Somatic symptom and related disorders

• Somatic symptom and related disorders are conditions in which a person has genuinely experienced, distressing physical symptoms and/or an intense fear of serious illness, with psychological and behavioural features that drive suffering and disability beyond what disease alone would predict.
• Somatic symptom disorder often overlaps with real chronic disease; conversion (functional neurological) disorder is diagnosed by positive (rule-in) signs rather than by excluding every organic cause.
• Illness anxiety disorder is defined by fear of serious disease with absent or only mild physical symptoms, but research suggests the separation between the two health-anxiety diagnoses is mainly one of severity rather than of kind.
• Management centres on validation and explanation, reducing iatrogenic harm, stepwise psychological treatment, rehabilitation for functional neurological symptoms, and careful use of antidepressants for depression and anxiety.
• Prognosis improves with early, clear diagnosis and coordinated care; delays worsen disability, distress and health-care use.

By the end of this page you should be able to:

1. State the DSM-5-TR grouping of somatic symptom and related disorders and how somatic symptom disorder, illness anxiety disorder and conversion disorder differ by definition.
2. Explain why the "medically unexplained" concept is no longer used and how positive criteria (worries, behaviours, examination signs) allow diagnosis without first ruling out all disease.
3. Take a focused history and elicit the examination signs that separate functional from organic weakness, tremor, dystonia, gait disorder and non-epileptic events.
4. Choose and interpret the screening questionnaires in a Table, including PHQ-15 and SSD-12 cut-offs.
5. Outline management aligned with current guidance: validation and explanation, stepped care, psychological therapy, active rehabilitation and multidisciplinary care.
6. Recognise complications, prognosis and the specific needs of children, older adults and pregnant patients.

Two DSM-5-TR changes matter most for practice. First, the older concept of "medically unexplained" symptoms has been abandoned, because somatic symptom disorder can exist alongside physical disease and because unexplained symptoms are neither necessary nor reassuring. Second, "psychogenic" has been replaced by "functional": conversion disorder is diagnosed by positive (inclusion) signs rather than by exhausting every test. ICD-11 uses the related diagnosis of bodily distress disorder.

Distressing physical symptoms are among the commonest experiences in medicine. In a pan-European review of persistent physical symptoms, up to 80 per cent of adults report common symptoms such as pain, fatigue and gastrointestinal upset, and these symptoms account for 30 to 60 per cent of family doctors' workload; symptoms become persistent in 16 to 25 per cent of cases. Physical and mental symptoms commonly coexist. ^[1]

Persistent physical symptoms affect all ages. In children and adolescents pain-related symptoms such as chronic abdominal pain, headache or migraine are reported in about one quarter. In older adults chronic pain affects 25 to 50 per cent of those living in the community and up to 80 per cent of those in nursing homes, with fatigue in 10 to 30 per cent and sleep problems in 40 to 70 per cent. Functional disorders across Europe have an estimated point prevalence of about 8 per cent in adults, with wide variation between conditions and countries. ^[1]

Functional neurological disorder is one of the most common conditions in neurological practice and is diagnosed on the basis of positive signs on examination. Its incidence is estimated at 4 to 12 per 100,000 people per year (4 to 5 per 100,000 for motor presentations and 1.5 to 4.9 per 100,000 for video-EEG-confirmed cases of non-epileptic seizures). Community-registry prevalence is 50 per 100,000. In a well-designed consecutive series of 3,781 outpatients at neurology clinics, 5.4 per cent had a primary diagnosis of functional neurological disorder and 30 per cent had symptoms that were only somewhat or not at all explained by organic disease. Women are estimated to account for 60 to 75 per cent of patients, although functional myoclonus and functional parkinsonism are exceptions that occur at least as often in men. Functional neurological disorder is diagnosed in approximately 16 per cent of outpatient neurology consultations, and functional seizures in approximately 25 per cent of epilepsy monitoring unit admissions. ^[2][5]

There is no single cause. Predisposing biological, psychological and social factors interact with triggering events and with the cognitive and behavioural processes that maintain symptoms over time.

