Capacity to Consent to Treatment

The capacity to consent to treatment, also known as treatment consent capacity (TCC) and medical decisionmaking capacity, is a civil legal capacity with important ethical, legal, and functional aspects. TCC is a fundamental aspect of personal autonomy and self-determination and refers to a person’s cognitive and emotional capacity to consent to medical treatment. TCC involves the capacity not only to accept a treatment but also to refuse a treatment, or to select between treatment alternatives. Legally, TCC forms the cornerstone of the medical-legal doctrine of informed consent, which requires that a valid consent to treatment be not only informed and voluntary but also competent. Functionally, TCC may be viewed as an “advanced activity of daily life” that is an important aspect of health and independent living skills in both younger and older adults. As such, it is a critical functional and life skill considered by probate courts conducting guardianship determinations.

From a legal standpoint, TCC is a distinctive civil capacity. Issues of TCC generally arise in a medical setting and usually involve a physician, a psychologist, or some other clinician, not a legal professional, as decision maker. These clinical judgments of TCC are rarely subject to judicial review. Accordingly, while clinicians do not determine TCC in a formal legal sense, their decisions often have the same effect insofar as a patient can effectively lose decisional authority.

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Over the past 30 years, consent capacity has emerged as a distinct field of legal, ethical, clinical, and behavioral research. Clinical and cognitive models of TCC, and associated assessment instruments, have been developed for evaluating TCC. TCC is often tested using four standards drawn from case law and the psychiatric literature: the capacities to

  1. “evidence” or express a treatment choice (expressing choice),
  2. “appreciate” the personal consequences of a treatment choice (appreciation),
  3. “reason” about treatment (reasoning), and
  4. “understand” the treatment situation and choices (understanding).

There is also a fifth consent ability of making a “reasonable” treatment choice (reasonable choice), which is used experimentally but not clinically. These consent abilities represent different legal thresholds for evaluating TCC and have served as the conceptual basis for instrument development and clinical and cognitive studies.

Legal Aspects of TCC

TCC is a fundamental aspect of personal autonomy in our society. Clinicians are ethically and legally obligated to respect patients’ right of self-determination with respect to medical care. The doctrine of informed consent protects this right of self-determination by requiring that a legally valid consent to treatment be informed, voluntary, and competent. As such, a diagnostic or therapeutic intervention that is performed on a person lacking the capacity to consent—regardless of its intended benefit—may often represent a technical battery and be actionable under the law.

Medical-Legal Model of Consent Capacity

As discussed above, a medical-legal model of TCC incorporating specific consent abilities, or standards, has been developed from case law and the psychiatric literature. These standards are set forth below in order of proposed difficulty for patients with dementia:

S1. The capacity simply to “evidence” or express a treatment choice

S2. The capacity to make a “reasonable” treatment choice (this is not a clinically accepted consent standard because of concerns about the arbitrariness of the operative term reasonable; it is thus for experimental use only and is accordingly referenced with brackets)

S3. The capacity to “appreciate” the personal consequences of a treatment choice

S4. The capacity to reason about treatment and provide “rational reasons” for a treatment choice

S5. The capacity to “understand” the treatment situation and treatment choices

The above standards represent different thresholds for evaluating TCC. For example, S1 (expressing choice) requires nothing more than the subject’s communication of a treatment choice. [S2] (reasonable choice) calls for the individual to demonstrate a reasonable treatment choice, particularly when the alternative is unreasonable. S3 (appreciation) requires the individual to appreciate how a treatment choice will affect him or her personally. S4 (reasoning) evaluates the individual’s capacity to supply rational reasons for the treatment choice. S5 (understanding) is a comprehension standard and requires the individual to demonstrate conceptual and factual knowledge concerning the medical condition, its symptoms, and the treatment choices and their respective risks/benefits. Standards 3 to 5 are the standards generally applied in clinical settings. It should be noted that this medical-legal model can be readily applied to other consent capacities, such as the capacity to consent to research, and to decisional capacity generally.

In using this model and selecting applicable standards, clinicians should consider the potential risks and benefits of a proposed treatment and the consequences of refusing treatment. For instance, a patient who consents to a relatively low-risk medical procedure expected to yield significant benefits may be judged using a lower or more liberal standard of TCC. A more stringent threshold (e.g., S4, reasoning, and/or S5, understanding) should be considered as the risks associated with a medical procedure or with refusing treatment increase. Due to its short-term memory and other cognitive demands, S5 may be the most stringent legal standard, particularly for older adults and persons with amnesic disorders.

Cognitive Model for Consent Capacity

TCC may also be conceptualized cognitively as consisting of three core tasks: comprehension and encoding of treatment information, information processing and internally arriving at a treatment decision, and communication of the treatment decision to a clinical professional. These core cognitive tasks occur in a specific context: a patient’s dialogue with a physician, a psychologist, or some other health care professional about a medical condition and potential treatments. The comprehension/encoding task involves oral and written comprehension, and encoding, of novel and often complex medical information presented verbally to the patient by the treating clinician. The information-processing/decision-making task involves the patient processing the consent and other information presented, integrating this information with established personal knowledge, including values and risk preferences, reasoning about and weighing this information, and arriving internally at a treatment decision. The decision communication task involves the patient communicating his or her treatment decision to the clinician in some understandable form (e.g., oral, written, and/or gestural expression of consent/nonconsent).

