“Advance directives, including a living will and durable power of attorney for health care, are used so that the desires of the individual will be followed in the event he or she lacks the capacity to participate in health care decisions. This ability refers to decision-making capacity.
The standards for decision-making capacity vary from state to state but generally include four abilities: patients must (1) have the ability to understand the relevant information about proposed diagnostic tests or treatment, (2) appreciate their situation (including their values and current medical situation), (3) use reason to make a decision, and (4) communicate their choice. A patient’s capacity is both temporal and situational and capacity evaluations should occur in the context of the specific health care decision that needs to be made. Some patients lack capacity for specific periods of time, such as when critically ill, but not permanently. Although some people are completely incapacitated, many have limited capacity. Those with limited capacity may be able to make some diagnostic and treatment decisions (generally less risky decisions) but not others. Physicians commonly hold patients to higher standards when judging capacity for more serious medical decisions. There is a relationship between capacity and cognition but a patient with dementia can still have decision-making capacity. With Mini-Mental State Examination scores <20 (maximum score = 30) there is an increased likelihood of incapacity, but this varies from case to case and is situation dependent.
Competence is a legal term and is a judicial decision made by a court. Any licensed physician can make a determination of capacity, and a psychiatrist is not required.” ABFM
References
Prim Care Companion J Clin Psychiatry. 1999 Oct; 1(5): 131–141. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC181079/
JAMA. 2011 Jul 27;306(4):420-7. https://www.ncbi.nlm.nih.gov/pubmed/21791691
Am Fam Physician. 2012 Mar 1;85(5):461-466.
http://www.aafp.org/about/policies/all/planning-care.html (Last accessed 2017)