Functional Disorder

A functional disorder is a psychological disorder for which no organic cause can be found.

Functional disorder is the general term for any medical condition in which the normal functioning of the body has been impaired even though the body appears to be completely normal under examination by a physician. Conversely, if an impairment of a body part is present and that region appears abnormal, then the general term is structural disorder.

Characterized by multiple symptoms, functional disorders can be associated with any of the body's systems. The overriding feature for any functional disorder is that it does not appear to have any distinct pathophysiological basis. Well-known functional disorders include chronic fatigue syndrome (CFS), chronic pelvic pain (CPP), dyspareunia (painful sexual intercourse), fibromyalgia (widespread musculoskeletal pain), irritable bowel syndrome (IBS), interstitial cystitis (IC, painful bladder syndrome) and dysuria (pain with urination), low back pain, noncardiac chest pain (NCCP, pain in the chest that does not originate from heart conditions), post-traumatic stress disorder (PTSD), and temporomandibular joint pain (TMJ).

The consensus among research scientists and medical physicians is that there exists multiple causes for functional disorders. Many scientists contend that the brain is central to such medical problems. Although not conclusive, researchers have found through scans that the brain reacts to pain differently when a functional disorder is present. Further, patients with functional disorders are not pretending something is wrong. In the past, medical professionals have had difficulties ascertaining the source of their patients’ pain, sometimes concluding that the pain is “all in their heads.” However, physicians know that the pain felt by people with functional disorders is real.

Neuroses versus psychoses

Disorders traditionally classified as neuroses, including a variety of anxiety and mood disorders as well as psychosomatic illnesses, are generally regarded as functional disorders. While conditions classified as psychotic are usually believed to have biological origins, neurotic conditions are generally believed to be caused by developmental, psychosocial, or personality factors. Psychotic disorders not associated with damage to brain tissue from a head injury, infection, or similar causes are also considered functional disorders.

Specific functional disorders

One common grouping of functional disorders is functional gastrointestinal (GI) and motility disorders. The International Foundation for Functional Gastrointestinal Disorders (IFFGD) states that approximately one in four people in the United States have one of these disorders. Further, these GI disorders account for about 40% of all the GI problems that are reported to physicians and related medical professionals.

These functional GI and motility disorders occur when abnormal movements occur within the intestines, when nerves become overly sensitive within the intestines, or when impaired communications occur between the brain and the intestines. In all of these cases, and in others similar in nature, there are no known structural abnormalities within the intestines as seen by various diagnostic tests such as endoscopy and x-ray scans, or by blood tests.

Symptoms of FND are most likely of a neurological nature; however, clear evidence of their origin is unable to be produced. Functional Neurological Disorder Hope, commonly called F.N.D. Hope, is a patient advocacy group for this grouping of functional disorders. F.N.D. Hope states that few effective treatment plans exist for these disorders. The organization has found that the most common treatment used for the disorder is cognitive behavior therapy (CBT), although the success rate is less than 10%.

Uncomfortable diagnoses

Many mental health professionals are uncomfortable with the term functional disorder for various reasons. First, its meaning is often distorted. While the term is essentially a designation of what a disorder is not (i.e., organic), it tends to be interpreted as making positive statements about what the disorder is (i.e., induced by environmental or psychosocial factors) when, in fact, such causes may not have been scientifically proven. In addition, functional as a classification continually is outdated as discoveries are made about the origins of certain disorders. Schizophrenia, for example, would be considered an organic disorder if a biochemical cause for the disease, which some researchers believe exists, could be verified.

By comparison, the current system of classifying disorders in the Diagnostic and Statistical Manual of Mental Disorders: DSM-5, which is organized by the mental faculty or area of behavior that is impaired, is much less likely to become outdated due to new research. A further objection to the term functional disorder is that it implies an artificial separation of the mind and body, as a number of disorders have both organic and functional components.

Of all the functional disorders, certain symptoms appear to be common across the breadth of the grouping. According to the IFFGD, these symptoms include:


A condition in which the muscles or nerves in all or parts of the digestive tract do not function normally with regards to coordination and/or strength.
Also called, physiopathology, the medical discipline that uses both pathology (the study of conditions occurring as a result of a disease) and physiology (the study of processes within an organism).

See also Conversion reaction .



American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders: DSM-5. 5th ed. Washington, DC: Author, 2013.

Ashwell, Ken W. S. The Brain Book: Development, Function, Disorder, Health. Richmond Hill, Ontario, CA: Firefly Books, 2012.

Lacy, Brian E. Functional and Motility Disorders of the Gastrointestinal Tract: A Base Study Approach. New York: Springer, 2015.


Functional Neurological Disorder Hope. “About Functional Neurological Disorder.”, (accessed August 6, 2015).

International Foundation for Functional Gastrointestinal Disorders. “Functional GI Disorders.” (accessed August 6, 2015).

International Foundation for Functional Gastrointestinal Disorders. “IBS and Non-GI Functional Disorders.” (accessed August 6, 2015).

Research Clinic for Functional Disorders and Psychosomatics, Aarhus University Hospital. “Functional Disorders.” (accessed August 6, 2015).


International Foundation for Functional Gastrointestinal Disorders, 700 W. Virginia St., Rm. 201, Milwaukee, WI, 53204, (414) 964-1799, Fax: (414) 964-7176, (888) 964-2001,, .