• Biomedical and illness factors. Prior disease, injury, infection, inflammation and residual symptoms that remain after the original cause has resolved can act as triggers and maintaining factors.
• Psychological factors. Adverse childhood or life experiences, neuroticism, illness anxiety, catastrophising, selective attention to bodily cues, alexithymia, avoidance and repeated medical consultations all increase and maintain symptom burden.
• Social and environmental factors. Low socioeconomic status, female sex, stressful encounters with health professionals and employers, and community prejudice about persistent physical symptoms.
• Neurobiological factors. In functional neurological disorder, attention is dysregulated: strong ideas and expectations about sensations correlate with abnormal predictions of sensory data and abnormal body-focused attention. Hypoactivation of the supplementary motor area and relative disconnection with areas that select or inhibit movement, together with increased limbic activation, provide a neurobiological substrate that is separate from feigning or malingering.

Risk factors for functional neurological disorder include recent and historical trauma, medical illness, physical trauma and physiological or psychophysiological events. Precipitating stressors are more common in people with functional neurological disorder than in healthy or clinical controls, but they are not required for the diagnosis.

Persistent physical symptoms arise through the interaction between bottom-up signals from the body and top-down predictions made by the brain from prior experience and expectation. As symptoms continue, their relationship to clearly identifiable tissue pathology often weakens: symptoms may be shaped by expectations, context and bodily attention, not only by disease.

In functional neurological disorder the mechanism is best seen as a disorder of functional brain networks rather than structural damage. Movement is prepared normally, but execution is altered by excessive attention and abnormal body-focused predictions; this is why symptoms improve with distraction and why patients lose the normal sense of agency for the affected movement. Psychological mechanisms can predispose, precipitate and perpetuate the disorder, but a single stressful event is neither necessary nor sufficient. ^[2]

People report one or more distressing physical symptoms, such as pain, fatigue, gastrointestinal or neurological complaints, that are accompanied by excessive thinking about their seriousness, high anxiety about health or symptoms, or excessive time and energy devoted to these concerns. The symptom focus lasts at least six months, although individual symptoms may come and go. In DSM-5-TR the physiology of the symptom need not be "unexplained"; severe symptoms may coexist with, for example, inflammatory bowel disease or multiple sclerosis. Health anxiety is not required, although it is common.

The central feature is preoccupation with having or developing a serious illness. Physical symptoms are absent or mild, but health anxiety is high and is shown by repeated checking, reassurance-seeking, health-related searching, or by avoiding medical contact. The concern persists for at least six months and is not delusional in intensity or better explained by another disorder. Three illness behaviours are recognised: care-seeking, care-avoidant and fluctuating between the two, with the fluctuating pattern being the commonest pattern observed in community samples. ^[4]

Presentations correspond to recognised areas of neurological function:

• Motor: weakness or paralysis, tremor, dystonia, myoclonus, Parkinsonism-like slowing, abnormal gait or postural sway, dysfluency, foreign-accent syndrome and functional dystonic postures.
• Sensory: anaesthesia or altered sensation, visual field defects such as tubular vision, hearing change and functional (persistent postural-perceptual) dizziness.
• Paroxysmal: non-epileptic, dissociative seizures and episodic neurological attacks.

Sudden onset, fluctuation in severity, worsening with attention and improvement with distraction are common but are not by themselves diagnostic. Non-epileptic seizures often last longer than three minutes, with side-to-side head movement, asynchronous limb movements, ictal crying or rapid reorientation. ^[2]

Diagnosis rests on positive signs that are specific for functional neurological disorder; they permit diagnosis without waiting for every test to be normal. ^[2] Some of the most useful signs are:

For weakness specifically, look for variability in severity between assessments performed during a single examination, giveway weakness, and preservation of actions that the examination did not test, such as removing objects from a bag. In functional parkinsonism there is excessive slowness without decrement, variable resistance and normal speed for spontaneous movements.

