Many individuals who lack capacity to make decisions may still be able to express their wishes in a meaningful way, even if such expression may not fulfil all of the requirements for consent. Prospective participants may be capable of verbally or physically assenting to, or dissenting from, participation in research.
Those who may be capable of assent or dissent include:
those whose capacity is in the process of development, such as children whose capacity for judgment and self-direction is maturing;
those who once were capable of making an autonomous decision regarding consent but whose capacity is diminishing or fluctuating; and
those whose capacity remains only partially developed, such as those living with permanent cognitive impairment.
Where an authorized third party has consented on behalf of an individual who lacks legal capacity, but that person has some ability to understand the significance of the research, the researcher shall ascertain the wishes of that individual with respect to participation. While their assent would not be sufficient to permit them to participate in the absence of consent by an authorized third party, their expression of dissent or signs suggesting they do not wish to participate must be respected. Prospective participants’ dissent will preclude their participation (TCPS 2, Article 3.10).
Where individuals have signed a research directive indicating their preferences about future participation in research in the event that they lose capacity or upon death, researchers and authorized third parties should be guided by these directives during the consent process.
Researchers should be aware of all applicable legal and regulatory requirements with respect to capacity. These may vary among jurisdictions. Authorized third parties who are asked to make a consent decision on behalf of a prospective participant should also be aware of their legal responsibilities.
The consent process must comply with the requirements of the TCPS (2), Section 3 – The Consent Process, and where appropriate, with the ICH Good Clinical Practice: Consolidated Guidelines, Section 4.8, Informed Consent of Trial Subjects.
For further information see the Tri-council Policy Statement: Ethical Conduct for Research Involving Humans (2010)