A fundamental flaw with common thinking about decision-making capacity is that it is regarded as a cognitive test, essentially a test of intellectual capacity to make a rational decision.[i] [ii] Too often in the clinical scenario, capacity to consent is determined by whether or not the patient agrees to the proposed intervention. Incapacity is not determined by poor judgement, any specific diagnosis, or a positive score on a screening test for dementia or cognitive impairment. Rather, capacity evaluation is an assessment of the decision-making process, not the actual decision that is made.

The most commonly cited clinical tool and gold standard model of capacity evaluation for consent to treatment is taken from the MacArthur Competence Assessment Tool-Treatment (MacCAT-T), which was developed in 1997 for use in clinical settings.[iii] The key concepts of the MacCAT-T are that the evaluation of decision-making capacity should involve a semi-structured interview that utilizes information (symptoms, diagnosis, and treatment recommendations) to assess:

• ability to understand,
• ability to appreciate,
• ability to reason, and
• ability to express a choice.

Under Ontario’s Health Care Consent Act (HCCA),[iv] a patient has capacity to consent to treatment if they are able to (i) understand the information that is relevant to making the decision and (ii) able to appreciate the reasonably foreseeable consequences of a decision or lack of decision. The legislation in other Canadian provinces are largely similar. The capable patient’s right to refuse treatment and the irrelevance of the patient’s best interests are binding throughout Canada.[v]

The domination of cognitive criteria in formal assessment tools, particularly the MacCAT-T, and the fact that emotional, biographical, and context specific factors are ignored has been criticized.[vi]^, Current approaches that define capacity in cognitive terms disregard concerns that emotional instability may disrupt capacity or that a person may be cognitively intact yet lack the capacity to give a valid consent.[vii] An alternative evaluative approach would be to view capacity holistically, as a combination of biological, psychological, and social (biopsychosocial) factors.

Decision-making capacity can be influenced by emotional instability and cognitive distortions, defined by the American Psychological Association[viii] as “faulty or inaccurate thinking, perception or belief” for which the defining characteristic is often a sense of negativity. That sense of negativity may temporarily disrupt a person’s commitment to their values. For example, applying only a cognitive test of capacity means that a person who has been diagnosed with depression is capable of declining treatment (in the form of cardiac angioplasty) for coronary artery disease. In contrast, a more inclusive, holistic evaluative approach would take into account the biopsychosocial factors motivating the decision to decline treatment.

Granted, the roles of emotions and values in capacity evaluation are complex and a single operational definition may be difficult to determine. However, it has been argued that dysfunction in emotions or valuing could manifest as an impairment in the ability to appreciate the consequences of a decision.[ix]

Clinical guidelines may assist with the assessment of the patient’s capacity, but they do not explicitly address the criteria of the legal test for capacity. As a threshold, the evaluation of decision-making capacity should include an assessment of risk: if the patient is making a decision which involves a risk of death or serious injury, the patient’s capacity should be tested more rigorously and involve a more exacting examination of the evidence to ensure that the legal test has been satisfied. The rigor of the requirement of understanding and appreciating increases with the complexity of relevant information that is required to be understood and appreciated.[x]

The challenge is knowing where to set the standard to determine the threshold for capacity.[xi] Where is the line drawn for an “acceptable” level of understanding and appreciating? How is it determined case by case? The place at which one chooses to draw the line is determined by the policy-oriented goals that one is seeking to attain. In medicine, we call that the standard of care.

My taking a more personalized biopsychosocial approach to capacity evaluation, the standard of care for determining the threshold for capacity for a treatment decision may be more amenable to evaluation, rather than relying on current clinical standards that emphasize a cognitive approach to capacity evaluation, and that are open to bias based on language, education, diagnosis, location, and unreliability amongst clinicians’ methods in determining and documenting capacity.

[i] Margaret Isabel Hall, Mental Capacity in the (Civil) Law: Capacity, Autonomy, and Vulnerability, 2013 58-1 McGill Law Journal 61, 2013, 7.

[ii] Price A, McCormack R, Wiseman T, et al. Concepts of mental capacity for patients requesting assisted suicide: a qualitative analysis of expert evidence presented to the Commission on Assisted Dying. BMC Medical Ethics. 2014;15(32):1–11.

[iii] Grisso T, Appelbaum PS. MacArthur Competence Assessment Tool for Treatment (MacCAT-T). Sarasoto, FL: Professional Resource Press; 1998.

[iv] Health Care Consent Act, SO 1996, c 2 [HCCA].

[v] Sklar, R. (2007). Starson v. Swayze: The Supreme Court speaks out (not all that clearly) on the question of “capacity”. The Canadian Journal of Psychiatry, 52(6), 390-396.

[vi] Eike­Henner W. Kluge (2005). Competence, Capacity, and Informed Consent: Beyond the Cognitive­Competence Model. Canadian Journal on Aging / La Revue canadienne du vieillissement, 24, pp 295­304 doi:10.1353/cja.2005.0077

[vii] Breden, T. M., & Vollmann, J. (2004). The cognitive based approach of capacity assessment in psychiatry: A philosophical critique of the MacCAT-T. Health Care Analysis: HCA, 12(4), 273-83; discussion 265-72. doi:https://doi.org/10.1007/s10728-004-6635-x

[viii] https://dictionary.apa.org/cognitive-distortion

[ix] Kim, S. Y., Kane, N. B., Keene, A. R., & Owen, G. S. (2022). Broad concepts and messy realities: optimising the application of mental capacity criteria. Journal of Medical Ethics, 48(11), 838-844.

[x] Appelbaum, Paul S., MD, Roth, Loren H., MD, MPH. Competency to Consent to Research a Psychiatric Overview Arch Gen Psychiatry 1982;39:951-958).

[xi] Price A. Mental capacity as a safeguard in assisted dying: clarity is needed. Br Med J. 2015:351