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Section 2 - What is Stammering?

What is Stammering / Stuttering?

Stammering is a struggle to get words out. Typical features of stammering include repetition of sounds / words, prolonging initial sounds / words or not being able to produce any sound. Stammering is often accompanied by physical tension in the face and body. 

Stammering is a variable and unpredictable condition. People who stammer can often experience periods of fluent speech but may also struggle to speak at other times.

People who stammer may avoid words or situations they feel will increase their likelihood of stammering. In some people who stammer, they may avoid things to such an extent that their stammer will be completely hidden. This is known as "interiorised" or "covert" stammering.

Stammering is often compared to an iceberg: there is a lot going on underneath the surface which others do not see. The visible part of the stammer includes repetition of sounds/words, pronologing initial sounds, and being unable to produce sounds. Under the surface part of the stammer includes avoidance, negative thoughts, and feelings such as frustration, embarrassment and shame. These hidden features have a role in maintaining the stammer. Both visible and hidden features are addressed in therapy.        

Stuttering iceberg

What causes stammering?

Stammering is not caused by one single factor. For each person, there are a number of factors which:

  • contribute to their vulnerability to stammering.


  • contribute to whether their stammer is likely to continue.

In young people and adults, there are 5 main areas which may contribute to stammering. These are:

  • Neurophysiology - in some adults who stammer, there are differences in the way their brains are structured or how they work, compared to adults who do not stammer.
  • Pharmacological - stammering can occur as a side-effect of medication or recreational drug use.
  • Psychogenic - stammering may arise from a psychological response to stress or trauma.
  • Re-occurrence of a childhood stammer - a childhood stammer may re-emerge when coping strategies are no longer working for that person.
  • Idiopathic - any contributing reasons to the stammer are not known.

In children, young people and adults, there are also some factors which may contribute to the occurrence of stammering. These are:

Linguistic factors - stammering is more common at the beginning of sentences, and in sentences with long and complex structures.

  • Sex - stammering occurs more frequently in males.
  • Environmental factors - events or things in the environment can acts as stressors which may coincide with the start of stammering, or stammering becoming more severe.


Royal College of Speech and Language Therapists. (2018). Introduction to dysfluency. Retrieved from

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