Stuttering is a speech disorder in which the normal flow of speech is disrupted by frequent repetitions or prolongations of speech sounds, syllables or words or by an individual's inability to start a word. The speech disruptions may be accompanied by rapid eye blinks, tremors of the lips and/or jaw or other struggle behaviors of the face or upper body that a person who stutters may use in an attempt to speak. Certain situations, such as speaking before a group of people or talking on the telephone, tend to make stuttering more severe, whereas other situations, such as singing or speaking alone, often improve fluency.
Stuttering may also be referred to as stammering, especially in England, and by a broader term, disfluent speech. Stuttering is different from two additional speech fluency disorders, cluttering, characterized by a rapid, irregular speech and spasmodic dysphonia, a voice disorder.
How is speech normally produced?
Speech is normally produced through a series of precisely coordinated muscle movements involving respiration (the breathing mechanism), phonation (the voicing mechanism) and articulation (throat, palate, tongue, lips and teeth). 
These muscle movements are initiated, coordinated and controlled by the brain and monitored through the senses of hearing and touch.
Before speaking, an individual takes a breath and the vocal folds (or vocal cords), which are two bands of muscular tissue located in the voice box directly above the trachea or windpipe, must come together. The air that is held in the lungs is gradually released, passing through the gently closed vocal folds thus causing vibration and producing the voice. The sound of the voice is passed through the throat and is directed into the mouth for most speech sounds, or into the nose for nasal sounds such as "m," "n" and "ng." The palate, tongue, jaw and lips move in precise ways to modify the sounds in order to make speech sounds.
Who stutters?
It is estimated that over three million Americans stutter. Stuttering affects individuals of all ages but occurs most frequently in young children between the ages of 2 and 6 who are developing language. Boys are three times more likely to stutter than girls. Most children, however, outgrow their stuttering, and it is estimated that less than 1 percent of adults stutter.
Many individuals who stutter have become successful in careers that require public speaking. The list of individuals includes Winston Churchill, actress Marilyn Monroe, actors James Earl Jones, Bruce Willis and Jimmy Stewart, and singers Carly Simon and Mel Tillis, to name only a few.
What causes stuttering?
Scientists suspect a variety of causes. There is reason to believe that many forms of stuttering are genetically determined. The precise mechanisms causing stuttering are not understood.
The most common form of stuttering is thought to be developmental, that is, it is occurring in children who are in the process of developing speech and language. This relaxed type of stuttering is felt to occur when a child's speech and language abilities are unable to meet his or her verbal demands. Stuttering happens when the child searches for the correct word. Developmental stuttering is usually outgrown.
Another common form of stuttering is neurogenic. Neurogenic disorders arise from signal problems between the brain and nerves or muscles. In neurogenic stuttering, the brain is unable to coordinate adequately the different components of the speech mechanism. Neurogenic stuttering may also occur following a stroke or other type of brain injury.
Other forms of stuttering are classified as psychogenic or originating in the mind or mental activity of the brain such as thought and reasoning. Whereas at one time the major cause of stuttering was thought to be psychogenic, this type of stuttering is now known to account for only a minority of the individuals who stutter. Although individuals who stutter may develop emotional problems such as fear of meeting new people or speaking on the telephone, these problems often result from stuttering rather than causing the stuttering. Psychogenic stuttering occasionally occurs in individuals who have some types of mental illness or individuals who have experienced severe mental stress or anguish.
Scientists and clinicians have long known that stuttering may run in families and that there is a strong possibility that some forms of stuttering are, in fact, hereditary. No gene or genes for stuttering, however, have yet been found.
How is stuttering diagnosed?
Stuttering is generally diagnosed by a speech-language pathologist, a professional who is specially trained to test and treat individuals with voice, speech and language disorders. The diagnosis is usually based on the history of the disorder, such as when it was first noticed and under what circumstances, as well as a complete evaluation of speech and language abilities.
How is stuttering treated?
There are a variety of treatments available for stuttering. Any of the methods may improve stuttering to some degree, but there is at present no cure for stuttering. Stuttering therapy, however, may help prevent developmental stuttering from becoming a life-long problem. Therefore a speech evaluation is recommended for children who stutter for longer than six months or for those whose stuttering is accompanied by struggle behaviors.
Developmental stuttering is often treated by educating parents about restructuring the child's speaking environment to reduce the episodes of stuttering. Parents are often urged to:
- provide a relaxed home environment that provides ample opportunities for the child to speak. Setting aside specific times when the child and parent can speak free of distractions is often helpful.
- refrain from criticizing the child's speech or reacting negatively to the child's disfluencies. Parents should avoid punishing the child for any disfluencies or asking the child repeat stuttered words until they are spoken fluently.
- resist encouraging the child to perform verbally for people.
- listen attentively to the child when he or she speaks.
- speak slowly and in a relaxed manner. If a parent speaks this way, the child will often speak in the same slow, relaxed manner.
- wait for the child to say the intended word. Don't try to complete the child's thoughts.
- talk openly to the child about stuttering if he or she brings up the subject.
Many of the currently popular therapy programs for persistent stuttering focus on relearning how to speak or unlearning faulty ways of speaking. The psychological side effects of stuttering that often occur, such as fear of speaking to strangers or in public, are also addressed in most of these programs.
Other forms of therapy utilize interventions such as medications or electronic devices. Medications or drugs which affect brain function often have side effects that make them difficult to use for long-term treatment. Electronic devices which help an individual control fluency may be more of a bother than a help in most speaking situations and are often abandoned by individuals who stutter.
Unconventional methods of stuttering therapy also exist. It is always a good policy to check the credentials, experience and goals of the person offering treatment. Avoid working with anyone who promises a "cure" for stuttering.
What research is being done about stuttering?
Stuttering research is exploring ways to improve the diagnosis and treatment of stuttering as well as to identify its causes. Emphasis is being placed on improving the ability to determine which children will outgrow their stuttering and which children will stutter the rest of their lives. Stuttering characteristics are being examined to help identify groups of individuals who have similar types of stuttering and therefore may have a common cause. Research is also being conducted that will help locate the possible genes for the types of stuttering that tend to run in families. Modern medical tools such as PET (positron emission tomography) scans and functional MRI (magnetic resonance imaging) scans are offering insight into the brain organization of individuals who stutter. The effectiveness of different types of treatment are also being examined, and new treatments are being developed.
Where can I get additional information?
NIH Pub. No. 97-4232
For more information, contact the NIDCD Information Clearinghouse.
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