Informed consent


Informed consent

For an individual to participate in a research project, they must provide informed consent. This is a principle that is central to the ethical undertaking of all biomedical research, and one that is enshrined in global human research guidelines and regulations via the Nuremberg Code (1947) and Declaration of Helsinki (World Medical Association, 1964; most recent update, 2013). Informed consent as a process is one in which both research participant and researcher (or the person taking consent if different from the researcher) need to take an active role. It can be broken down into 5 main steps:

  1. Competency
  2. Consent
  3. Voluntariness
  4. Understanding
  5. Disclosure


Competency relates to an individual's ability to provide informed consent (competency is a legal definition) and if individuals are deemed to be non-competent then they will be unable to provide consent. They can, however, have the power of consent delegated to another individual such as a family member or a carer.

Who is competent?

Adults (often those over 18 years of age, but definitions may vary by country) who have no conditions which affect their ability to make sound decisions. The presence of mental health conditions and progessive disorders such as Alzheimer's disease may render participants non-competent.

Children are often described as non-competent (due to age) but in certain cases can still be allowed to take such decisions. For example, in the UK, children can be classed as Gillick competent, which allows them to give consent without parental/guardian interference.



To enable individuals to give fully informed consent, they must be fully apraised of all aspects of the study. This is the element of disclosure. All elements of the study process, including all potential risks and benefits, must be disclosed at this point, and the individual given the opportunity to ask questions.

How to inform?

Information is normally provided in the form of a written information sheet along with a verbal explanation from a member of the study team.

Alternative methods have been successfully used including audio recordings and filmed study overviews for people unable to read such literature.


Providing participants with all the information is only one aspect of the informing process; the person taking consent must also assess whether the individual in question understands what they are signing up to. This ensures they have read the information, and know what their role in the study will be and what it entails. 

Assessing understanding

Some projects have taken the approach of giving people an assessment before asking for consent (Personal Genome Project, Harvard) but in most cases this is done through a pre-consent conversation during which potential research subjects are asked various questions about the study. 



Individuals must provide consent by their own free will, free from coercion and any other influences. It is up to the individual taking consent to determine that the persons providing consent are doing so on their own behalf with no undue influence from other parties or external factors.

Coercive factors

Coercive factors can vary from culture to culture, although the two most commonly discussed are monetary influence and the potential for access to better healthcare provision if a clinical element is involved.

Individuals may also be influenced by family members or other key influencers, including medical staff.

Ethics committees look for potential coercive factors when reviewing a study for approval and may ask for these factors to be removed.




The provision of consent is usually the final step in this process. This is normally provided in a written form alongside the signature of the researcher (or other individual who is taking consent), although other methods can be used in cases where individuals are unable to write (for example, use of thumbprints).

Consent is, however, not always the final step, for two main reasons:

  1. Should new information regarding the study become available, this will need to be communicated to the study participants and may require re-consenting if the changes are deemed to be significant.
  2. Study participants may withdraw from a study at any point, in which case their consent is no longer valid.

Study withdrawal

Individuals who provide consent to be part of a research project have the right to withdraw from the study at any time if they no longer wish to be involved.

It can, however, be difficult to remove data already collected from a subject within a study. Therefore, individuals must be made aware that if they withdraw their consent, it may not be possible to remove this data.