite up to the challenge—and disfluent speech results.
After stuttering has started, other factors may cause more disfluencies. For example, a child who is easily frustrated may be more likely to tighten or tense speech muscles when disfluencies occur. Such tension may increase how long a disfluency lasts. Listeners' responses to stuttering (e.g., teasing) can aggravate fluency difficulties as well. People who stutter vary widely in how they react to the disfluencies in their speech. Some appear to be minimally concerned. Others—especially those who have encountered unfavorable reactions from listeners—may develop emotional responses to stuttering that hinder speech production further. Examples of these emotions include shame, embarrassment, and anxiety.
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How common is stuttering and when does it typically start?
Usually, the symptoms of developmental stuttering first appear between the ages of 2½ and 4 years. Although less common, stuttering may start during elementary school. Stuttering is more common among males than females. Among elementary school-age children, it is estimated that boys are three to four times more likely to stutter than girls. Preschoolers may show little or no awareness of their speech difficulties, particularly during the early stages of the problem. Throughout the school years and beyond, however, most people who stutter become increasingly aware of their speech difficulties and how others react when they do not speak fluently.
The development of stuttering varies considerably across individuals. Some children show significant difficulty with speech fluency within days or weeks of onset. Others show a gradual increase in fluency difficulties over months or years. Furthermore, the severity of children's stuttering can vary greatly from day to day and week to week. With some children, the disfluencies may appear to go away for several weeks, only to start again for no apparent reason. For teens and adults who stutter, the symptoms of stuttering tend to be more stable than they are during early childhood. Still, teen and adult speakers may report that their speech fluency is significantly better or worse than usual during specific activities.
About 75% of preschoolers who begin to stutter will eventually stop. Many children who "recover" from stuttering do so within months of the time their stuttering started. Nonetheless, there are some people who have stuttered for many years and then improve. Why some people recover is unclear, and it is not possible to say with certainty whether the stuttering symptoms for any particular child will continue into adulthood. Children's recovery from stuttering may happen when they receive speech therapy. The role of speech therapy in the recovery process needs to be studied further, however, because some preschoolers appear to recover without ever having seen an SLP. It is hoped that, with continued research, SLPs will someday be able to precisely answer questions about why and how recovery takes place, both with and without speech therapy.
To contact a speech-language pathologist, visit ASHA's Find a Professional.
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The ASHA Leader articles on stuttering
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See Also:
Stuttering
Stuttering: Benefits of Speech-Language Pathology Services