Stuttering affects about 1% of adults. It is a speech disorder characterized by involuntary repetitions of syllables or words, prolongation of sounds, or blocks. It may also be accompanied by secondary behaviours such as closing the eyes or contracting facial muscles. Stuttering affects the motor aspect of speech: the person knows what he or she wants to say but has difficulty getting the words out. Stuttering is more common in men than in women: there are about four men for every woman who stutters. It also has a significant genetic component.

For several decades now, two major themes have developed simultaneously in an attempt to identify the causes of stuttering: genetic predisposition and the distinctive neurological features of people who stutter. Although emotional or environmental factors can influence stuttering, it is primarily a biological difference, not a psychological one.

Over the past 15 years, research on stuttering has led to the identification of genetic predispositions for this speech disorder in families with a high prevalence of stuttering. Researcher Dennis Drayna’s work, among others, has identified not just one gene, but mutations in multiple genes that are likely involved in the onset of persistent developmental stuttering. Mutations identified in the GNPTAB gene in particular were intricately linked to people who stutter in certain families with a high prevalence of stuttering.

Other researchers suggest that stuttering is the result of neuromotor speech system instability, which could be explained by poor connectivity between different parts of the brain to produce speech. However, in neuroimaging studies, the question remains as to whether these features are present prior to the onset of stuttering, or whether certain features are a consequence of having lived with the disorder and are in fact adaptations to stuttering. Furthermore, stuttering is part of a wider range of neurological disorders such as developmental language disorder, dyslexia, and verbal dyspraxia.

The question is: how are genetic mutations and neurological features connected? The genetic mutations identified in developmental stuttering involve genes responsible for trafficking enzymes to certain intracellular organelles, particularly the lysosome, a sac of enzymes that could be described as a protein recycling bin in the cell. Genetic linkage data, coupled with recent results obtained in animal models, confirm that these genetic variations contribute significantly to the susceptibility of developing persistent developmental stuttering in families where these mutations prevail. 

Drayna’s team published an article in 2019 showing that mice bearing a mutation in the GNPTAB gene showed anatomical changes, especially in the corpus callosum, which connects the two cerebral hemispheres. This article supports the hypothesis of an existing link between certain mutations in the GNPTAB gene and neurological features. 

In addition, preliminary research addressing both genetic mutations and neurological features is shedding new light. The work of Drs. Chow and Chang suggests that lysosome dysfunction in the cell could lead to changes in brain anatomy and function. These subtle changes are seemingly associated with vulnerability for developing stuttering. Stuttering is likely to appear in early childhood since rapid brain development at this age increases the need for optimal functioning of brain cells.

Sources: Onslow, M. (2020, may). Stuttering and Its Treatment: Eleven Lectures. Retrieved from: (à venir)

Chow & Chang (2020) Imaging genetic research in stuttering: connecting the dots, retrieved from:

Thank you to speech therapist Anne Moïse-Richard for her significant contribution to this text.

It appears that speech-language intervention is a key element in the prognosis of a person who stutters. The general consensus among speech-language pathologists is that if a person’s developmental stuttering persists into adulthood, they can never get rid of it completely. Young children have a much more favourable prognosis.

However, improvement is possible at any age. Through speech-language therapy, the person can improve fluency, further develop ease of speech, feel more comfortable while speaking and fully participate. In short, adult therapy should not be viewed as a means of eradicating stuttering, but rather a way of developing effective strategies to improve communication and ultimately enhance the well-being of the person who stutters.

Thank you to speech therapist Anne Moïse-Richard for her significant contribution to this text.

To learn more about this topic, we invite you to listen to episode 7 of «Je je je suis un podcast,» which deals with intervention approaches for adults who stutter (in French only).

The short answer is no, it is not too early to see a speech-language pathologist. Early identification of stuttering and appropriate treatment can reduce its long-term personal and social impacts.

The long answer comprises two components: 1) differentiate stuttering from normal disfluency at a preschool age, and 2) early speech-language pathology intervention in preschool children.

Differentiating Normal Disfluency From Stuttering at a Preschool Age.  

First, the speech-language pathologist will evaluate the child’s speech to determine whether they are experiencing normal disfluencies related to language acquisition, or whether the child is stuttering. The therapist will analyze several factors such as the number of repetitions and the frequency or type of disfluencies. Disfluency can be best defined as an interruption in speech.

Normal disfluency

Many children between the ages of 2 and 6 have a period when their speech is less fluent due to language and speech development. They learn to use increasingly longer and more complex sentences. This learning process, along with other factors, can result in less fluent speech. These may include certain conversational contexts where the speaking turn is more difficult to obtain (e.g., at the table or in the presence of other children) or certain emotions experienced (e.g., fear or excitement). 

