What are the Most Common Speech Disorders?

Speech disorders affect millions of people and their ability to communicate. According to the National Institute on Deafness and Other Communication Disorders (NIDCD), approximately 1 in 14 (7.2%) U.S. children ages 3 to 17 have had a voice, speech, or language disorder in the past 12 months. The prevalence is highest among the youngest children — about 10.8% of children ages 3 to 6 are affected. Some speech disorders can be overcome, while others are lifelong conditions. In either case, therapy with a speech pathologist can help a person make the most of their speech capabilities and develop alternative methods of communication.

Speech pathologists — also called speech-language pathologists (SLPs) or speech therapists — complete a master’s program to evaluate a person’s speech and communication, create a treatment plan, and provide intervention to improve communication. Some speech pathology careers focus on research and the development of evidence-based treatment guidelines for various speech and language disorders.

According to the American Speech-Language-Hearing Association (ASHA), speech refers to the production of sounds and words. Speech problems can include difficulty producing sounds clearly, a hoarse or raspy voice, or stuttering—repeating sounds or pausing unexpectedly when speaking.

Language is distinct from speech; it encompasses the words and systems we use to share ideas. Problems with language can include difficulty understanding others, talking, reading, or writing.

According to ASHA, a speech disorder is an impairment of sound articulation, fluency, or voice. It falls under the broader umbrella of communication disorders, which also includes language and hearing disorders.

There are three primary categories of speech disorders:

The medical community does not know the cause of every speech disorder, and for many conditions, the cause can vary. Potential causes include:

Childhood apraxia of speech (CAS) is a motor speech disorder in which disrupted signals from the brain prevent the muscles of the mouth and throat from moving correctly, even though those muscles are not weak. The child has difficulty planning and sequencing the precise movements needed for speech. According to ASHA’s Practice Portal on Childhood Apraxia of Speech, CAS can be idiopathic (no known cause), associated with a neurological condition, or occur as part of a complex neurobehavioral disorder. Emerging research has identified more than 30 genes — including FOXP2 and CDK13 — that may account for approximately one-third of CAS cases.

CAS will not resolve without intervention. With consistent, intensive speech therapy, a child’s speech can improve significantly. Effective treatment approaches emphasize movement-based techniques rather than sound-pattern drilling, and many incorporate sensory cueing. Augmentative and alternative communication (AAC) may also be part of a comprehensive treatment plan.

Also called verbal apraxia or dyspraxia, acquired apraxia of speech in adults results from brain damage caused by a stroke, traumatic brain injury, tumor, or oxygen deprivation. A person may make sound substitutions or omissions, struggle to move their lips, tongue, and jaw in a coordinated way, or be inconsistent in how they produce specific sounds. In severe cases, an adult may be unable to speak at all. Treatment is provided by a licensed SLP and typically involves intensive motor-based practice, often alongside treatment for co-occurring conditions such as dysarthria or aphasia.

Dysarthria is a motor speech disorder caused by weakness or paralysis of the muscles used for speech, resulting from damage to the brain or nervous system. People with dysarthria may slur words, speak too slowly or rapidly, speak very softly, or have difficulty controlling the muscles of their lips, tongue, and jaw. Severity varies widely; dysarthria may co-occur with other conditions, including apraxia of speech. Treatment focuses on improving speech intelligibility, breath support, and, when needed, introducing AAC strategies.

Orofacial myofunctional disorders (OMDs) are abnormal movement patterns of the oral and facial muscles that can interfere with the development of bones and muscles in the face and mouth. According to ASHA’s Practice Portal on Orofacial Myofunctional Disorders, OMDs can affect people of all ages and may interfere with breathing, swallowing, eating, and talking. Common contributing factors include anything that causes a person to rest their tongue incorrectly or keep their lips apart at rest, such as prolonged pacifier use, thumb sucking, and certain structural differences.

Tongue thrust — a pattern in which the tongue pushes forward during swallowing, drinking, or speaking — is one of the most frequently seen OMDs. OMDs are treated through orofacial myofunctional therapy (OMT), an interprofessional area of practice that often involves collaboration between SLPs, orthodontists, dentists, and other providers. OMT is generally not recommended for children under age 4, who may not yet have the self-monitoring skills needed to benefit fully.

