Key Facts

Capacity assessment is a core clinical skill. All clinicians are responsible for assessing capacity for decisions within their scope of practice. It is a legal requirement under the Mental Capacity Act 2005.

Epidemiology

• Approximately 2 million adults in England and Wales may lack capacity for some decisions
• Commonly encountered in: dementia, delirium, brain injury, learning disability, severe mental illness, intoxication
• Capacity assessments are performed daily in hospitals, GP practices, and social care settings

Aetiology

Impairment or disturbance of the mind or brain may be caused by:

• Dementia
• Delirium
• Brain injury (stroke, traumatic)
• Learning disability
• Severe mental illness (psychosis, severe depression)
• Intoxication (alcohol, drugs)
• Loss of consciousness

Pathophysiology

The Mental Capacity Act 2005 does not define capacity in pathological terms but in functional terms — it assesses what a person can do with the information relevant to a specific decision, not their diagnosis.

When to Assess Capacity

• When there is reason to doubt capacity for a specific decision
• Before any medical treatment or intervention
• When a patient refuses treatment
• When a patient is making a decision with significant consequences
• When advance care planning
• When considering discharge destination

Five Principles of the MCA 2005

1. Assume capacity unless established otherwise
2. Support decision-making: take all practicable steps to help the person make their own decision (e.g. timing, location, communication aids, interpreter)
3. Unwise decisions are allowed: a person is not to be treated as lacking capacity merely because they make a decision others consider unwise
4. Best interests: any act done for a person who lacks capacity must be in their best interests
5. Least restrictive option: anything done must be the least restrictive of the person's rights and freedoms

Red Flags

• Clinician assuming lack of capacity based on diagnosis alone (unlawful)
• No documented capacity assessment before proceeding with treatment
• Best interests decision made without consulting relevant people
• Lack of capacity assumed because patient makes an unwise decision
• Restraint used without proper legal framework (DoLS/LPS)

Bedside

• Stage 1: Is there an impairment of, or disturbance in, the functioning of the mind or brain? (e.g. dementia, delirium, brain injury, intoxication)
• Stage 2 (if yes to Stage 1): Can the person:
  1. Understand the information relevant to the decision? (presented in simple terms, including risks and benefits)
  2. Retain the information long enough to make the decision? (even briefly is sufficient)
  3. Weigh/use the information as part of the decision-making process? (balance pros and cons)
  4. Communicate the decision? (by any means — speech, writing, signing, blinking)
• Failure in any one of these four = lacks capacity for that decision

Bloods

• May be needed to identify/treat reversible causes of impaired capacity (e.g. delirium workup)

Imaging

• Not required for capacity assessment itself
• May be relevant if investigating underlying cause

Special Tests

• Cognitive assessment (AMT, MoCA, ACE-III) may inform but does not replace formal capacity assessment
• Neuropsychological assessment: for complex cases

Non-pharmacological

• If person HAS capacity: respect their decision, even if it seems unwise; document assessment
• If person LACKS capacity: make a best interests decision (Section 4 MCA)

Best Interests Decision (Section 4 MCA)

• Consider all relevant circumstances
• Consider whether the person will regain capacity
• Involve the person as much as possible
• Consider past and present wishes, feelings, beliefs, and values
• Consult: carers, family, LPA, IMCA (if unbefriended)
• Choose the least restrictive option
• Document the decision-making process

Deprivation of Liberty Safeguards (DoLS) / Liberty Protection Safeguards (LPS)

• If a person lacks capacity and is deprived of their liberty (e.g. kept in hospital/care home), DoLS/LPS authorisation is required
• Six qualifying requirements: age (≥18), mental disorder, lack of capacity, best interests, eligibility, no refusals

Pharmacological

• Not applicable to capacity assessment itself
• Treat reversible causes of impaired capacity (e.g. treat delirium, correct metabolic disturbance)

Surgical/Interventional

• Not applicable

Referral Criteria

• Complex capacity assessments: psychiatry or neuropsychology
• Disputed capacity: seek second opinion, consider Court of Protection
• Serious medical treatment for unbefriended patient: instruct IMCA
• Potential DoLS: supervisory body (local authority)

• Capacity may fluctuate: reassess when there is reason to believe it may have changed
• Capacity may be regained: e.g. after delirium resolves, intoxication clears, depression treated
• Timely capacity assessment ensures patients' rights are protected
• Failure to assess capacity appropriately may have legal consequences
• Good documentation protects patients and clinicians

Mental Capacity Act 2005 — Two-Stage Test

Best Interests Checklist (Section 4 MCA)