National Stuttering Association

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No one speaks perfectly all the time—we all experience disruptions in our speech. For people who stutter, these disruptions, or disfluencies, are more severe and experienced more consistently. For some, stuttering goes away in childhood, for others, it persists throughout adulthood. Why is this?

Researchers currently believe that stuttering is caused by a combination of factors, including genetics, language development, environment, as well as brain structure and function[1]. Working together, these factors can influence the speech of a person who stutters.

Stuttering and Language Development

Stuttering most often begins between the ages of two and four, when children’s speech and language abilities are rapidly expanding. During this period of rapid growth, interactions between speech, language, and emotional development are hypothesized to influence the development and persistence of stuttering. As children produce longer and more complex sentences, their brain experiences higher demand. This cognitive demand can affect motor planning control necessary to produce fluent speech.

Brain Activity in People Who Stutter

While no one factor determines stuttering, the predominate theory suggests that a combination of genetics, language development, and the environment can influence the brain activity of people who stutter.

The areas of the brain responsible for language may look and work differently in people who stutter. Findings from brain imaging studies indicate that there is more right hemisphere activity in adults who stutter, with less activity in the left hemisphere areas typically responsible for speech production. Some people who stutter have more difficulty processing auditory information and slower reaction times on sensory-motor tasks. In general, research has shown that the pathways in the brain responsible for language look and function differently when stuttering occurs.

Characteristics associated with stuttering persistence

Between 5% and 8% of all preschool aged children will develop stuttering; however, 80% of these children will stop stuttering during early childhood [2]. Certain clinical characteristics have been associated with persistence and recovery of stuttering. Specifically, research suggests that children who are male, have a family history of stuttering, are older at stuttering onset, exhibit a higher frequency of stuttering-like disfluencies, produce speech-sound errors, and demonstrate lower expressive and receptive language skills are more likely to continue stuttering [3].

Genetic Factors

Family histories of stuttering demonstrate that stuttering runs in families and is influenced by genetic factors. Children who stutter, for example, often have relatives who stutter. Identical twins sharing the exact same genetic makeup have more similar patterns of stuttering than fraternal twins. We also know that stuttering affects males more than females and that females are less likely to continue stuttering as adults.

Researchers haven’t pinpointed a specific gene that’s solely responsible for stuttering. However, it’s possible that if you carry certain genetic material, you may be more likely to stutter.

Emotions and the Environment

If children begin encountering negative reactions to their disfluencies or face an increased number of communication challenges, negative feelings surrounding their communication may develop. Negative feelings and attempts to hide or prevent stuttering may increase tension and further affect their ability to communicate. Depending on their temperament, some children may experience more anxiety when speaking and negative feelings towards communication than others. Although emotional factors, nervousness, and anxiety do not cause stuttering, they may place an additional cognitive burden on children who stutter during a critical period of language development.

Acquired Stuttering

Most people who stutter begin stuttering in childhood, during the developmental period in which they are learning to communicate. In more rare cases, stuttering is the result of brain injury or severe psychological trauma. This form of stuttering, known as “acquired” stuttering, differs from developmental stuttering in both its causes and manifestations.

Common Myths

There are many Common Myths that include theories about what causes stuttering. It’s important to remember that no single cause has been found for stuttering:

  • Stuttering is not caused by children’s parents
  • Stuttering is not caused by pointing out a child’s disfluencies
  • Stuttering is not a psychological problem (although it may have psychological effects)
  • Stuttering is not a sign of brain injury or reduced intelligence
  • Stuttering is not caused by learning another language (although it may present differently in bilinguals)
  • Stuttering is not caused by nervousness or anxiety

Most importantly, stuttering is no one’s fault!

Original material provided by: Leslee Dean, M.A. in Latin American Studies, MS-SLP student at Florida International University and Angela M. Medina, Ph.D., CCC-SLP. Revisions provided (01.2024) by Caitlin Franchini, MS, CCC-SLP and  Dr. Megan M. Young, CCC-SLP.

[1] Smith, A. & Weber, C. (2017). How stuttering develops: The multifactorial dynamic pathways theory. Journal of Speech, Language, and Hearing Research60(9), 2483-2505.

[2] Yairi, E., & Ambrose, N.(2013). Epidemiology of stuttering: 21stcentury advances.Journal of Fluency Disorders, 38(2), 66–87.https://doi.org/10.1016/j.jfludis.2012.11.002

[3] Singer, C. M., Hessling, A., Kelly, E. M., Singer, L., & Jones, R. M. (2020). Clinical characteristics associated with stuttering persistence: A meta-analysis. Journal of Speech, Language, and Hearing Research, 63(9), 2995-3018.