The principal task is to distinguish somatic symptom and functional presentations from organic disease, and then from psychiatric conditions that also present with physical or health complaints.

No single test diagnoses somatic symptom or conversion disorders. Investigations should be directed by clinical reasoning and should stop once serious organic disease is reasonably excluded, because repeating tests adds harm.

Physical and neurological examination remains the central investigation. For conversion disorder the diagnosis is clinical on positive signs, with neurophysiological or EEG support for functional tremor, myoclonus or non-epileptic seizures when available.

Screening questionnaires help quantify symptom burden and health anxiety and can be tracked over time.

Psychiatry practitioner: Diagnostic criteria are paraphrased and summarised. DSM-5-TR and ICD-11 wording is copyrighted and is not reproduced verbatim here; refer to the original manuals.

• Criterion A. One or more somatic symptoms that are distressing or disrupt daily life.
• Criterion B. Excessive thoughts, feelings or behaviours related to the symptoms, shown by at least one of: disproportionate and persistent thoughts; persistently high anxiety; or excessive time and energy devoted to symptoms or health concerns.
• Criterion C. The state of being symptomatic is persistent, generally at least six months, although individual symptoms need not be present the whole time.
• The symptoms may or may not be fully explained by physical disease; comorbid medical conditions are permitted.

• Preoccupation with having or acquiring a serious illness.
• Somatic symptoms absent or mild only, with disproportionate worry.
• High anxiety about health and excessive health-related behaviours or maladaptive avoidance.
• Duration of at least six months.
• The preoccupation is not delusional and is not better explained by another mental disorder.

• One or more symptoms of altered voluntary motor or sensory function.
• Clinical findings that provide evidence of incompatibility between the symptom and recognised neurological or general medical conditions.
• The symptom is not better explained by another medical or mental disorder.
• The symptom causes clinically significant distress, impairment or warrants medical evaluation.
• Functional neurological disorder can be present alongside neurological disease, provided the symptom itself is not explained by that disease.

Somatic symptom disorder may be specified as mild, moderate or severe depending on the intensity of criterion B features. Conversion disorder may be described by symptom type and, for non-epileptic seizures, by level of diagnostic certainty (possible, probable, clinically established, documented).

Management should be person-centred, comprehensive and, in most cases, stepped: routine explanation and validation, simple self-management and lifestyle advice, then more intensive psychological or pharmacological treatment according to symptom burden and comorbidity. ^[1]

• Identify and treat dangerous or reversible organic disease first.
• Validate the experience: the symptoms are real, common and disabling, and the patient is believed.
• Reduce iatrogenic harm: stop repeating non-contributory tests and invasive treatments, and communicate the diagnosis to every clinician involved.
• Agree a simple plan that both the patient and clinician can follow.

For conversion disorder, explanation is itself a treatment. Success requires that the patient understands that the diagnosis is established and definite rather than a diagnosis of exclusion, that the positive examination findings are demonstrated, and that the disorder is potentially reversible. ^[2] The practical points are:

• name the diagnosis directly
• validate the disability
• do not imply that the patient is deliberately producing symptoms
• allow re-evaluation if new, different symptoms develop (functional overlay and organic comorbidity can coexist)
• avoid discharging the patient without a plan.

