Functional neurological disorder (FND) is the current preferred term for what was historically called "conversion disorder" — it encompasses motor symptoms (weakness, tremor, gait disorder, non-epileptic attack disorder / dissociative seizures), sensory symptoms (numbness, vision loss, hearing loss), and autonomic symptoms (syncope, bladder dysfunction) that are not explained by organic neurological disease. Critically, FND is now conceptualised as a disorder of neurological function (how the brain controls the body) rather than a psychiatric condition — there are consistent neuroimaging findings showing altered predictive processing and attention regulation. The diagnosis of FND is positive (based on clinical signs like Hoover's sign for functional leg weakness) rather than purely exclusionary. The risk of attributing early organic neurological disease to FND is real — multiple sclerosis, myasthenia gravis, and functional movement disorders often coexist or are misdiagnosed as each other. The safety principle is: the MUS/FND diagnosis must be reviewed regularly and any new objective clinical findings must be investigated fully, not attributed to the pre-existing functional diagnosis. Fabricated or induced illness (FII) in children (formerly Munchausen by Proxy) is a form of child abuse — the GP's role is to recognise unusual patterns of illness presentation (symptoms only witnessed by one carer, multiple attendances with unexplained symptoms, excessive medical investigation sought, symptom resolution when away from parent) and refer to paediatric safeguarding.

The shift from "medically unexplained symptoms" to "functional symptoms" or "bodily distress disorder" (BDD — ICD-11) reflects an important conceptual change — these are not "unexplained" but rather "functionally explained" by altered central processing, central sensitisation, and the interaction between psychological state and physical symptom generation. Research using fMRI has demonstrated consistent patterns of altered attention, interoception, and predictive processing in patients with functional symptoms. The biopsychosocial model (Engel, 1977) remains the most useful framework: symptoms arise from the interaction of biological predisposition, psychological factors (anxiety, depression, trauma, illness beliefs), and social context (stress, loss, relationship difficulties). The risk of excessive investigation in MUS is not theoretical — each investigation that comes back "normal" is experienced by the patient as "the doctor doesn't believe me" or "they still haven't found what's wrong," reinforcing the search behaviour. Studies show that reassurance following normal test results in MUS patients reduces anxiety for only hours to days before it returns to baseline. The RCGP curriculum (and SCA examinations) specifically tests whether GP trainees can have a direct, empathetic, and confident conversation about functional symptoms — neither dismissing the symptoms nor over-medicalising them.

The 3 Ps model of functional symptoms (Predisposing + Precipitating + Perpetuating) provides a highly practical clinical framework that patients can understand and engage with. Presenting this model to the patient ("I'd like to understand what may have set the stage for your symptoms, what triggered them, and what might be keeping them going") validates the complexity of their experience and opens a collaborative conversation. The perpetuating factors are the most amenable to intervention — fear-avoidance behaviour (avoiding activity because it makes symptoms worse) perpetuates deconditioning in CFS/ME and fibromyalgia; illness-reinforcing medical investigation perpetuates health anxiety; catastrophising perpetuates chronic pain. Addressing perpetuating factors is the key mechanism by which CBT improves functional symptoms. The ACE questionnaire is available free on the NHS website and takes 5 minutes to complete. Scores of 4+ ACEs are associated with dramatically increased risk of physical and mental health problems including MUS. However, administering the ACE questionnaire requires clinical judgement — it should not be given to a patient who is not yet ready to discuss trauma, and it should always be accompanied by a plan for what to do with the information (psychological referral, trauma-focused therapy, safeguarding if relevant).

Hoover's sign for functional leg weakness takes 60 seconds and is highly specific (90%) for functional (non-organic) lower limb weakness — it exploits the automatic synergistic motor patterns that occur with voluntary movement. Method: patient supine, examiner places hand under both heels. Ask patient to lift the weak leg — in organic weakness, the normal leg presses firmly down (automatic synergy). In functional weakness, there is no downward pressure from the normal leg during attempted lift of the weak leg. THEN ask patient to lift the normal leg — in functional weakness, there will be involuntary downward pressure from the "weak" leg (the automatic synergy works from the other direction). This disparity between voluntary and involuntary motor output is the hallmark of FND. The principle that communicating "normal investigations" simply as "nothing's wrong" is counterproductive cannot be overstated — for a patient who has been suffering real symptoms, "nothing wrong" is dismissive and damaging to the therapeutic relationship. The evidence-based communication approach is: "Your tests don't show damage or disease in the organs we tested — but that's actually reassuring. It means the problem is in how your nervous system/gut/muscles are functioning, not in the structure itself. This is very common and it's very treatable — let me explain how it works."

