Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Capacity and compulsory treatment in severe illness
Psychiatry · UK scope · Sources checked 27 Aug 2026 · Clinical review pending
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Refusal with imminent physical danger
A person who is critically malnourished, dehydrated or metabolically unstable and refuses essential assessment, admission or nutrition may deteriorate while clinicians debate capacity or locate a bed; apparent composure does not establish safety or capacity.
Action: Provide immediately necessary emergency care within a defensible lawful basis, obtain senior eating-disorder, medical and mental-health assessment at once, define the exact decision and urgency, and involve the organisation's legal and safeguarding routes early. Arrange the least restrictive safe setting and do not attempt compulsory feeding without a trained multidisciplinary team.
Overview
Assess and document decision-making capacity in severe eating disorders, support autonomous choice, identify when a lawful compulsory framework may be required, and apply the correct nation-specific safeguards to life-preserving treatment.
Severe eating disorders create a difficult interface between autonomy and preservation of life. Capacity is neither guaranteed by articulate speech nor removed by an anorexia diagnosis. The exact statutory test differs across the UK, so the assessment must apply the relevant jurisdiction's incapacity criterion and functional requirements to the particular decision. Someone may decide capably about analgesia but not be able to apply information about nutritional restoration; capacity may also change after glucose, hydration, sleep, infection or acute distress improves.
Support precedes conclusion. Explain information in small, concrete steps, use the person's preferred communication method, offer quiet time, interpreter or advocate, address pain and panic, repeat discussion when feasible and invite them to describe consequences in their own life. Explore whether the person can compare oral meals, supplements and nasogastric feeding, appreciate the risk of no treatment and consider how eating-disorder beliefs influence value assigned to death, weight gain or loss of control. A preselected outcome is not a valid capacity test.
Practice
Two practice questions
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PsychiatryOriginal SBA
Capacity under anorexia
An articulate adult being treated in England for severe anorexia repeats that untreated malnutrition can be fatal but says weight gain is worse than any chance of death. What is the best next step?
Sources and review status8 sources · checked 27 Aug 2026 · clinical review pending+
Sources
Sources and review status
National guidance is shown before implementation-dependent detail. Apply principles in context and verify current guidance when a decision affects care. Source check completed 27 Aug 2026; clinical approval remains outstanding.
GMC decision making and consentUK professional duties for supported, specific and time-sensitive decision-making; updated August 2026.
If an adult lacks capacity, decision-makers must use the framework applicable where care is delivered. England and Wales use the Mental Capacity Act 2005 for many decisions and the Mental Health Act 1983 as amended for compulsory mental-health assessment and treatment. Scotland uses the Adults with Incapacity (Scotland) Act 2000 and the Mental Health (Care and Treatment) (Scotland) Act 2003. Northern Ireland remains in phased implementation of the Mental Capacity Act (Northern Ireland) 2016; the Mental Health (Northern Ireland) Order 1986 and a dual system continue, so local HSC legal advice and current codes are essential.
Capacity law and mental-health law answer different questions. A mental-health statute may provide authority for detention and treatment of the disorder or its manifestations when its criteria and procedures are met; MEED notes that nutrition, including nasogastric feeding, can constitute treatment for anorexia within mental-health legislation. A capacity framework may authorise an overall-benefit or best-interests intervention for a person who lacks capacity, but restraint needs its own statutory conditions and proportionality analysis. The June 2026 UK Supreme Court judgment also changed the separate Article 5 deprivation-of-liberty analysis: a person who lacks legal capacity may nevertheless give valid consent in the Convention sense if their de facto understanding and wishes support it. Compliance alone is insufficient, and this does not supply authority for treatment or force. The team must use current jurisdictional guidance and name the authority for every restrictive act rather than blending statutes loosely.
For children and young people, competence or capacity, parental responsibility, mental-health legislation, children law and court powers can interact differently by age and nation. The young person must be supported and heard even when they cannot legally decide alone. Invasive nutrition over active refusal is especially sensitive: seek a senior multidisciplinary opinion and specialist legal advice early instead of assuming either parental consent or a capacity finding settles every aspect.
