Speech-Language Therapy

Nineteenth-century roots

Judy Duchan's history of speech-language pathology, hosted by the University at Buffalo, argues that the field's origins lie earlier than the founding of its professional organization in the 1920s. She identifies three overlapping influences: the elocution movement, the scientific revolution and the rise of professionalism. Elocutionists worked with orators, politicians, singers, preachers and actors, and some, including Andrew Comstock and Alexander Graham Bell, also gave lessons to people with speech, language or hearing problems.

The same account notes that brain studies by Paul Broca and Carl Wernicke formed part of a shift from religious and philosophical explanations toward scientific ones. It states that nineteenth-century America had no allied health professions of any kind, including speech-language pathology, and that services were offered by self-described practitioners, some of whom had overcome speech problems of their own or had talents in teaching or public speaking.

Organization in the United States

The American Speech-Language-Hearing Association (ASHA) dates its history to an informal meeting of the National Association of Teachers of Speech in New York City in 1925, where some members wanted to promote scientific, organized work in speech correction. The American Academy of Speech Correction was established in December 1925. The body was renamed in 1927, 1934, 1947 and 1978, when it took its current name, and it began developing national certification standards in 1952.

Accounts of the founding differ in detail. The Buffalo history associates the usual dating with a meeting convened by Edward Lee Travis in Iowa City, whereas ASHA's own history describes the New York meeting. The ASHA account is used here, and a reviewer may wish to check the founding details against ASHA's archives. ASHA reports 25 charter members and 247,000 members in 2025.

Profession and title

The profession carries different titles by country. ASHA uses speech-language pathologist (SLP), and its scope-of-practice document calls SLPs autonomous professionals who are the primary providers of speech-language pathology services. The Royal College of Speech and Language Therapists (RCSLT) in the United Kingdom uses speech and language therapist (SLT). In everyday usage the shorter term speech therapy is common, although the professional bodies' areas of practice extend well beyond speech sounds.

Clinical labels used in research

Labels for children's language difficulties changed after a multinational Delphi consensus study (CATALISE) with a panel of 57 experts. It recommended Language Disorder for a profile of difficulties that causes functional impairment and a poor prognosis, and Developmental Language Disorder (DLD) when the disorder is not associated with a known biomedical cause. It also agreed that DLD does not require a gap between verbal and nonverbal ability.

Other terms also vary. Aphasia is an acquired language impairment after brain damage that can affect speech, comprehension, reading and writing. A Cochrane review notes that stuttering is called stammering in some countries. A German guideline proposed renaming common developmental stuttering 'originary neurogenic non-syndromic stuttering', a proposal that is specific to that guideline and not a general standard.

Areas of practice

ASHA's 2016 scope of practice lists, without claiming to be exhaustive, fluency (stuttering and cluttering), speech production, spoken and written language, cognition, voice, resonance, feeding and swallowing, and hearing-related habilitation and rehabilitation. It describes evidence-based practice as combining current high-quality research with practitioner expertise and the client's values and preferences.

The RCSLT describes therapists as assessing, diagnosing and helping people understand and manage difficulties with speech, language, communication, eating, drinking and swallowing. Its examples include babies with feeding problems, children with language difficulties, and adults after stroke, brain injury, Parkinson's disease, dementia or head and neck cancer.

Settings and working relationships

ASHA names early intervention, schools, health care, community programs, higher education and private practice as settings. The RCSLT lists hospitals, schools and nurseries, prisons, care homes, community clinics and clients' homes. Therapists work directly with clients and carers, and with teachers, nurses, occupational therapists and doctors to develop treatment programs. The sources reviewed do not describe a standard session format, which varies by condition, age and setting.

Intervention formats named in the research

Trials give examples of delivery. In the Lidcombe Program for young children who stutter, a parent and child attend a clinic and the parent is taught to carry out treatment at home; one trial in a Cochrane review conducted visits by telephone. A US Preventive Services Task Force evidence report describes parent group training programs of 6 or 11 sessions for children with speech and language delay. These are trial descriptions and not a general protocol.

Uses described by the professional bodies

The professional bodies describe uses across the lifespan: language and speech sound difficulties in childhood, stuttering, voice difficulties, language and cognitive-communication difficulties after stroke or brain injury, and feeding and swallowing problems in infants, children and adults. These are statements of scope by the bodies themselves. They define what the profession covers and do not report that every use has been tested in trials.

Uses with a research base and uses without one

Four areas have systematic reviews or guidelines: aphasia after stroke, developmental language disorder and language delay, stuttering, and swallowing difficulty after stroke. Evidence for each concerns a specific population and intervention and does not extend to the profession's other areas. For example, the aphasia reviews address adults after stroke, and the swallowing review addresses people within six months of a stroke.