NICE NG206 (Myalgic Encephalomyelitis/Chronic Fatigue Syndrome, 2021) was a landmark guideline change — it removed graded exercise therapy (GET) and cognitive behaviour therapy (CBT) as the primary recommended treatments for CFS/ME, replacing them with a personalised, patient-led approach centred on energy management, pacing, and symptom management. The removal of GET reflects the understanding that pushing through fatigue ("boom-bust" cycles) worsens CFS/ME in many patients (post-exertional malaise). CBT is still available as a supportive intervention for managing the psychological impact of CFS/ME, but not as a primary treatment aimed at "changing beliefs about exercise." This was a significant and sometimes controversial guideline change. GPs should be aware of the current NICE NG206 recommendations and avoid referring CFS/ME patients for graded exercise therapy — this is now explicitly not recommended. The ME Association and MEAction patient advocacy groups are useful resources for GPs to understand the current evidence base and patient experience.

Pain Neurophysiology Education (PNE) is an evidence-based approach to explaining chronic pain and functional symptoms — it teaches patients the neuroscience of how central sensitisation occurs, why the brain produces pain signals in the absence of tissue damage, and how cognitions and beliefs about pain modulate the experience. Multiple RCTs have demonstrated that PNE reduces pain intensity, disability, and catastrophising in chronic pain and fibromyalgia — effect sizes comparable to CBT. The PNE approach reframes pain from "evidence of damage" to "overprotective nervous system response" — this cognitive shift (from "damage" to "dysfunction") reduces fear-avoidance behaviour and enables graded rehabilitation. The therapeutic alliance (the quality of the doctor-patient relationship) is the strongest predictor of outcome in MUS — above any specific treatment modality. Patients who feel heard, validated, and respected by their GP engage better with psychological referrals, exercise programmes, and self-management strategies. Patients who feel dismissed, disbelieved, or accused of fabrication disengage from all treatment, escalate investigations, and develop treatment-resistant illness. The GP consultation IS the treatment for MUS — the explanation, the validation, the co-produced plan, and the committed ongoing relationship are all therapeutic in themselves.

Low-dose amitriptyline for IBS (10 mg nocte — a dose far below the antidepressant threshold of 75–150 mg) works through a different mechanism than its antidepressant action — at low doses, it reduces visceral hypersensitivity by blocking sodium channels in the gut enteric nervous system, and modulates ascending pain signals through descending serotonin and noradrenaline pathways. Multiple RCTs (including the ATLANTIS trial, Lancet 2023) have confirmed that low-dose amitriptyline significantly reduces IBS symptom severity compared to placebo — NNT approximately 5 for clinically meaningful response. This is one of the most evidence-based pharmacological treatments in IBS. The Low-FODMAP (Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols) diet reduces IBS symptoms in 70% of patients with IBS-D and IBS-M — it is one of the most effective dietary interventions in medicine. However, it must be supervised by a dietitian because it is a complex elimination and reintroduction protocol, and long-term restriction of all FODMAP foods is nutritionally harmful. GP referral to a dietitian for IBS-FODMAP guidance is an underused but highly effective intervention.

Mindfulness-based stress reduction (MBSR) for functional symptoms is supported by multiple high-quality RCTs — a Cochrane review of MBSR for chronic pain found moderate evidence for reduced pain intensity, reduced depression, and improved quality of life. The mechanism is the development of non-judgmental awareness of bodily sensations — patients learn to observe symptoms without catastrophising, which reduces the emotional amplification of pain. The 8-week standard MBSR programme (1 session/week × 8 weeks + home practice) is available through IAPT and private mindfulness services. MBSR is one of the most cost-effective MUS interventions — the benefits persist for 12+ months post-course. The NeuroSymptoms.org website (developed by Dr Jon Stone, the UK's leading FND neurologist) is the most reliable, accessible, evidence-based patient information resource for functional neurological symptoms — it has been validated in patient surveys and contains video demonstrations of positive FND signs, explanation of the mechanism, and a self-management programme. GP endorsement of this resource at the time of FND explanation significantly improves patient understanding and engagement.

The evidence that scheduled, proactive regular appointments reduce overall GP attendance in MUS patients (Rosendal et al., systematic review) is counterintuitive but robust — by having a predictable regular contact point, patients do not need to develop or amplify symptoms to "earn" a consultation. The crisis-driven appointment pattern (only seeing the GP when symptoms are bad) reinforces the link between symptom severity and medical attention, which positively reinforces symptom amplification. Regular scheduled appointments decouple symptom severity from medical access. Measuring functional outcomes (can the patient walk to the shops? return to work? engage in social activities?) rather than symptom severity is both more clinically meaningful and more useful for tracking treatment response in MUS — symptoms may never fully resolve, but function can improve dramatically. The goal of MUS management is not symptom-free but functionally well. Using the Patient Global Impression of Change (PGIC) scale or the Roland Morris Disability Questionnaire as functional outcome measures at 3-month reviews provides objective data for treatment decisions.