Decisional capacity — factors affecting it and how to assess it

Source: Essentials of Clinical Geriatrics, 7th ed., Ch. 17 (Competence and Informed Consent; four elements of decisional capacity) and Ch. 6 (Delirium and Dementia — mental status examination, executive function, reversible causes, Table 6-5 drugs causing cognitive impairment); Pathy’s 6th ed. — Confusion Assessment Method.

A. Definition and Governing Principles

B. Factors Affecting Decisional Capacity

C. How to Assess Decisional Capacity — Seven Steps

D. Current Practice Update

Textbook position

Current position, 2023–2026

(Essentials 7e / Pathy’s 6e)

Four elements of capacity Formalised as the Appelbaum–Grisso four-abilities model, now the international standard and the described narratively basis for the MacCAT-T and MacCAT-CR “No cognitive screening test is Unchanged and reinforced — the Mini-Cog (recall + clock drawing) is the preferred bedside screen for appropriate”; executive tests who needs fuller assessment beat the MMSE Capacity instruments described 23 instruments now catalogued, with considerable heterogeneity in criteria and operationalisation; as “difficult for older adults” MacCAT-T remains the reference standard, ACE the practical bedside choice Four-abilities model presented Recent commentary documents substantial inter-rater variability, poorer performance in MCI, as settled demonstrated racial bias, and neglect of emotion and values — the call is for safeguards and flexibility, not abandonment Capacity framed as a binary Shift towards supported decision-making under UNCRPD Article 12, India’s RPWD Act 2016 and clinician determination MHCA 2017 — support first, substitute only as a last resort Surrogate arrangements India: MHCA 2017 Section 4 codifies a three-limb capacity test with a presumption of capacity and a described through US nominated representative; for general medical decisions there is still no statutory surrogate guardianship and proxy hierarchy outside the advance medical directive route statutes Capacity assessed as a one-off Emphasis now on serial reassessment, because delirium persists in a substantial minority and capacity event is dynamic Latest Updates (2023–Present)

Indian statutory framework

Mental Healthcare Act, 2017, Section 4 is the only Indian statute that defines capacity. Its three limbs are: ability to understand information relevant to the decision; ability to appreciate any reasonably foreseeable consequence of a decision or of the lack of a decision; and ability to communicate the decision by speech, expression, gesture or any other means. The Act begins from a presumption of capacity, endorses supported decision-making, and restricts the nominated representative to those found to lack capacity.

Indian Journal of Psychiatry commentary highlights a drafting problem: the statute joins the three limbs with “or” rather than “and”, which literally read would allow a person satisfying only one limb to be deemed capacitous. Commentators and clinical practice hold that all three must be satisfied; there have been repeated calls for an amendment and a Code of Practice for capacity assessment.

For general medical (non-psychiatric) decisions, the operative rules remain the capacity limb of “real consent” in Samira Kohli (2008) and the advance medical directive framework under Common Cause (2018, modified 2023) and Harish Rana (2026).

Evidence on the assessment model itself

Journal of the American Academy of Psychiatry and the Law, 2024: the four-skills model shows considerable variability between evaluators, especially pronounced in mild cognitive impairment due to Alzheimer’s disease, and has shown high levels of racial bias. The authors argue the model is often applied too inflexibly and to situations for which it was not designed, and stress that in many circumstances loss of capacity is temporary or reversible.

European Psychiatry, 2025 (Kupsch et al., systematic review to March 2024): identified 23 instruments assessing capacity to consent to treatment, with considerable heterogeneity in criteria and operationalisation — a caution against treating any single tool’s cut-off as definitive.

BMC Psychiatry, 2025 (Norwegian stakeholder study): the four-abilities model is the primary basis of capacity assessment in specialist care, but systematic training, validated tools and further research are needed to improve assessment quality in routine practice.

JAGS 2024: scoping review of decision-making tools that support substitute decision-makers — emphasis has shifted from merely declaring incapacity to actively supporting the surrogate.

JAGS 2025: scoping review of shared decision-making interventions for deprescribing in older adults with polypharmacy — consent to stop a drug requires the same capacity assessment as consent to start one.

Epidemiology that drives practice

Meta-analytic data in hospitalised older adults show a delirium prevalence of about 21% and a frailty prevalence of about 34%, with frailty an independent risk factor for delirium (RR 1.66) — a large minority of ward patients have a potentially reversible barrier to capacity at any moment.

Persistent delirium is common: pooled prevalence at discharge around 36%, and modelling suggests roughly 16% at 12 months — capacity must be reassessed serially, not certified once.

Dementia prevalence in older general-hospital inpatients ranges from 13% to 63%, and fewer than one-third of studies screened for delirium or depression — misclassification of reversible impairment as dementia is frequent. Longitudinal MacCAT-T data in mild-to-moderate dementia show that reasoning is the ability that fails first and most often (about 23% impaired at 9 months; about 26% impaired overall), while appreciation and expressing a choice are relatively preserved. Clinically, probe reasoning hardest.

Examiner’s Tip

Skeleton: Capacity (clinical) vs competence (legal) → presumption of capacity → decision-specific, time-specific, sliding scale; an unwise decision is not incapacity → the four abilities with model questions → factors: neurocognitive, delirium, psychiatric, drugs, metabolic, sensory, educational-cultural, decision complexity, environment and assessor bias, fluctuation → assessment: optimise → disclose with teach-back → four-ability interview → screening tests support only (Mini-Cog/Clock/EXIT, not MMSE alone) → MacCAT-T / ACE if contested → re-check consistency → document → second opinion → if incapable: support first, then AD → nominated representative → substituted judgement → best interests, and reassess.

“Capacity is decision-specific, time-specific and risk-proportionate — it is never a global label, and it is judged by the process of reasoning, not by the choice made. The four abilities that must all be present are understanding, appreciation, reasoning and expressing a choice; in dementia, reasoning is the ability that fails first, so it is the one to probe hardest.”

“No cognitive screening test determines capacity — the MMSE least of all. Tests of executive function (Clock Drawing, Mini-Cog, Executive Interview) correlate far better, and the MacCAT-T or the Aid to Capacity Evaluation should be used when the case is contested. But before any of this, the first duty is to remove the reversible barrier — delirium, pain, depression, an anticholinergic, hyponatraemia, faecal impaction, or simply a missing hearing aid — because in geriatric practice most apparent incapacity is treatable, fluctuating and temporary.”

Extra Points to Remember — recurring topic

Mnemonic for the four abilities — “U-A-R-C”: Understanding · Appreciation · Reasoning · Choice. Mnemonic for reversible causes — “DELIRIUM”: Drugs · Electrolytes and endocrine · Lack of drugs (withdrawal) · Infection · Reduced sensory input · Intracranial · Urinary/faecal retention · Myocardial and pulmonary (hypoxia).

The three commonest wrong answers in vivas: (i) “MMSE <24 means no capacity” — false; (ii) “he refused surgery so he lacks capacity” — outcome bias; (iii) “he has dementia so the son will sign” — capacity was never assessed.

Delirium vs dementia in one line: delirium = acute, fluctuating, inattention, altered consciousness; dementia = gradual, progressive, consciousness preserved until late.

Assent vs consent: where the patient lacks capacity, still seek assent — their agreement at their own level — and note dissent, which should carry real weight in the best-interests calculation.

Capacity is also needed for non-medical decisions that a geriatrician is often asked about: testamentary capacity (making a will), financial capacity, capacity to drive, capacity to live alone, and capacity to consent to sexual activity in a care home. Each is assessed separately.