Speech and language therapy

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Augmentative and alternative communication. Methods of communication that are used to supplement or replace speech or writing for those with difficulties in the production or comprehension of spoken or written language.

Absolute effects

Absolute effects are differences between outcomes in the groups being compared. For example, if 10% (10 per 100) experience an outcome in one of the treatment comparison groups and 5% (5 per 100) experience that outcome in the other group, the absolute effect is 10% - 5% = a 5% difference.


Something that has developed at a point after birth.


An association is a link or connection between two or more things, it does not indicate that one thing causes another.

Autism Spectrum Disorder (ASD)

A disorder that affects how a person communicates with and relates to other people, and how they experience the world around them.

Average difference

The average difference is used to express therapy effects for outcomes such as perception of fluency or emotions experienced that are measured using a scale. It is the difference between the average value for an outcome measure in one group and that in the comparison group.

Baseline risk

Baseline risk is an estimate of the likelihood that an individual or group will experience a speech, language, communication or swallowing difficulty before therapy is given.


In treatment comparisons, to blind someone means to keep them from knowing who received which treatment.

Comparison of treatments

A comparison of treatments is a study where researchers look carefully at the differences in what happens between groups that use different treatments.

Confidence interval

A confidence interval is a range that reflects the extent to which the play of chance may be responsible for a result from a study, such as an effect estimate. There is a high probability (usually 95%) that the actual effect estimate is within that range.


In treatment comparisons, any factors other than the treatment being compared which may affect the speech, language, communication or swallowing outcomes being measured. For a factor to lead to confounding, it must differ between the treatment comparison groups, and affect the outcome of interest.


Present from birth


Formal identification of a clinical condition or difficulty.


A difficulty in the use of muscles required for to make speech sounds, which can appear as slurred or effortful speech.


Dysfluent speech is the disruption of the flow and timing of speech by repetition of sounds, syllables or words, sound prolongation and/or blocking on sounds. It is sometimes known as stammering.

Effect estimate

The most likely size of a treatment effect, based on the results of a study or a systematic review.


An effect of a treatment is what happens as a direct result of the treatment.


A treatment or intervention is effective if it causes something to happen that is wanted, e.g. achieving a goal in speech and language therapy.


"Evidence", in this context, is often referring to the findings from scientific research that is used to support what you believe or decide.

Fair comparison

A fair comparison of interventions is one where the only important difference between two or more groups of individuals that are compared is the intervention they receive.


Intervention is used throughout as synonymous with treatment, approach or therapy, and is any action intended to improve speech, language, communication or swallowing.


Professionals from different fields (e.g. physiotherapist, speech and language therapist, doctor) working together to treat an individual by using each of their areas of expertise


Relating to nerves and muscles e.g. a neuromuscular swallowing difficulty is a swallowing difficulty relating to nerves and muscles


Movements of the muscles of the face e.g. tongue, lips, jaw, mouth


In treatment comparisons, an outcome (or ‘outcome measure’) is something good or bad that can happen after a treatment and is measured in studies.


For effect estimates, the p-value is the probability (ranging from 0 to 1) that the results observed in a study could have occurred by the play of chance, if the intervention actually had no impact on the outcome.


Picture exchange communication system. A form of AAC often used by individuals with autistic spectrum disorder.

Placebo effect

Just believing that a treatment works can change how someone feels. This is called a placebo effect. Placebo effects are presumed to act psychologically through suggestion.


A placebo is a dummy or sham treatment that does not contain active ingredients, which has been designed to be indistinguishable from the active treatment(s) being assessed. It is used to blind participants and others involved in a study of treatment effects, and to reduce the risk of placebo effects.


A particular group of people sharing the same characteristics.


The document providing detailed plans for a study including what the researchers intend on finding out, how, and ways in which they will make their evaluation.

Relative effects

Relative effects are ratios. For example, if the probability of an outcome in the treatment group is 10% (10 per 100) and the probability of that outcome in a comparison group is 5% (5 per 100), the relative effect is 5%/10%.

Service user

Someone who is in receipt of speech and language therapy services.

Side effect

A side effect is a harmful or unpleasant effect of a treatment or therapy that is not planned.


Speech and language therapist; or speech and language therapy

Statistically significant

A “statistically significant” result is unlikely to have happened by chance. The usual threshold for this judgement is a probability of less than 5% (0.05).


A subgroup is a subdivision of a group of people; a distinct group within a group. For example, in studies or systematic reviews of treatment effects, questions are often asked about whether there are different effects for different subgroups of people in the studies, such as women and men, or people of different ages.

Surrogate outcome

Surrogate outcomes are outcome measures that are not of direct practical importance but are believed to reflect outcomes that are important. For example, blood pressure is not directly important to patients but it is often used as an outcome in studies because it is a risk factor for stroke and heart attacks.

Systematic review

A summary of studies addressing a clear question, using systematic and explicit methods to identify, select, and critically appraise relevant studies, and to collect and analyse data from them


Therapy is used throughout as synonymous with treatment, approach or intervention, and is any action intended to improve speech, language, communication or swallowing.

Tongue tie resection

A tongue tie is when the connection between the bottom of the tongue and the base of the mouth is too short causing problems with tongue movement. Surgery can be used to resect or correct this. 

Treatment comparison

A treatment comparison is a study where researchers look carefully at the differences in what happens between groups that use different treatments.


Treatment is used throughout as synonymous with therapy, approach or intervention, and is any action intended to improve speech, language, communication or swallowing.


In a comparison of treatments, unfair means giving an advantage to one treatment over another.

Word finding difficulties

Occurs when a person knows what word they want to use but has difficulty in retrieving it and using it in their speech. This sometimes happens after having a stroke.