Compulsion is a last resort, not a last-minute thought. When a deteriorating patient begins to refuse, clinicians should anticipate thresholds, identify who can perform statutory assessment, discuss the likely treatment plan and locate a safe medical environment with trained mental-health staff. If restriction is used, its purpose, duration and physical risks must be explicit, with debriefing and a plan to reduce or end it.
Key points
Presume an adult has capacity; diagnosis, low weight, unusual values, disagreement or a decision clinicians consider unwise cannot by themselves rebut that presumption.
Capacity is assessed for one clearly defined decision at the time it must be made, after practical support and treatment of reversible barriers to deciding.
The Mental Capacity Act test in England and Wales, and for commenced Mental Capacity Act provisions in Northern Ireland, includes understanding, retaining, using or weighing relevant information and communicating a choice; Scotland's statutory wording differs, and Northern Ireland retains a dual system while commencement is incomplete. Apply the local test rather than exporting one nation's form, while examining carefully how eating-disorder beliefs affect the person's use of information.
Record the proposed intervention, material benefits and burdens, alternatives including no treatment, likely consequences, support offered, the person's own reasoning and how any impairment causes the functional inability.
A capacitous adult's treatment refusal remains valid unless a separate lawful authority applies; a mental-health statute may authorise treatment in defined circumstances even when mental capacity is present.
When capacity is absent, any substitute decision must follow the applicable jurisdiction's benefit or best-interests process, consultation and least-restrictive safeguards; incapacity alone does not authorise detention or force.
Aetiology
01
Starvation-related cognition
Undernutrition, hypoglycaemia, sleep loss and metabolic disturbance can reduce flexibility, concentration and appreciation of immediate personal risk.
02
Disorder-driven valuation
Intense fear, overvaluation of shape or compulsive avoidance can dominate comparison so that nutrition consequences are not meaningfully weighed.
03
Acute comorbidity
Delirium, infection, intoxication, depression, psychosis or neurodevelopmental communication barriers may independently or jointly impair a particular decision.
Pathophysiology
1
Functional impairment
The applicable jurisdiction's incapacity criterion affects the functions required for the defined choice; terminology and any required causal link must be taken from local law.
2
Decision specificity
Different information, stakes and complexity mean capacity can be present for one intervention and absent for another at the same time.
3
Temporal fluctuation
Physiological correction, reduced panic, communication support or progression of illness can change functional ability over hours or days.
4
Restrictive escalation
Active resistance introduces physical and psychological harm from restraint, requiring proportionality and lawful safeguards beyond capacity assessment itself.
Clinical features and red flags
Understanding without appreciation
The person can recite clinical facts but cannot apply the likelihood or seriousness of harm to their own current circumstances.
Disorder-dominated weighing
Fear of weight restoration is acknowledged yet treated as infinitely worse than death, without meaningful comparison of options or consequences.
Fluctuating decision ability
Reasoning deteriorates with hypoglycaemia, delirium, exhaustion or distress and improves after support, treatment or a different time and setting.
Capacitous disagreement
The person understands, retains and genuinely weighs relevant information but reaches a decision clinicians dislike; disagreement alone is not incapacity.
Active resistance
Attempts to remove a tube or physically resist feeding raise separate questions about legal authority, proportionality, staff skill and immediate injury risk.
Child or adolescent refusal
Age, maturity, competence, risk, parental responsibility and nation-specific legislation require individual analysis rather than a single universal consent rule.
Red flags requiring action
Refusal of food, fluid, blood tests, ECG, admission or tube feeding in the context of syncope, awake bradycardia below 40, hypoglycaemia, dangerous electrolytes or organ dysfunction needs urgent joint assessment.
Investigations
01Decision-specific capacity interviewFirst step
Why
Examine the decision-making functions required by the applicable jurisdiction for the exact proposed intervention.
Interpretation and limitations
Document the local statutory elements, functional evidence and required causal link; a diagnostic label or preferred clinical outcome is insufficient.
