Functional symptom

A functional symptom is a medical symptom in an individual which is very broadly conceived as arising from a problem in nervous system 'functioning' and not due to a structural or pathologically defined disease cause. Functional symptoms are increasingly viewed within a framework in which psychological, physiological and biological factors should be considered to be relevant.

Historically, there has often been fierce debate about whether certain problems are predominantly related to an abnormality of structure (disease) or function (abnormal nervous system functioning), and what are at one stage posited to be functional symptoms are sometimes later reclassified as organic, as investigative techniques improve. Thus, on finding itself unable to discover effective treatments or physiological causes for symptoms, the medical profession, in explaining to itself these limitations of its own power over nature, is of course subject to a temptation to minimize the explanatory role played by the many gaps in its own current scientific understanding, and instead to grope for theories of psychosomatic aetiology to account for the physical symptoms that it cannot otherwise explain, and cannot cure. (To caricature this reasoning: "I can't cure you: you must be mad".) It is well established that psychosomatic symptoms are a real phenomenon, so this potential explanation is often plausible, not always easily refutable, and can be reassuring (at least for the doctor). Sometimes it is correct. For example symptoms associated with migraine, epilepsy, schizophrenia, multiple sclerosis, stomach ulcers, chronic fatigue syndrome, Lyme disease and many other conditions have all tended historically at first to be explained largely as physical manifestations of the sufferer's psychological state of mind; until such time as new physiological knowledge is eventually gained. At this point, a part of the earlier reliance on psychological explanations often evaporates. Taking a long, historical view, doctors being human, there seems little reason to suppose that this historical pattern of eventual correction of earlier psychological misattribution of symptoms is yet become a thing of the past. Another specific example is functional constipation, which may have psychological or psychiatric causes. However, one type of apparently functional constipation, anismus, may have a neurological (physical) basis.

Whilst misdiagnosis of functional symptoms does occur, in neurology, for example, this appears to occur no more frequently than of other neurological or psychiatric syndromes. Although, in order to be quantified, misdiagnosis has to be recognized as such, which can be problematic in such a challenging field as medicine.

A common trend is to see functional symptoms and syndromes such as fibromyalgia, irritable bowel syndrome and functional neurological symptoms such as functional weakness as symptoms in which both biological and psychological factors are relevant, without one necessarily being dominant.