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What is stammering?

Stammering – or stuttering – is a relatively common speech problem that can occur in childhood and persist into adulthood.

Stammering is characterised by the repetition of sounds or syllables (such as saying ‘mu-mu-mu-mummy’), prolonging sounds (mmmmmmummy) and pausing or 'blocking' (when a word gets stuck or doesn't come out at all).

It usually occurs at the beginning of speech, and people will often avoid certain words or speaking situations to try to hide it.

Stammering varies in severity from person to person. A person might find that they have periods of stammering followed by times when they speak relatively fluently.

Read more about the

signs of stammering

Types of stammering

There are two main types of stammer:

  • Developmental stammering is the most common type of stammering that many people are familiar with. It develops during childhood as a child is first learning how to speak, and usually begins around the age of three-and-a-half years.
  • Acquired or late-onset stammering can occur in older children and adults as the result of a
    severe head injury
    or progressive neurological disease (disease affecting the nervous system). It can also be caused by certain drugs or medication, or psychological or emotional trauma.

The rest of this article will focus on developmental stammering.

Who is affected by stammering?

Stammering is common in young children. Estimates for developmental stammering vary, but it is expected that 5-8% of pre-school age children will experience a phase of non-fluent speech.

The condition is more likely to persist in males than females, which is why there are four times more men than women with a stammer. The reason for this is unclear.

All ethnic groups are affected equally by stammering.

The causes of stammering are still uncertain, but evidence suggests that inheriting certain genes may increase a child's likelihood of developing a stammer. Read more about the

causes of stammering

Treating stammering

About three in four cases of developmental stammering in pre-school children will resolve without treatment.

One in four children will need therapy to stop a persistent stammer developing. Treatment is highly successful in resolving stammers in pre-school age children, especially if it is received as soon as possible. Stammers are less likely to be totally eliminated in children over the age of six.

A speech and language therapist is trained to identify children whose stammers are likely to resolve naturally and which children need therapy, so early referral is key. Read more about

diagnosing stammering

Without adequate treatment, about 1% of older children and teenagers will have developed a persistent stammer. It is estimated that 1 in every 100 adults has a stammer.

Some adults find their stammering improves as they get older. Many will have learnt to control their stammer most of the time, although certain ‘triggers’ may make them stammer more, such as stress or having to speak in public.

There are many different speech and language therapy approaches to stammering that can help people to improve their fluency and communication skills.

Electronic ‘anti-stammering’ devices are also available and can be helpful for some people. These are designed to help people control their speech by giving them sound feedback.

Read more about

how stammering is treated

What causes stammering?

The exact cause of stammering is still unclear. Most experts think there are several possible factors that can trigger stammering in children.

These factors are described below.


Cases of stammering have been known to run in families. For example, if an identical twin has a stammer, there is a high chance that the other twin will also stammer.

This suggests that the genes a child inherits from their parents might cause them to stammer.

Research carried out in 2010 identified a number of specific genetic mutations (faulty genes) common in adults of Pakistani origin with a persistent stammer who had a family history of stammering.

It is unlikely there is one gene responsible for stammering. It is more likely that a problem in acquiring speech and language runs in families, which manifests itself in stammering behaviour.

There is evidence that stammering is four times more common in males than females. This links with other research about developmental disorders, which boys appear to be more likely to experience than girls. Girls are also more likely to see their stammers resolve naturally than boys.

Cognitive activity

Cognitive activity is a medical term used to describe many different mental processes that occur in the human brain.

Researchers have used

magnetic resonance imaging (MRI) scans
to study the brains of adults with a persistent stammer. MRI scans use strong magnetic fields and radio waves to produce a detailed image of the inside of the body.

The brain scans revealed that the pattern of cognitive behaviour was different in the brains of adults who stammer. In particular, there were:

  • low levels of activity in a part of the brain called the left temporal lobe, which is involved in processing sound and speech
  • unusually high levels of activity in the right hemisphere (in most adults, the left hemisphere is active when a person is speaking)

These results have led to a number of theories about how these abnormal patterns of cognitive activity may contribute to stammering.

First, the low levels of activity in the left temporal lobe may mean that a person has an impaired feedback system. This may cause differences in the way they hear their own voice.

Second, the abnormal activity in the right hemisphere may mean that a person who stammers has interference from this part of the brain when they are speaking.

However, it is unclear whether these effects are the result of stammering or the cause of stammering.

Basal ganglia

Another area of research has focused on a part of the brain known as the basal ganglia. The basal ganglia is responsible for some of the most basic human abilities and for processing powerful emotions such as fear and aggression.

Brain scans of adults who stammer have shown unusual activity in the basal ganglia. It may be that their stammering is caused by a problem with regulating the functions of the basal ganglia.

It is not known if this unusual cognitive activity is found in children who stammer, as no brain scans involving children have been carried out.

Stammering diagnosis

It is common for young children to have some degree of difficulty with their speech. If you notice that a child repeats certain words and sounds, or if they pause between words and sounds, it does not necessarily mean they have a stammer.