• Education and self-management. Individualised, co-constructed explanations that fit the patient's own understanding and culture; modest activity goals; pacing; sleep and nutrition advice.
• Cognitive behavioural therapy. Disorder-adapted CBT is the best-supported psychological treatment for non-epileptic seizures and for a wider range of functional neurological symptoms. Components include education, identifying triggers, challenging unhelpful beliefs, reducing avoidance and broadening to interpersonal functioning.
• Psychodynamic or interpersonal therapy and other therapies. Useful when relationships, emotion or identity conflicts predominate.
• Rehabilitation for functional neurological disorder. Physiotherapy, occupational therapy or speech therapy, focused on relearning normal movement rather than on strengthening weak muscles: weight-shifting and simple movements are established first and complexity is increased; distraction and excessive attention to abnormal movements are avoided. Interventions may include mirrors, video feedback, treadmill training, biofeedback or transcranial magnetic stimulation in selected patients.
• Multidisciplinary care. Severely affected patients may need combined input from neurology, psychiatry, psychology, physiotherapy, occupational therapy and social care.
• For persistent physical symptoms more generally. Staged, collaborative care; mobilising self-efficacy; and, where symptoms persist, specialised inpatient, day-care or rehabilitation programmes that combine medication, psychotherapy, physiotherapy and relaxation. ^[1]

• Antidepressants, usually SSRIs, are indicated for comorbid depression and anxiety and have trial support in functional neurological disorder. In a pilot trial of non-epileptic seizures, 12 sessions of CBT lowered seizure frequency, adding flexible-dose sertraline to CBT produced a similar reduction, and sertraline alone produced a smaller, non-significant reduction. ^[2]
• Tricyclic antidepressants or SNRIs at standard doses may help patients whose persistent physical symptoms include chronic pain, used with the usual cautions.
• Antidepressants may be used for health anxiety associated with somatic symptom or illness anxiety disorder.
• Symptom-directed drugs (anti-tremor medication, for example) are not appropriate for functional symptoms, because the movement is not itself directly treated by such agents.
• Doses. Use standard antidepressant doses and titrate as for depression; refer to your local formulary. The opened guideline sources on this page do not specify doses for somatic symptom or illness anxiety disorders, so individual prescribing must follow the product licence and local guidance.
• Expert reviews of functional neurological disorder support multidisciplinary care, but evidence for medication is limited and individualised. ^[5]

• Suspected or established functional neurological disorder: neurology, and then multidisciplinary FND or neuropsychiatry services where available.
• Significant self-harm risk, severe depression or complex psychiatric comorbidity: psychiatry or clinical psychology.
• Marked functional loss, gait or movement disorder: physiotherapy and occupational therapy.
• Severe family disruption in children: child and adolescent mental health services.

• Iatrogenic harm. Repeated, non-diagnostic investigation and unnecessary surgery or procedures.
• Disability and social exclusion. Loss of work, education and relationships; functional neurological disorder is a common cause of neurological disability.
• Non-epileptic seizures. Injury, status epilepticus mismanagement, driving restriction and social consequence; functional neurological seizure episodes can be prolonged.
• Psychiatric comorbidity. Depression, anxiety, trauma-related conditions and, in severe health anxiety, high service use and cost.
• Chronic pain, fatigue and sleep disturbance maintain disability.
• After stroke-like presentation, delay in correct diagnosis may itself cause distress and repeated attendances.

Collective prognosis is often poor because diagnosis is delayed, poorly delivered or followed by a lack of available knowledgeable therapists. Where the diagnosis is accurate, validated and acted on early, outcomes are better; good outcomes are associated with young age and early diagnosis, whereas long duration before diagnosis, accumulated severe disability and personality disorder predict worse outcomes. Many patients continue to have significant symptoms despite good understanding and acceptance of the diagnosis and despite treatment. Treating comorbid depression, anxiety and pain and limiting iatrogenic harm remain important even in difficult cases. ^[2][1]

Illness anxiety disorder tends to be chronic and episodic, with multiple feared illnesses and onset around early adulthood; long duration of illness anxiety is common.

• Routine screening with short tools such as PHQ-15 and SSD-12 where patients present repeatedly with distressing symptoms, particularly in primary care.
• Early management rather than prolonged investigation: identify risk for persistence (repeated consultations, multiple or increasing symptoms, high perceived distress, impaired functioning), and consider watchful waiting when symptoms are mild and no red flags exist.
• Training clinicians in symptom perception, biopsychosocial explanations and patient-centred communication reduces stigma and improves outcomes.
• Clinical red flags requiring attention: unexplained weight loss, persistent fever, night sweats, unusual bleeding, new lump or mass, difficulty swallowing, jaundice, focal neurological deficit or new severe headache.

