Informed Consent and Individuals with Diminished Decision-Making Capacity

August 30th, 2017 by Robert Romanchuk, IRB Vice Chair

Researchers continue to chip away at the challenging field of neurological disease, seeking new treatments and potential cures for these conditions. This research is urgently needed: in the US, neurological diseases create nearly $800 billion annually in healthcare costs, and the economic, social and emotional costs of these conditions will continue to grow with our aging population.

When conducting clinical research on neurological diseases, researchers often must provide additional safeguards for the research participants. Conditions like Alzheimer’s Disease, Parkinson’s Disease and others can cause both physical and mental impairment, making individuals vulnerable to coercion or undue influence.

Researchers must be careful to ensure individuals with diminished decision-making capacity (and, if appropriate, their legally authorized representatives) are fully informed about a study and can provide truly informed consent to participate in research.

By “capacity,” I’m referring to a potential research subject’s ability to:

  • Make and express a choice,
  • Understand relevant information,
  • Appreciate the significance of the information relative to the subject’s own situation, and
  • Reason with this relevant information in making decisions.

With this in mind, “diminished decision-making capacity” can include anyone who is incapable of giving informed consent or who lacks sufficient understanding to qualify as valid informed consent. Decision-making capacity is a spectrum, with some individuals more capable of understanding and reasoning than others.



Don’t assume that just because an individual’s decision-making capacity is diminished that he or she cannot provide consent. Decision-making capacity is variable within groups and may change throughout the course of a study: someone with early Alzheimer’s Disease may be capable of providing consent, but as the disease progresses that person’s capacity will likely diminish.

In its draft guidance Informed Consent Information Sheet: Guidance for IRBs, Clinical Investigators, and Sponsors, FDA recommends additional safeguards for subjects with diminished decision-making capacity, such as:

  • Using an independent “qualified professional” to assess the consent capacity of potential subjects at the time of consent and in an ongoing manner
  • Establishing a waiting period to allow additional time for decision making
  • Using methods to enhance consent capacity, such as repetition, simplification and/or enlisting a subject advocate or trusted family members
  • Using questionnaires to assess understanding
  • Re-assessing a subject’s decision-making capacity for progressive disorders
  • Involving LARs as cognition declines
  • Including an assent mechanism
  • Involving the IRB or another third party to observe the consent process

Vulnerabilities like diminished decision-making capacity are a critical aspect of clinical research. Vulnerabilities have driven the regulations governing research, and honoring that mandate gives us continued permission to conduct research. Regulations can’t cover every person or situation, so it’s essential for research professionals to have a working mental construct for identifying vulnerability along with practical ways to mitigate its influencing factors.

To learn more about protecting vulnerable subjects, watch our webinar Protecting Vulnerable Subjects or review Safeguards for Vulnerable Subjects.