02Reversible-impairment screen
Why
Assess glucose, hydration, infection, electrolytes, delirium, intoxication, pain, language and sensory barriers.
Interpretation and limitations
Treat immediately dangerous causes and repeat the capacity assessment when improvement is possible without creating unsafe delay.
03Values and advance-wishes review
Why
Identify prior statements, advance decisions where legally applicable, beliefs, relationships and what matters to the person.
Interpretation and limitations
Current and past wishes inform overall-benefit or best-interests reasoning but must be interpreted under the correct jurisdictional rules.
04Legal-authority check
Why
Name the statute, order, certificate, court decision or emergency doctrine relied upon for each restrictive act.
Interpretation and limitations
Detention, treatment, restraint and deprivation of liberty may require different authorities; obtain legal advice when scope is uncertain.
Differential diagnosis
01
Capacitous refusal
A person may understand and genuinely weigh consequences yet choose risk according to values clinicians find difficult or unwise.
02
Communication mismatch
Language, sensory, literacy or autistic communication needs can look like impaired understanding until information and response methods are adapted.
03
Transient delirium
Infection, glucose disturbance, dehydration, medication or substance effects can cause fluctuating attention and reasoning requiring urgent medical treatment.
04
Coerced agreement
Apparent consent obtained through threat, exhaustion or misinformation is not equivalent to a voluntary informed treatment decision.
Management
01Supported capacityDefine, support and evidence the decisionFirst stepA person appears to refuse or hesitate about a treatment necessary to reduce serious eating-disorder harm.+
1Specify the immediate decision, urgency, material risks, reasonable alternatives and consequences of no intervention in accessible language.
2Correct reversible barriers, offer communication support, advocacy and time where safe, then apply the decision-making functions required by the relevant jurisdiction.
3Record the person's own account, statutory and functional evidence, any required causal link, conclusion, review time and how disagreement was separated from incapacity.
02Lawful escalationChoose the jurisdictional routeEscalationSerious risk persists and consent is absent or decision-making ability is impaired.+
1
Complications
01
Preventable physical death
Delayed lawful action during metabolic collapse can allow arrhythmia, hypoglycaemia, organ failure or dehydration to become irreversible.
02
Trauma and injury
Poorly planned restraint can cause aspiration, musculoskeletal injury, circulatory compromise, staff injury and lasting psychological trauma.
03
Rights violation
Using an inapplicable statute or excessive restriction can unlawfully deprive liberty, override autonomy and prevent effective challenge.
04
Therapeutic rupture
Opaque decisions, dismissive language and repeated unnecessary force damage trust and may intensify avoidance after the emergency resolves.
Monitoring and follow-up
Repeat capacity assessment when the decision, clinical state, available options or reversible cognitive factors change; a form is not a permanent status label.
Document the precise legal authority, commencement status where relevant, statutory professionals, review date, advocacy and rights information for any compulsion.
Before and after restrictive feeding, review pulse, circulation, electrolytes, glucose, tube and aspiration risk, restraint injury, psychological distress and refeeding needs.
Record the person's words, wishes, advance statements or decisions, consultation with family or advocates and reasons for accepting or departing from those views.
Hold frequent joint medical and mental-health reviews so legal status, treatment plan and location of care remain aligned with current risk.
Audit each restrictive episode for necessity, proportionality, staff competence, duration, adverse events, debrief and concrete steps towards less restriction.
Special situations
Articulate is not capacitated
Fluent repetition may coexist with an inability to apply risk or weigh it against disorder-driven fear in the actual decision.
Unwise is not incapable
The legal and ethical question concerns the decision process and causal impairment, not whether clinicians endorse the final choice.
Incapacity is not force
A finding of absent capacity begins substitute-decision analysis; it does not itself authorise restraint, detention or deprivation of liberty.
One UK has four systems
Capacity terminology, statutory roles and compulsory-treatment processes differ, so a familiar England-and-Wales form cannot be exported nationwide.
Plan before crisis
Early legal and clinical preparation reduces unsafe delay, improvised restraint and transfers between teams that each assume another holds responsibility.
