01 · The Question
Must researchers go back and obtain consent once participants become adults?
A research project enrolled participants when they were children. Their parents gave permission, and the children assented where required. Years later, those participants have reached the legal age of consent.
Does the research team now need adult consent from everyone?
Often yes, but the precise answer depends on what research is still occurring. If investigators continue interacting or intervening with participants after they become legally capable of consent, their own informed consent ordinarily must be obtained unless the requirement has been appropriately waived. If no further contact occurs but identifiable information or biospecimens remain in research use, consent may still be required unless an IRB approves a waiver. If the remaining materials are not identifiable under the applicable regulatory framework, the analysis can be different.
03 · What You Need to Know
The answer depends on what continues after childhood
Parental permission and child assent are not prospective adult consent
When a child enters research, parental or guardian permission and child assent may provide the required authorization for participation under the protections governing research with children.
Those decisions do not automatically become the participant's legally effective informed consent when the participant later becomes capable of consenting for themselves.
OHRP explains that parental permission and child assent are not equivalent to legally effective informed consent for the now-adult participant. If research covered by the Common Rule continues, investigators need to consider whether the participant's own consent must now be obtained.
Ongoing interactions or interventions ordinarily require adult consent
This is the clearest situation. If researchers will continue conducting interviews, administering surveys through direct interaction, collecting specimens, performing examinations, delivering interventions, or otherwise interacting or intervening with the participant after the participant reaches legal consent age, informed consent ordinarily needs to be obtained from that participant.
An applicable IRB-approved waiver can change this requirement, but the earlier parental permission does not by itself authorize future adult participation.
The operational transition when a participant reaches legal consent age during a longitudinal study should therefore be anticipated in the protocol.
No further contact does not automatically mean no consent issue
Suppose the participant completed every study visit while still a child. Researchers now intend only to continue analyzing identifiable private information or identifiable biospecimens collected during childhood.
Under the Common Rule, obtaining, using, studying, analyzing, or generating identifiable private information or identifiable biospecimens can constitute research involving human subjects. OHRP therefore explains that investigators may need to obtain the now-adult participant's consent for continued research use unless an IRB determines that the requirements for waiver are satisfied.
This is an important correction to the intuitive idea that re-consent matters only when researchers want to bring someone back to the laboratory.
What continues after legal consent age?
General Common Rule implication
What researchers should consider
Interviews, visits, surveys involving interaction, procedures, interventions, or new specimen collection
Adult informed consent ordinarily required
Obtain legally effective consent before continued participation unless an IRB-approved waiver applies.
Research use of identifiable private information or identifiable biospecimens already collected
Can remain human-subjects research
Adult consent may be required unless the IRB approves a waiver.
Research using information or biospecimens that are not identifiable under the applicable framework
May not constitute human-subjects research under the Common Rule
Confirm the regulatory determination rather than assuming de-identification is sufficient.
Identifiability is therefore crucial
The regulatory treatment of previously collected materials can turn on whether researchers obtain or use information or biospecimens in an identifiable form.
Researchers should not casually equate coded with nonidentifiable. Whether coded information remains identifiable depends on the circumstances, including whether investigators can readily ascertain the identity of the individuals under the applicable regulatory framework.
When uncertain, seek an institutional or IRB determination rather than independently declaring that a coded data set has left human-subjects regulation.
An IRB can sometimes waive adult consent
Re-contacting every participant years after childhood enrollment may sometimes be impracticable. Participants may have moved, contact information may no longer work, or the cohort may have been established many years earlier.
That difficulty does not itself eliminate consent. Instead, an IRB can determine whether the applicable waiver criteria under 45 CFR 46.116 are satisfied.
Under the current general waiver provision, the IRB ordinarily must find that the research involves no more than minimal risk, could not practicably be carried out without the waiver, will not adversely affect subjects' rights and welfare, satisfies the additional criterion concerning identifiable information or biospecimens when applicable, and provides additional pertinent information afterward when appropriate.