When to seek medical advice

An American organisation, the Stuttering Foundation of America, has created a questionnaire designed to help parents distinguish between normal speech problems and a stammer. The questionnaire consists of 10 questions:

  1. Does your child repeat parts of words rather than whole words or entire phrases, for example 'b-b-b-banana'?
  2. Does your child repeat sounds more than once every 8 to 10 sentences?
  3. Does your child have more than two repetitions, for example 'a-a-a-a-apple' instead of 'a-a-apple'?
  4. Does your child seem frustrated or embarrassed when he or she has trouble with a word?
  5. Has your child been stammering for more than six months?
  6. Does your child raise the pitch of their voice, blink their eyes, look to the side or show physical tension in the face when stammering?
  7. Does your child use extra words or sounds like 'uh', 'um' or 'well' to get a word started?
  8. Does your child sometimes get stuck so badly that no sound at all comes out for several seconds when they try to talk?
  9. Does your child sometimes use extra body movements, like tapping their finger, to get sounds out?
  10. Does your child avoid talking, use substitute words or stop talking in the middle of a sentence because they are worried they may stammer?

The more of these questions you answer 'yes' to, the more likely it is that your child has a stammer and may benefit from a referral to a speech and language therapist.

Speech and language therapy

A speech and language therapist (SLT) is a health professional who specialises in treating speech, language and communication disorders, including stammering. Your doctor will be able to refer you to your nearest speech and language therapy service.

While some cases of stammering may be easily diagnosed by listening to a child speak, it is recommended that parents consult an SLT if they have concerns.

The SLT will assess your child's speech and, if necessary, recommend a course of therapy specifically for your child, taking into account their speech presentation and stage of development.

It is important to note there is no evidence that parents cause their child's stammer.

Treating a stammer

There are many different treatments available for stammering, depending on a person's age and other individual factors.

Some of the most commonly used treatments are described below.

Demands and Capacities Model

It is still unknown why a child will start to stammer at a certain point. One model that tries to explain this is the Demands and Capacities Model.

The Demands and Capacities Model suggests that speech fluency can break down in a child with a tendency to stammer when the demands on their speech are greater than what they are able to produce.

These ‘demands’ are often made by the child, as they put pressure on themselves to communicate in a way that they can't yet manage.

The goal is to create an environment in which a child feels more relaxed and confident about their use of language. This involves:

  • speaking slowly to the child
  • developing a child-parent interaction
  • avoiding criticising or drawing attention to the child's stammer
  • trying to make the family environment as relaxing and calm as possible

Direct therapy

Most speech and language therapists (SLTs) may recommend direct therapy for cases of moderate to severe stammering that don't seem to be resolving over time.

A widely used type of direct behavioural therapy in the treatment of young children is the Lidcombe Programme.

The Lidcombe Programme is designed to be carried out by the parents of the child and is based on the principle of providing consistent feedback to the child about their speech in a friendly, non-judgemental and supportive way.

Stammering that persists beyond the age of six tends to be more challenging to resolve.

Other therapy options

There are other therapy options more appropriate for adults and those with acquired or late-onset stammering. These include psychological therapies and feedback devices.

Psychological therapies include solution-focused brief therapy (SFBT), personal construct therapy, neuro-linguistic programming (NLP) and

cognitive behavioural therapy
(CBT). These therapies are not used to treat stammering directly, but may be useful if feelings such as stress and
make stammering worse. During a course of CBT, your therapist may ask you what situations make your stammer worse, and your thoughts and feelings about those situations. Therapy programmes such as NLP can be helpful in providing confidence building techniques.

The British Stammering Association (BSA) has more information on all of the above alternative therapy options.

Feedback devices alter the way the voice is heard. They include:

  • delayed auditory feedback (DAF), which plays your voice back to you a fraction of a second after speaking
  • frequency-shifted auditory feedback (FSAF), which plays your voice back to you at a lower or higher frequency
  • combined DAF/FSAF devices, which use a combination of both methods

Signs of stammering

Developmental stammering usually involves some obvious outward signs, as well as some less obvious signs.

Outward signs of stammering include:

  • repeating certain sounds, syllables or words when speaking, such as saying 'a-a-a-a-apple' instead of 'apple'
  • prolonging certain sounds (not being able to move on to the next sound), for example 'mmmmmmmilk'
  • lengthy pauses between certain sounds and words, which can make it seem as though a child is struggling to get the right word, phrase or sentence out
  • using a lot of 'filler' words during speech, such as 'um', 'ah' and 'you know'
  • avoiding making eye contact with other people

Stammering can be worse in situations where the child is conscious of their speech and may be trying hard not to stammer. These situations might include:

  • talking to a person in authority, such as a teacher
  • giving a presentation at school or college in assembly or in class
  • reading aloud
  • speaking on the telephone
  • saying their name in registration at school

Associated behaviours

A child with a stammer can also develop some associated physical behaviours that can include involuntary physical movements such as eye blinking, jerking the head or jaw, clenching the teeth or fists, or body spasms.

Hidden signs may be:

  • deliberately avoiding saying certain sounds or words thought to provoke a stammer
  • avoiding social situations because of a fear of stammering, such as not asking for items in shops or not going to birthday parties
  • changing the style of speech to prevent stammering, for example talking very quickly or in an unusual tone of voice
  • feeling negative emotions such as fear, frustration, shame or embarrassment because of the stammer

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.