Children whose disfluencies are considered «normal» and «non-stuttering» might, for example, use interjections (e.g., I want a… uh… ball), correct their sentences (e.g., Where’s my… Give me my ball) or repeat words (e.g., I want a… a ball). It is worth mentioning that «normal» repetitions are said at a moderate to slow speech rate, as if the child was thinking about what they want to say. These repetitions are not accompanied by excess tension or movements. Generally, the child is rarely aware that they hesitated, corrected a sentence or repeated a word.


However, some preschoolers do, in fact, stutter. In these cases, the disfluencies are not necessarily related to speech and language learning. The onset of stuttering may occur anywhere between 18 months and early puberty, but more often between the ages of 2 and 4, and, more specifically, just before the age of 3. In fact, the odds of developing a stutter after the age of 4 are low, estimated at about 5%. Stuttering is characterized by the frequent occurrence of disfluencies «typical of stuttering» such as blocks, audible prolongations, repetitions of one-syllable words and/or repetitions of parts of words. Some excess tension and associated movements may also manifest themselves during speech.

Early Speech-Language Pathology Intervention in Preschool Children

Following the assessment, if the speech-language pathologist determines that stuttering is present, he or she may: 1) begin treatment immediately or 2) document the child’s fluidity over a certain period, since the stuttering may disappear naturally without treatment. However, if stuttering severity does not decrease, the speech-language pathologist will begin treatment.

Various factors influence the decision of whether or not to take action immediately in preschool years. These include family history of persistent stuttering, the child’s gender, the presence or absence of other difficulties and their nature, etc. For information purposes: if there is a family history of persistent stuttering, the odds that the child will continue to stutter without speech and language treatment are approximately 65%. The speech-language pathologist may choose to intervene quickly in the following cases: when the stutter bothers the child, when they feel less comfortable speaking or when their parents are concerned about it. It is generally recommended that a child who has started stuttering before the age of 4 should have follow-up speech-language therapy before the age of 5. In fact, according to some studies, treatment to reduce the frequency of stuttering is believed to be more effective in children under the age of 6.

The parent will be involved in the process of speech-language therapy regardless of the severity of the preschooler’s stuttering. The aim is to improve fluency, to ensure the child’s ease when expressing themselves and to help them enjoy communicating. Also, communication hygiene strategies can be taught to the important people in the child’s life, such as the parents or the daycare educator. For example, they may be advised to respect speaking turns, to address the child by speaking more slowly, to focus on the message they want to convey rather than on the way they say it, to let them finish their stuttering moment rather than finish a word or sentence for them, etc. In any case, the speech-language pathologist will be able to guide the parent in the most appropriate treatment based on the individual needs of the child and their family.

Sources :

Guitar, B. (2014). Stuttering: An Integrated Approach to Its Nature and Treatment (4e éd.). Lippincott Williams & Wilkin.

Pertijs, M.A.J., Oonk, L.C., Beer, de J.J.A., Bunschoten, E.M., Bast, E.J.E.G., Ormondt, van J., Rosenbrand, C.J.G.M., Bezemer, M., Wijngaarden, van L.J., Kalter, E.J.,Veenendaal, van H. (2014).

Clinical Guideline Stuttering in Children, Adolescents and Adults.NVLF, Woerden.

If you have any questions, please feel free to direct them to the following e-mail address:

We look forward to hearing from you!

Thanks to Stéphanie G. Vachon, speech-language pathologist and member of ABC, for writing this column, and to Judith Labonté, speech-language pathologist and member of ABC, for her proofreading.

First, it would be interesting to get more information on the accident, particularly if medical diagnoses have been made afterwards (e.g., traumatic brain injury). In this case, it would still be worth considering the following hypotheses: acquired neurogenic stuttering and psychological stuttering. Indeed, the onset of the stuttering occurred suddenly in adulthood and is associated with an accident that may have caused neurological damage and/or represented a traumatic psychological event. However, it is important to ensure that it really constitutes stuttering, and that the disfluencies¹ following the accident are not caused by memory or language problems. Disfluency could be a temporary consequence of an impact to the brain. Acquired neurogenic stuttering and psychological stuttering remain uncommon fluency impairments. They differ from developmental stuttering² in their causes, speech symptoms, treatment, and emotions experienced in relation to communication.

¹Disfluencies: These are interruptions in speech. They can be typical of stuttering (blocks, audible prolongation, repetition of parts of words, repetition of one-syllable words) or normal, referring to other disfluencies (interjections such as um, uh, like, you know; sentence revision, repetition of a part of a sentence, repetition of multisyllabic words). These other disfluencies manifest themselves in the majority of speakers and are not frequent.   

²Developmental stuttering: Most people who stutter have developmental stuttering. It usually appears between the ages of 2 and 5, but can also appear during school age. The cause is neurophysiological, i.e., related to the functioning of the brain. 