Functional neurological disorder can appear or worsen in pregnancy. Any presentation must first exclude pregnancy-specific and neurological causes. Care should be coordinated between general medicine or obstetrics and the relevant mental health clinician; medication choices should follow the product licence and local guidance.

Persistent physical symptoms including pain, fatigue, irritable bowel symptoms and functional neurological symptoms occur in young people. About one quarter of children and adolescents report pain-related symptoms. Rare conversion presentations should be evaluated by neurology and child and adolescent mental health services together. Family involvement and school liaison are often essential, and the prognosis is usually better with prompt, clearly delivered diagnosis. ^[1]

Physical illness burden, sensory loss, bereavement and depression increase the risk of distressing somatic presentations. Somatic symptom disorder may be under-recognised behind explanations of "ageing" or physical disease. Low thresholds for antidepressants and slower titration with attention to falls, anticholinergic burden and hyponatraemia are sensible practice, following the product licence and local formulary.

• A careful history and positive examination signs make the diagnosis possible where imaging and neurophysiology are unavailable.
• Limited investigation should be directed at genuine red flags (focal deficit, fever, weight loss, bleeding, new severe headache).
• Reassurance, validation, explanation and a simple written plan can be delivered by primary-care clinicians.
• Rehabilitation using graded exercise, daily activity goals and avoidance of sick-role behaviour can be provided by nurses and therapists if available.
• Digital psycho-educational resources and remote CBT are becoming useful where specialists are scarce.

• DSM-5-TR removed "medically unexplained" from the somatic symptom and related disorders and defined them by distress, disability and positive psychological features.
• Somatic symptom disorder adds excessive thoughts, feelings or behaviours to one or more physical symptoms and lasts at least six months.
• Illness anxiety disorder centres on fear of serious disease with absent or mild symptoms for at least six months; subtypes include care-seeking, care-avoidant and fluctuating.
• Research suggests IAD and SSD differ mainly in severity rather than in cognitive, behavioural or affective features.
• Conversion disorder is diagnosed by positive (rule-in) neurological signs, not by excluding disease, and does not require a recent identifiable stressor.
• Functional neurological disorder has an estimated incidence of 4 to 12 per 100,000 per year with community-registry prevalence 50 per 100,000; women account for 60 to 75 per cent.
• Misdiagnosis of functional neurological disorder is consistently low (about 4 per cent after a mean of five years' follow-up). ^[2]
• PHQ-15 and SSS-8 measure somatic burden; SSD-12 captures psychological criteria; optimal cut-offs are higher in psychosomatic clinics than in community samples.
• A difference of 3 or more points is a relevant change on both the PHQ-15 and the SSS-8. ^[3]
• Explanation and validation are active treatments, particularly for conversion disorder.
• Functional rehabilitation targets normal movement rather than strength, avoiding excessive attention to abnormal movement.
• Disorder-adapted CBT is the best-supported psychological therapy for non-epileptic seizures and a range of functional symptoms.
• Antidepressants help comorbid depression and anxiety; symptom-directed drugs are inappropriate for functional symptoms.
• Prognosis is better with early, clearly delivered diagnosis and coordinated care.
• Organic disease can coexist with any of these disorders; new, different symptoms should prompt re-evaluation.

Somatic symptom and related disorders connects to anxiety, depression, chronic pain, epilepsy and non-epileptic seizures, neurological examination, persistent physical symptoms in primary care, and rehabilitation for functional conditions.

Somatic symptom and related disorders are common, real and disabling. With a clear, respectful diagnosis, limited but purposeful investigation and coordinated psychological and rehabilitation care, many patients improve.