Clinical Assessment of TCC

Problems in Assessment

Despite the relevance of issues of TCC in medical settings, there is little academic or clinical education in this area. Medical and graduate schools, as well as residency, internship, and fellowship programs, have not traditionally offered formal training in capacity assessment. There has also been a general lack of practical clinical guidelines on which to base capacity assessments. Until recently, clinicians have had to rely almost exclusively on subjective clinical impressions and brief mental status testing in reaching a judgment regarding TCC.

Physician judgment has traditionally represented the accepted criterion or gold standard for determining TCC in medical and legal practice. However, studies involving older adults and persons with AD have raised the concern that physician judgments of TCC may be both subjective and unreliable. Specifically, experienced physicians have been found to be highly inconsistent in their judgments of TCC in older adults with mild AD. This inconsistency may reflect issues of lack of clinical training, differing conceptual approaches, and the conflation of mental status results with capacity status in older adults. One response to these issues of clinical accuracy and consistency in capacity judgments has been the development of standardized assessment measures.

Instruments for Assessing TCC

In recent years, investigators have used the above models of TCC to develop standardized, norm-referenced psychometric instruments for assessment of TCC in different patient populations. These instruments include the MacArthur Competence Assessment Tool for Treatment (MacCAT-T), the Hopemont Capacity Assessment Instrument, and the Capacity to Consent to Treatment Instrument (CCTI). These standardized measures assist clinicians by offering specific definitions of the TCC construct and by operationalizing standards or thresholds for testing capacity. In addition to measuring capacity performance, some instruments also identify capacity status (capable, marginally capable, or incapable) using cut scores derived from control performance. Thus, these measures provide objective, norm-referenced information concerning an individual’s TCC that can inform and guide clinical decision making.

The limitations of these assessment instruments should also be considered. First, instrument-based deficits in TCC should not be construed as necessarily reflecting clinical or legal impairments or incompetency. Second, and related, clinical determination of TCC is ultimately a judgment made by a clinician and not an instrument performance score. Assessment instruments can provide objective information about consent abilities but are not substitutes for clinical judgment. No capacity instrument can satisfactorily take into account the myriad medical, legal, ethical, and social considerations that inform a clinical or legal capacity judgment. For this reason, standardized measures of TCC are intended to support, but certainly not replace, the decision making of the clinician.

Research on TCC in Clinical Populations

Impairment and loss of TCC have been studied in multiple clinical populations, including persons with schizophrenia and other psychiatric illnesses, Alzheimer’s disease (AD), mild cognitive impairment (MCI), Parkinson’s disease (PD), and traumatic brain injury (TBI). Initial pioneering clinical studies of TCC were carried out in psychiatric populations by Appelbaum, Roth, Grisso, and colleagues and have documented clearly the effects of mental illness on informed consent capacities in these patients. Over the past 15 years, there have been an increasing number of studies of TCC in older adult populations with dementia. Due to its relentless progressive nature and the well-characterized stages of neurocognitive and functional change, AD has proven to be a useful prism for understanding impairment and loss of TCC. Studies have shown that the minimal standards of consent capacity, such as expressing choice (S1) and making a reasonable choice [S2], are relatively preserved in patients with mild to moderate AD, whereas the clinically relevant standards of appreciation (S3), reasoning (S4), and understanding (S5) already show significant impairment. TCC also shows significant longitudinal decline over a 2-year period in patients with mild AD. A very recent study has suggested that older patients with MCI, the prodrome or transitional stage to AD, also experience significant deficits in TCC. Other studies have identified deficits in TCC in patients with PD and cognitive impairment and dementia. In contrast to these dementia studies, an investigation of TCC in moderate to severely injured patients with TBI found significant initial impairment but also subsequent partial recovery of consent abilities 6 months following TBI. Thus, trajectories of consent capacity impairment and change over time can differ enormously across disease states.

Cognitive Studies of TCC

TCC assessment instruments have also provided a useful psychometric criterion for investigating the neurocognitive changes associated with impairment of TCC in neurocognitive disorders such as dementia. Findings suggest that multiple cognitive functions are associated with the loss of consent capacity in patients with AD. For example, deficits in conceptualization, semantic memory, and probably verbal recall appear to be associated with the significantly impaired capacity of both mild and moderate AD patients to understand a treatment situation and choices (S5). A factor analysis of TCC in an AD population revealed a two-factor solution comprising verbal reasoning and verbal memory, which was subsequently validated using a form of neuropsychological confirmatory analysis. In contrast, in studies of patients with PD and dementia, executive function measures have emerged as the primary predictors of impairments of TCC.


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