Facts and causes

Facts about stammering

• stammering is a a neuro-developmental issue that typically first emerges between 2;6 and 3 years of age
• the same number of boys and girls start to stammer but girls are more likely to stop stammering so that in the adult population there is a ratio of 4-5 men for every woman who stammers
• approximately 1% of adults stammer

What causes stammering?

Genetics

Stammering tends to run in families. If there is someone in your immediate or extended family, who used to stammer or who still does, then that suggests an inherited vulnerability.

It is likely that there are several genes involved in stammering.

Genetics does not entirely account for stammering. Studies of identical twins are shown that one can stammer while the other does not. This shows that other factors are involved in determining whether stammering emerges or not.

Brain function

Brain imaging studies have shown that people who stammer have subtle differences in the way that the brain has developed. There are differences the way that the brain processes speech signals, and also some small differences in the structure of some parts of the brain. This can be seen in children as young as three years of age. These differences are likely to be key in understanding why stammering develops for some people.

Speech motor skills

Research has shown that, as a group, people who stammer tend to be slightly slower at making the movements involved in speaking, for example getting voice started in the larynx or moving from one speech sound to the next. The implication of this is that speaking rapidly potentially puts a lot of pressure on a speech motor system that is not able to manage rapid speech easily. This can destabilise the speech motor system and result in more stammering. Taking time pressure off, for example by speaking a little more slowly, is often helpful.

Environmental or situational factors

People who stammer often say that they stammer less when things are going fairly smoothly in life and when they are speaking in relaxed situations, for example when speaking with people who know them well, when they are not under time pressure, or when on a 1:1. Conversely people may stammer more in situations where there is more time pressure, when speaking to groups of people, or when there is an element of pressure in terms of making a good impression or performance.

Personality or temperament and emotions

Stammering is not caused by anxiety. Young children who stammer are not more anxious than those who do not stammer, however anxiety can develop when young people have experience of people reacting negatively to them stammering. Some, but not all adults who stammer experience high levels of anxiety in situations where they feel that they will be judged by how fluently they speak. Where this is the case it can be an important aspect to explore in therapy.

Language skills

If someone has any difficulties with language skills, for example difficulty thinking of the words they want or organising their ideas into spoken language, then this can disrupt the overall speech system. Using more pauses can help give you more planning time if this is the case.

Acquired stammering

Sometimes people start to stammer later in life when they have never stammered before as a child. When this happens it is because of either a neurological issue (i.e. arising from a stroke or neurological disease) or because of extreme distress or psychological trauma. A speech therapist can be involved in the multi-disciplinary care of individuals with an acquired stammer.

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