Understanding Stuttering

Stuttering, often called stammering in the UK and Ireland, is one of the most common speech differences in the world, and one of the most misunderstood. Here is a short overview of what stuttering is, who it affects, and what research says about it.

What is stuttering (stammering)?

Stuttering and stammering are two words for the same thing: a speech difference that interrupts the natural flow of speech. A person who stutters knows exactly what they want to say, but the words do not always come out smoothly. (NIDCD)

Stuttering can show up in different ways:

• Repetitions of sounds, syllables, or short words
• Prolongations, where a sound is stretched out
• Blocks, moments when no sound comes out despite effort

These moments can come with physical tension, such as tight lips or eye blinks, and many people learn to avoid certain words or situations. Stuttering also varies: it often increases on the phone or in front of a group, and usually disappears when singing or reading aloud together with someone else. (NIDCD; ASHA)

What causes stuttering?

There is no single cause. Researchers agree that stuttering comes from several factors working together. (ASHA; NIDCD)

• Genetics: stuttering runs in families. About 60% of people who stutter have a relative who stutters, and scientists have identified several genes linked to it. (Stuttering Foundation; NIDCD)
• How the brain handles speech: brain imaging shows consistent differences in how people who stutter plan and coordinate speech. (NIDCD)
• Development: children with other speech or language difficulties are more likely to stutter. (Stuttering Foundation)
• Environment: stress, time pressure, and a hectic pace can make stuttering worse, but they do not cause it. (ASHA; Stuttering Foundation)

What does not cause stuttering: nervousness, emotional trauma, or the way parents raise their children. (ASHA; Stuttering Foundation)

More than speech

Stuttering is about more than words. Many people who stutter feel anxious about speaking, avoid certain words or situations, or feel held back at school or work. Children who stutter are more likely to be bullied, and adults can face misconceptions and discrimination at work. (ASHA)

At the same time, many people who stutter describe strengths that grew from their experience, such as resilience, empathy, and a wish to help others. (ASHA) Good support looks at both: how you speak, and how you feel about speaking.

How you can help when someone stutters

A few simple things make conversations easier for anyone who stutters or stammers: (NIDCD; Stuttering Foundation)

• Give them time, and do not finish their words or sentences.
• Listen attentively and focus on what is said, not how it is said.
• Skip advice like “relax” or “slow down”; just keep the conversation going.

Knowledge pages: how we see stuttering patterns

In our approach, stuttering occurs in patterns, and the patterns can be identified and retrained. These pages describe our perspective in more detail. They sit alongside the research overview above, which also covers genetic and neurological factors.

Sources and further reading

General information

• Stuttering, National Institute on Deafness and Other Communication Disorders (NIH)
• Practice Portal: Stuttering, Cluttering, and Fluency, American Speech-Language-Hearing Association
• Stuttering facts and information (FAQ), The Stuttering Foundation
• Five myths about stuttering, The Stuttering Foundation
• Stuttering: myths, beliefs and straight talk, The Stuttering Foundation

Research on treatment

• Bothe et al., 2006: Stuttering treatment research 1970–2005: I. Systematic review incorporating trial quality assessment of behavioral, cognitive, and related approaches. American Journal of Speech-Language Pathology, 15(4), 321–341
• Baxter et al., 2016: Non-pharmacological treatments for stuttering in children and adults: a systematic review and evaluation of clinical effectiveness, and exploration of barriers to successful outcomes. Health Technology Assessment (NIHR), 20(2)
• Brignell et al., 2020: A systematic review of interventions for adults who stutter. Journal of Fluency Disorders, 64, 105766
• Carey et al., 2010: Randomized controlled non-inferiority trial of a telehealth treatment for chronic stuttering: the Camperdown Program. International Journal of Language & Communication Disorders, 45(1), 108–120
• Neumann et al., 2005: Cortical plasticity associated with stuttering therapy. Journal of Fluency Disorders, 30(1), 23–39
• Kell et al., 2009: How the brain repairs stuttering. Brain, 132(10), 2747–2760