Sources: Guitar, B. (2014). Stuttering: An Integrated Approach to its Nature and Treatment (4e éd.). Lippincott Williams & Wilkins.

Beausoleil, N. (2014, hiver). ORA – 3557: Évaluation du bégaiement [course notes].

Thank you to Stéphanie G. Vachon, M.P.O., for writing this column.

Absolutely! It is entirely possible to become a speech-language pathologist even if you stutter. It can even become an asset. Take, for example, empathy. The personal background of people who stutter or have stuttered can help them understand their client’s experience regarding the impacts of stuttering or any other communication-related issue. They may have received speech-language pathology services and can base themselves on their own experience as a client.  They can also associate what they teach to real-life situations they have faced themselves and share them if they wish, and if this is relevant to the progress of the intervention.

In fact, many speech-language pathologists famous for their contribution to fluency are also people who stutter. Consider, for instance:   

Dr. Charles Van Riper, pioneer of professional speech pathology and world-renowned expert on stuttering, who had developed an interest in the subject because of his own stuttering. In 1939, he published one of the first books in the field of communication science and its disorders: Speech Correction: Principles and Methods (9 editions), followed in the early 1970s by The Nature of Stuttering, and The Treatment of Stuttering. 

Barry Guitar, Ph.D., an expert speech-language pathologist internationally recognized for his research on stuttering and its intervention. He is Professor Emeritus at the University of Vermont and is himself a person who stutters. His areas of expertise and research examine stuttering treatments for preschool children, as well as stuttering temperament and recovery in both children and adults. He has also published Stuttering: An Integrated Approach to Its Nature and Treatment (5 editions), which is widely used in university courses on fluency.

In addition, several of the people who stutter who were interviewed in the When I Stutter documentary are also speech-language pathologists. One example in the film is a speech therapist’s intervention with a young man who stutters. This is Gail Wilson Lew, M.A., recognized by the American Speech-Language-Hearing Association (ASHA) as an expert in fluency disorders. She is also a professor at the University of California, where she teaches courses on fluency.


American Speech-Language-Hearing Association Archives. Charles Van Riper.

American Speech-Language-Hearing Association. Joel Korte: Using Experience as a Person who Stutters to Help Others . YouTube.

Essman Franz, J. L. (2018, May 17). Celebrating Barry Guitar, Ph.D., CCC-SLP. The University of Vermont.

Wilson Lew, G. Gail Wilson Lew. Linkedin.

Thank you to Stéphanie G. Vachon, M.P.O., for writing this column, and to speech therapist Ariane Saint-Denis, who is part of the stuttering team at the Centre de réadaptation Marie Enfant – CHU Sainte-Justine, for proofreading. 

The best advice for interacting with someone who stutters is probably to ignore the stuttering. See the person for who they are, focus on what they are saying. Don’t pay attention to the stutter. In fact, author and journalist Katherine Preston, also a person who stutters, gives on her website her best advice on how to interact with those who stutter:

  • Go beyond the stutter. Listen to what people who stutter say rather than the way they say it. Interact with them as you would with anyone.
  • Don’t hesitate to reach out to people who stutter. Don’t raise your eyebrows or look away.
  • Maintain eye contact.
  • Be patient: the words will come out. It might simply take a few seconds longer than it would for someone who doesn’t stutter. And, by the way: the person who stutters doesn’t need you to say the words for them.

“There have been many myths surrounding the nature or origin of stuttering. And as with any foreign concept, these beliefs have spread,” writes Marie-Claude Monfrais-Pfauwadel in her book Bégaiement, bégaiements : un manuel clinique et thérapeutique. We could not have explained it better: many stereotypes about stuttering need to be dismantled, first because they undermine the people who stutter who are eager to learn to accept themselves and to better manage their condition, but also because they deprive society of the richness of another’s differences. 

Here are some of the most persistent stereotypes: 

Stuttering is caused by childhood trauma. 

FALSE: Epidemiology has clearly shown that people who stutter have not experienced more childhood trauma than people who do not stutter. 

Stuttering is caused by stress. 

FALSE: Stress does not cause stuttering, although in some cases, it can modulate or accentuate it. 

People who stutter are less intelligent than others. 

FALSE: There’s no connection whatsoever between intelligence and stuttering. 

Stuttering can be resolved easily with therapy. 

FALSE: For the most part, speech-language pathologists agree that persistent developmental stuttering (i.e., stuttering that began in childhood and continues into adulthood) can never go away completely. However, certain techniques can improve fluency and help the person be more comfortable with their speech. Essentially, in the case of persistent developmental stuttering, therapy should not be viewed as a way to eradicate stuttering, but rather to develop effective strategies to improve the person’s communicational abilities and well-being.