Stuttering: Symptoms, diagnosis, and causes

Stuttering, also called stammering, is a speech disorder where an individual repeats or prolongs words, syllables, or phrases.

A person with a stutter (or stammer) may also stop during speech and make no sound for certain syllables. In this article, we explain the causes of stuttering, how it is diagnosed, and available treatments.

Fast facts on stuttering

Here are some key points about stuttering. More detail and supporting information is in the main article.

Stuttering affects more boys than girls.

In some cases, stuttering completely blocks an individual from producing a sound.

For an official diagnosis the individual will meet with a speech-language pathologist.

Most children with a stutter grow out of it.

Sometimes, a stutter can be the result of a head injury.

What is stuttering?

Woman whispering
Stuttering is a common problem, but in most cases, it can be overcome.

We all have the capacity, it may happen during a stressful job interview, talking to emergency services on the telephone, or during a presentation to a large crowd.

Stuttering is common when children are learning to speak and is an estimated five times more common in boys than girls. However, the majority of children grow out it. The speech disorder affects less than 1 percent of all adults.

For some, however, the problem persists and requires some kind of professional help, such as speech therapy.

Symptoms of stuttering

A person who stutters often repeats words or parts of words, and tends to prolong certain speech sounds. They may also find it harder to start some words. Some may become tense when they start to speak, they may blink rapidly, and their lips or jaw may tremble as they try to communicate verbally.

According to the American Speech-Language-Hearing Association, some individuals who stutter appear extremely tense or out of breath when they talk. Their speech may be completely “blocked” (stopped).

“Blocked” is when their mouths are in the right position to say the word, but virtually no sound comes out. This may last several seconds. Sometimes, the desired word is uttered, or interjections are used in order to delay the initiation of a word the speaker knows causes problems. Examples of interjections include such words as “um,” “like,” “I mean,” “well,” or “umm.”

Common signs and symptoms associated with stuttering:

Problems starting a word, phrase, or sentence.

Hesitation before certain sounds have to be uttered.

Repeating a sound, word, or syllable.

Certain speech sounds may be prolonged.

Speech may come out in spurts.

Words with certain sounds are substituted for others (circumlocution).

Also, when talking there may be:

rapid blinking

trembling lips

foot tapping

a trembling jaw

the face and/or upper body tightens

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Diagnosis of stuttering

Some aspects of stuttering are obvious to everyone, while others are not. To have a comprehensive and reliable diagnosis, the patient should be examined by a speech-language pathologist (SLP).

The SLP will note the types of problem the individual has when speaking, and how often problems occur. How the person copes with the stutter is also assessed.

The SLP may perform some other assessments, such as speech rate and language skills – this will depend on the patient’s age and history. The SLP will analyze all the data and determine whether there is a fluency disorder. If there is one, the SLP will determine to what extent the disorder affects the patient’s ability to function and take part in daily activities.

It is vital to try to predict whether a young child’s stutter will become long-term. This can be fairly accurately done with the help of a series of tests, observations, and interviews.

Assessments for older children and adults are aimed at gauging the severity of the disorder, and what impact it has on the person’s ability to communicate and function appropriately in daily activities.

Causes of stuttering

Experts are not completely sure what causes stuttering. We do know that somebody with a stutter is much more likely to have a close family member who also has one, compared with other people. The following factors may also trigger/cause stuttering:

Developmental stuttering

As children learn to speak, they often stutter, especially early on when their speech and language skills are not well developed. The majority of children experience fewer and fewer symptoms as this developmental stage progresses until they can speak flowingly.

Neurogenic stuttering

This is when the signals between the brain and speech nerves and muscles are not working properly. This may affect children, and can also affect adults after a stroke or some brain injury. The following may cause neurogenic stuttering:


head trauma

ischemic attacks – temporary block of blood flow to the brain


degenerative diseases, such as Parkinson’s


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