The sources reviewed for this page did not examine other areas listed in the scope of practice, such as voice, resonance or cognitive rehabilitation outside stroke. The absence of such sources here reflects the search and should not be read as showing that those uses lack evidence or that they have been shown to be effective.

Aphasia after stroke

A Cochrane review of speech and language therapy for aphasia after stroke (searches to 2015) included 57 randomized trials with 3,002 participants. Compared with no therapy, therapy was associated with better functional communication (standardized mean difference 0.28, 95% confidence interval 0.06 to 0.49), reading, writing and expressive language, although benefits were not evident at follow-up in the smaller number of studies that measured it.

The same review found better functional communication with therapy at higher intensity, higher dose or longer duration, but higher dropout in those groups. A 2025 European Stroke Organisation guideline, using GRADE, recommended a total dose of at least 20 hours based on low-quality evidence, and suggested higher intensity, individually tailored therapy and digital and group delivery.

Developmental language disorder and language delay

The US Preventive Services Task Force evidence report (searches to January 2023) found 17 randomized trials with 1,517 children aged 5 or younger on interventions for speech and language delay or disorder. Two trials of relatively intensive parent group training (11 sessions) found benefits on measures of expressive language, and one trial of a six-session program found no difference. The report found evidence on other interventions limited.

The CATALISE consensus sets terminology and is not a trial. An author commentary describes DLD as a category useful for identifying children who may benefit from therapy services, but not a well-defined condition. The sources reviewed do not allow a statement about therapy effects across the whole DLD population.

Stuttering

A Cochrane review of non-pharmacological interventions for stuttering in children aged six or younger found four trials with 151 children, all comparing the Lidcombe Program with a wait list. Stuttering frequency was lower with the program (mean difference -2.16 percent syllables stuttered, 95% confidence interval -3.48 to -0.84), but certainty was very low and risk of bias high. The program is designed to take one to two years, and no participant had completed it at any measurement point.

A 2021 review of eight trials in children and adolescents found both direct (Lidcombe) and indirect approaches reduced stuttering in preschool children, with no high-level evidence for school-age children or adolescents. A German guideline reported good evidence for speech restructuring in adolescents and adults, and found the evidence did not support hypnosis or unspecified eclectic therapies.

Swallowing difficulty after stroke

A 2026 Cochrane update on swallowing therapy in acute and subacute stroke included 181 randomized trials with 11,500 participants. Behavioral interventions may reduce swallowing impairment (standardized mean difference -1.17, 26 trials) and chest infection or pneumonia (odds ratio 0.45, 8 trials), but certainty ranged from very low to low. The authors cite small trials at high or unclear risk of bias, publication bias and inconsistent results.

Limits that run across the reviews

Several limits recur. Trials are often small, populations and doses vary, and the term therapy covers many techniques, so pooled results describe bundles of interventions and not a single method. In the aphasia review, benefits were not evident at follow-up in the studies that measured it. Blinding of participants is generally not possible with behavioral therapy, and several stuttering and swallowing reviews note high or unclear risk of bias.

Gaps in the evidence base

The US Preventive Services Task Force report found no study that directly assessed the benefits and harms of screening for speech and language delay. The 2021 stuttering review reports no high-level evidence for school-age children or adolescents. The Cochrane stuttering review calls for independent researchers to evaluate other interventions. No source reviewed here ranks the profession's areas of practice against one another.

Harms reporting

Harms are poorly documented. The US Preventive Services Task Force report states that no randomized trial of speech and language interventions in young children reported on harms, and the Cochrane stuttering review found no included trial reporting adverse effects. In the aphasia review, higher-intensity and higher-dose therapy was associated with more dropout, and the authors note such programs may not be acceptable to all. The sources reviewed do not allow a statement about the frequency of adverse events.

Care boundaries

Swallowing difficulty after stroke is associated, according to the Cochrane review, with death or dependency, pneumonia and longer hospital stay, so it is a reason for medical assessment. Sudden loss of speech or understanding, or new swallowing problems, call for urgent medical assessment. Therapy does not replace medical care for causes such as stroke. This page is educational and does not give individual advice.

Training and professional standards

In the United States, ASHA's 2020 standards for the Certificate of Clinical Competence in Speech-Language Pathology require a master's, doctoral or other recognized postbaccalaureate degree from an accredited program, 400 supervised clock hours, a national examination, and a clinical fellowship of at least 36 weeks. Certificate holders must follow ASHA's Code of Ethics and complete professional development hours in each three-year period.

In the United Kingdom, the RCSLT states that the title speech and language therapist is protected and that therapists must be on the register kept by the Health and Care Professions Council, while titles such as communication therapist are not protected. Requirements differ by country, and other jurisdictions were not reviewed.