A child who is unable to produce speech sounds correctly by age 4 may have a speech-sound disorder, also called a phonological or articulation disorder. Speech sound disorders are not limited to children; adults may have had a disorder since childhood or developed one following brain injury. A person with a speech sound disorder may substitute one sound for another, omit sounds, add sounds, or distort sounds to a degree that makes them difficult to understand. It is important to note that accents and dialects involve some of these same patterns and are not speech disorders.

According to research published in the field, the prevalence of speech sound disorders in 3-year-olds is estimated at around 15%, declining to roughly 4% by age 6 as many children naturally resolve early errors.

A person who stutters may repeat whole words or sounds, prolong sounds, or experience blocks — moments when words seem to “get stuck.” These patterns are known as repetitions, prolongations, and blocks. While most people stutter occasionally, stuttering becomes a disorder when it interferes with communication and leads to negative reactions, such as avoidance, anxiety, or reduced quality of life.

The exact cause of stuttering is not fully understood. Research points to neurological and genetic factors, and a family history of stuttering is common. Most children begin stuttering between ages 2 and 6; if it persists for more than 6 months, evaluation by an SLP is recommended. According to ASHA’s Practice Portal on Stuttering, Cluttering, and Fluency, contemporary treatment approaches increasingly take a “stuttering-affirming” perspective — focusing on building confidence, reducing avoidance, and improving overall communication quality rather than treating fluency as the sole goal.

Several conditions affect vocal function and communication ability. ASHA recognizes voice disorders as a clinical area in which SLPs play a central role. Common voice disorders include:

Aphasia is an acquired communication disorder caused by damage to the language-processing areas of the brain — most commonly the left hemisphere — typically following a stroke, traumatic brain injury, or other neurological event. According to the National Aphasia Association, aphasia impairs the ability to speak and understand others, and most people with aphasia also experience difficulty reading and writing. Aphasia does not affect intelligence. A person with aphasia may struggle to find words, use incorrect words, speak in incomplete sentences, or have difficulty understanding what others say. The severity and type of aphasia depend on the location and extent of the brain injury. SLPs work with individuals with aphasia to improve communication through direct language treatment, compensatory strategies, and AAC.

According to ASHA’s Practice Portal on Selective Mutism, selective mutism is a complex anxiety disorder — not simply shyness or willful refusal to speak. It is classified as an anxiety disorder in the DSM-5-TR (American Psychiatric Association, 2022) and is characterized by consistent failure to speak in specific social situations despite speaking comfortably in others. Onset typically occurs between ages 3 and 6, and the condition is often first identified when a child enters school. Prevalence estimates generally range from 0.2% to 1.6% among children. SLPs play an important role as part of an interprofessional team that often includes psychologists, psychiatrists, and school-based professionals. Behavioral approaches, including graduated exposure, are commonly used in treatment.

Children who are significantly delayed in developing speech and language skills may have a preschool language disorder. These delays may involve difficulty with receptive language (understanding directions, answering questions, following conversations), expressive language (naming objects, asking questions, forming sentences), or both. Early identification and intervention are critical. Research consistently shows that children with speech and language difficulties face a greater risk for challenges with literacy, academic performance, and social development. NIDCD data indicate that children with speech or language disorders are among those most likely to receive intervention services, with more than half of affected children ages 3 to 17 accessing some form of support.

Many speech disorders cannot be fully cured, but with speech-language therapy from a licensed SLP, most children and adults can meaningfully improve their communication abilities or successfully adapt to alternative methods.

SLPs use a wide range of evidence-based approaches depending on the disorder and the individual’s needs. Treatment may include teaching correct sound production and placement, building motor patterns for speech through repetitive practice, improving fluency and reducing communication avoidance, voice therapy to restore or compensate for vocal function, language-based interventions for aphasia and developmental language delays, behavioral approaches for selective mutism, and training in augmentative and alternative communication (AAC) when appropriate.

Depending on the disorder, SLPs often collaborate closely with physicians, psychologists, neurologists, educators, and other allied health professionals. Evidence-based practice — guided by current research, clinical expertise, and client and family values — is the foundation of SLP service delivery.

Speech disorders affect children and adults across all walks of life, but they do not have to stand in the way of communication, education, or career success. If you or someone you know is experiencing communication difficulties, a licensed speech pathologist can evaluate, diagnose, and treat a wide range of speech and language disorders.

Information last updated: April 2026

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