Medically unexplained physical symptoms

Medically unexplained physical symptoms (MUPS) or medically unexplained symptoms (MUS) are patient symptoms for which the treating physician, other healthcare providers, and research scientists have found no medical cause. The term does not necessarily imply that a physical cause does not exist, but rather notes that cause(s) for given symptoms are uncertain, unknown or disputed—there is no scientific consensus. A task force of the US National Institutes of Health states, "Medically unexplained syndromes (MUS) present the most common problems in medicine."

Estimates of primary care consultations with medically unexplained symptoms range from 15% to a high of 66% in specialty settings. Psychiatric co-morbidity is common, but symptoms may not be due exclusively to psychiatric factors and there may be a strong association between psychiatric morbidity and physical symptoms irrespective of whether they have a medical explanation or not. Association with depressive and anxiety disorders increases with the number of unexplained symptoms reported, but medically unexplained symptoms "as a whole" are not necessarily associated with depression and anxiety.

Physical symptoms have been associated with adverse psychosocial and functional outcome across different cultures, irrespective of etiology (either explained or unexplained). One use of the term MUS is in reference to the overlapping symptoms present in a variety of conditions such as chronic fatigue syndrome, fibromyalgia, multiple chemical sensitivity, somatoform disorder, and Gulf War Illness, which also share a significant overlap in treatment.

History and usage
MUPS may be synonymous with somatization disorder or psychosomatic illness, where the cause or perception of symptoms is mental in origin, or may overlap these terms or be a "lower threshold variant" of them. Because several definitions of both somatization and MUPS exist, and the usage of both terms is inconsistent in medical literature and practice, MUPS is sometimes used interchangeably with somatization and functional somatic symptoms, although "somatised mental distress" and "somatisation disorders" (based on symptom counts) may not adequately account for most patients seen with MUPS.

A study of terms related to MUPS found that patients often object to the phrase "medically unexplained." The study revealed differences between patients' and doctors' opinions. For example, patients preferred terms using the word "functional" although doctors felt this word was potentially offensive.

When a cause for MUS is found, the symptom(s) are no longer medically unexplained. Some cases of ulcers and dyspepsia were considered MUS until bacterial infections were found to be their cause.

Contested causation
The lack of known etiology in MUPS cases can lead to conflict between patient and health-care provider over the diagnosis and treatment of MUPS. This conflict can occur in the public arena and may involve media controversy, advocacy groups, scientific and political debate and even legal proceedings.

Diagnosis of MUPS is seldom a satisfactory situation for the patient, as many patients feel this implies it is "all in their head." This can lead to an adversarial doctor-patient relationship, which can develop into an iatrogenic neurosis, thus complicating the situation. A 2008 review in the British Medical Journal stated that a doctor must be careful not to tell a patient that nothing is wrong, "as clearly this is not the case." The symptoms that brought the patient to the doctor are real, even when the cause is not known. The doctor should try to explain the symptoms, avoid blaming the patient for them, and work with the patient to develop a symptom management plan.

According to psychiatrist Simon Wessely, "Various names have been given to medically unexplained symptoms. These include somatisation, somatoform disorders and functional somatic symptoms." He writes that "a substantial overlap exists between the individual syndromes and that the similarities between them outweigh the differences." In reply, the psychiatrist Peter White has stated that "the concept of a general functional somatic syndrome is unhelpful in understanding illness, aetiology, treatment and outcome". In another publication, Wessely states that providing a label for a set of symptoms "is not a neutral act, since specific labels are associated with specific beliefs and attitudes," and "even when organic illness is certain, the illness label can result in adverse behaviour changes.", while there is conflicting evidence on whether such labelling is helpful.

Luxenberg et al. write that a substantial portion of MUPS and associated somatoform disorders have a clearly identified cause: repeated psychological traumas, particularly during childhood. Evidence indicates that repeated abuse or other traumas often leads to disturbed lymphatic system functioning, under-production of cortisol and overproduction of endogenous opioids, all of which can contribute to MUPS. Those who were seriously traumatized on three or more occasions during childhood were substantially more likely than a control group to develop such difficult-to-treat MUPS as chronic headaches, pelvic pain, and seizures. Trauma researcher Bessel van der Kolk has noted that chronically abused persons sometimes report a baffling array of MUPS while simultaneously reporting none of the expected psychological distress related to their abuse; he further suggests that, due to severe dissociation, chronic physical symptoms are these people's only means of expressing what would otherwise be overwhelming emotional pain.

Treatment
The most effective current treatment for some medically unexplained symptoms is a combination of therapeutic approaches tailored to the individual patient. Most MUS patients are in need of psychotherapy, relaxation therapy and physiotherapy under medical supervision. A combined therapeutic approach which is at least twice as effective as other therapeutic modalities published to date is described in Steele RE et al. "A novel and effective treatment modality for medically unexplained symptoms" The next best documented approach is cognitive behavioral therapy (CBT), with evidence from multiple randomized controlled trials. Antidepressants may also help, but the evidence is "not yet conclusive." The effectiveness of CBT and antidepressants has not been studied for all medically unexplained symptoms, however. Evidence for a positive effect of CBT has been found in trials for fibromyalgia, chronic fatigue syndrome, irritable bowel syndrome, unexplained headaches, unexplained back pain, tinnitus, and non-cardiac chest pain. As of 2006, CBT had not been tested for menopausal syndrome, chronic facial pain, interstitial cystitis, or chronic pelvic pain.

For antidepressants, both tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs) have been tested for some medically unexplained symptoms. TCAs have effects on IBS, fibromyalgia, back pain, headaches, and possibly tinnitus, and single studies show a possible effect in chronic facial pain, non-cardiac chest pain, and interstitial cystitis. SSRIs are usually not effective or have only a weak effect. One exception is menopausal syndrome, where SSRIs are "possibly effective" as well as a third class of antidepressants, the serotonin-norepinephrine reuptake inhibitors (SNRIs).

A randomized controlled trial of multi-faceted, collaborative care found some improvement in the mental health of people with forms of MUS involving somatoform disorders and psychological distress.