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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Functional disorder | 1/4 | https://en.wikipedia.org/wiki/Functional_disorder | reference | science, encyclopedia | 2026-05-05T07:29:01.456201+00:00 | kb-cron |
Functional disorders are a group of recognisable medical conditions which are due to changes to the functioning of the systems of the body rather than due to a disease affecting the structure of the body. Functional disorders are common and complex phenomena that pose challenges to medical systems. Traditionally in medicine, the body is thought of as consisting of different organ systems, but it is less well understood how the systems interconnect or communicate. Functional disorders can affect the interplay of several organ systems (for example gastrointestinal, respiratory, musculoskeletal or neurological) leading to multiple and variable symptoms. Less commonly there is a single prominent symptom or organ system affected. Most symptoms that are caused by structural disease can also be caused by a functional disorder. Because of this, individuals often undergo many medical investigations before the diagnosis is clear. Though research is growing to support explanatory models of functional disorders, structural scans such as MRIs, or laboratory investigation such as blood tests do not usually explain the symptoms or the symptom burden. This difficulty in 'seeing' the processes underlying the symptoms of functional disorders has often resulted in these conditions being misunderstood and sometimes stigmatised within medicine and society. Despite being associated with high disability, functional symptoms are not a threat to life, and are considered modifiable with appropriate treatment.
== Definition ==
Functional disorders are a group of conditions characterised by persistent and often distressing symptoms that lead to significant impairment or disability. Unlike structural diseases, where clear abnormalities of organs or tissues can be identified, functional disorders are primarily understood as disturbances in the functioning and communication of body systems. Their pathophysiological basis often reflects dysregulation across neural, autonomic, endocrine, and immune pathways, shaped by interactions between biological, psychological, and social factors.
=== Examples === There are many different functional disorder diagnoses that might be given depending on the symptom or syndrome that is most troublesome. There are many examples of symptoms that individuals may experience; some of these include persistent or recurrent pain, fatigue, weakness, shortness of breath or bowel problems. Single symptoms may be assigned a diagnostic label, such as "functional chest pain", "functional constipation" or "functional seizures". Characteristic collections of symptoms might be described as one of the functional somatic syndromes. A syndrome is a collection of symptoms. Somatic means 'of the body'. Examples of functional somatic syndromes include: irritable bowel syndrome; cyclic vomiting syndrome; some persistent fatigue and chronic pain syndromes, such as fibromyalgia (chronic widespread pain), or chronic pelvic pain; interstitial cystitis; functional neurologic disorder; and multiple chemical sensitivity.
== Overlap == Most medical specialties define their own functional somatic syndrome, and a patient may end up with several of these diagnoses without understanding how they are connected. There is overlap in symptoms between all the functional disorder diagnoses. For example, it is not uncommon to have a diagnosis of irritable bowel syndrome (IBS) and chronic widespread pain/fibromyalgia. All functional disorders share risk factors and factors that contribute to their persistence. Increasingly researchers and clinicians are recognising the relationships between these syndromes.
== Classification == The terminology for functional disorders has been fraught with confusion and controversy, with many different terms used to describe them. Sometimes functional disorders are equated or mistakenly confused with diagnoses like category of "somatoform disorders", "medically unexplained symptoms", "psychogenic symptoms" or "conversion disorders". Many historical terms are now no longer thought of as accurate, and are considered by many to be stigmatising. Psychiatric illnesses have historically also been considered as functional disorders in some classification systems, as they often fulfil the criteria above. Whether a given medical condition is termed a functional disorder depends in part on the state of knowledge. Some diseases, such as epilepsy, were historically categorized as functional disorders but are no longer classified that way.
== Prevalence == Functional disorders can affect individuals of all ages, ethnic groups and socioeconomic backgrounds. In clinical populations, functional disorders are common and have been found to present in around one-third of consultations in both specialist practice and primary care. Chronic courses of disorders are common and are associated with high disability, health-care usage and social costs. Rates differ in the clinical population compared with the general population, and will vary depending on the criteria used to make the diagnosis. For example, irritable bowel syndrome is thought to affect 4.1%, and fibromyalgia 0.2–11.4% of the global population. A recent large study carried out on population samples in Denmark showed the following: In total, 16.3% of adults reported symptoms fulfilling the criteria for at least one Functional Somatic Syndrome, and 16.1% fulfilled criteria for Bodily Distress Syndrome.
== Diagnosis ==