Rights continue under compulsion
A person receiving treatment without consent still needs information, respect, advocacy, review, the minimum restriction and meaningful participation.
Common pitfalls
01
Declaring incapacity because anorexia is present, BMI is low or the person refuses the intervention clinicians recommend.
02
Accepting a rehearsed description of death risk as proof that the person can use and weigh that risk personally.
03
Writing 'lacks capacity' without defining the decision, functional evidence, causal impairment, support attempted or reassessment plan.
04
Treating the Mental Capacity Act 2005 or Mental Health Act 1983 as if it applies unchanged throughout all four UK nations.
05
Assuming every Mental Health Act 2025 reform is operational before checking commencement and current local statutory guidance.
06
Using family consent, emergency necessity or an incapacity finding as a blanket authority for repeated non-emergency restraint.
07
Attempting nasogastric feeding under restraint on an unprepared general ward without trained mental-health staff and a full medical plan.
Commenced sections 51 and 52 on 6 April 2026, illustrating phased rather than whole-Act implementation.
Law differs across the UK: England and Wales, Scotland and Northern Ireland use distinct capacity and mental-health statutes, terminology, procedures and advocacy roles.
Mental Health Act 2025 changes in England and Wales are being commenced in phases; clinicians must check which provisions are in force rather than assume the whole Act operates.
After the June 2026 UK Supreme Court judgment, lack of domestic-law capacity for care or residence does not automatically answer the separate Article 5 question of valid consent to confinement. Establish the person's actual understanding and wishes under current national guidance; mere compliance is not consent, and the judgment does not authorise unwanted treatment or force.
Feeding without consent is an exceptional treatment requiring an eating-disorder, medical, nursing and legal plan, staff trained for frail patients, and review before every restrictive episode.
A patient may accurately repeat that death is possible yet be unable to use and weigh that consequence because disorder-driven terror of weight restoration dominates the decision.
Fluctuating attention, hypoglycaemia, infection, intoxication, delirium or severe dehydration can additionally impair capacity and may be partially reversible with immediate treatment and support.
Threats, restraint or covert medication without a clearly identified legal authority, trained staff, proportionality and contemporaneous review create serious clinical, ethical and legal risk.
A young person's refusal of invasive life-preserving treatment requires senior paediatric, psychiatric and legal analysis; parental agreement should not be treated as an automatic answer to every competent refusal.
05
Independent multidisciplinary opinion
Why
Combine eating-disorder, physician, dietetic, psychiatric, nursing, safeguarding and advocacy perspectives.
Interpretation and limitations
Consensus strengthens planning but does not replace statutory criteria, the accountable decision-maker or the person's right to challenge.
Confirm whether England or Wales, Scotland or Northern Ireland law applies and obtain advice from the relevant approved or authorised professionals.
2Consider capacity, mental-health, children and court frameworks separately, identify the least restrictive effective option and document why its criteria are met.
3Keep the person involved, consult advocates and those close to them as required, provide challenge and review routes, and reassess as circumstances change.
03Feeding without consentMake every episode exceptional and safeNutrition over active refusal is judged necessary, proportionate and lawfully authorised to prevent grave deterioration.+
1Use a competent multidisciplinary team to agree nutritional prescription, route, restraint risks, medical monitoring, staffing, setting, contingency and criteria to stop.
2Explain what will happen, preserve dignity, use the minimum force and duration, and ensure mental-health staff are trained to support a medically frail person.
3Review authority and proportionality before each episode, record injuries or distress, debrief patient and staff, and pursue a collaborative route away from compulsion.
04Capacitous refusalRespect autonomy while maintaining careA properly supported assessment finds that an adult has capacity for the specific treatment decision and no other lawful authority applies.+
1Respect the refusal, check whether the person wants a second opinion, and agree what assessment, symptom relief or lower-burden option they will accept.
2Explain changing warning signs and emergency routes, maintain contact where possible, and document the material information and the person's reasoning.
3Reassess only if the decision changes, new impairment is suspected or a different decision arises; do not use repeated assessment as coercion.