“We lost contact” is not automatically a waiver
A research team should document why obtaining adult consent is impracticable rather than simply inconvenient. The IRB makes the waiver determination.
A study with outdated contact details should also distinguish inability to locate some participants from a decision not to attempt re-contact at all. The protocol, available resources, risks, data involved, and scientific consequences may all be relevant to the IRB's assessment.
The adult participant may decline continued participation
If adult consent is sought, the participant must have a genuine choice. Researchers should not present the new form as an administrative update that the participant is expected to sign because they have already spent years in the study.
The participant may decide that continued participation is acceptable or may decline. What happens to information or biospecimens collected before withdrawal depends on the approved protocol, applicable regulations, what the participant was originally told, and the nature of the research records.
Researchers should explain the consequences accurately rather than promising that withdrawal necessarily means every previously collected datum can or will be destroyed.
Re-consent should reflect the research that remains
A participant who entered a ten-year study at age 12 does not necessarily need to reread a document written as though no research has yet occurred.
The adult consent process should accurately explain the participant's current situation: what has already been collected, what activities remain, how information and specimens will be used, foreseeable risks, potential benefits where applicable, confidentiality, relevant alternatives, voluntary participation, and the consequences of discontinuing further participation.
The IRB-approved materials should fit the actual stage of the research.
Consent authority may change before the general age of majority
Researchers should again be careful with the shorthand of “turning 18.” Under HHS regulations, children are defined according to whether they have reached the legal age for consent to the treatments or procedures involved in the research under applicable law.
Some participants may acquire legal authority to consent earlier in particular circumstances. Conversely, legal questions may be more complicated for adults who lack decision-making capacity. The transition should be based on actual consent authority, not a birthday rule detached from applicable law.
Adult consent and parental permission should not coexist by habit
Once the participant has legal authority to consent for themselves, researchers should not continue treating the parent as the decision-maker simply because that was the study's established routine.
Parents may remain involved if the adult participant wishes and if doing so is appropriate, but their earlier permission does not substitute for the adult participant's own legally effective consent.
Watch Out
Do not automatically send an adult consent form to every former child participant without first identifying what research remains. Ongoing intervention, continued use of identifiable materials, and research using nonidentifiable materials can raise different regulatory questions.
06 · What This Means for You
Classify what remains before deciding whether adult consent is needed
For every participant approaching legal consent age, identify what the study will still do with or to that person. That classification makes the consent question considerably easier to manage.
A simple decision framework
If new interactions or interventions will occur
Obtain legally effective informed consent from the participant unless an IRB-approved waiver applies.
If only identifiable private information or identifiable biospecimens remain in research use
Determine whether adult consent is required or whether the IRB can approve an applicable waiver.
If only nonidentifiable information or biospecimens remain
Confirm whether the continued activity constitutes human-subjects research under the applicable regulatory framework.
If participants cannot practicably be re-contacted
Present the circumstances to the IRB and address every criterion of the applicable consent-waiver provision.
If the participant declines adult consent
Do not conduct new activities requiring that consent and follow the approved procedures for withdrawal and previously collected materials.
For prospective longitudinal studies, include these pathways from the beginning. Tell families and adolescents that consent authority may change during follow-up and explain, where appropriate, that participants will later be asked to make their own decision.
This approach also avoids a surprisingly common conceptual mistake: treating adulthood as an administrative change in the participant record rather than a change in who has authority over continued research participation.
07 · A Quick Checklist
Before deciding whether adult consent is required, check what remains
For participants originally enrolled as children, check:
Determine when each participant becomes legally capable of consenting to the research activities involved.
Identify whether any research interactions or interventions will occur after that transition.
Identify whether previously collected private information or biospecimens remain identifiable and in research use.
Obtain adult informed consent when required rather than relying on childhood assent or parental permission.
If consent cannot practicably be obtained, determine whether the IRB can approve a waiver under the applicable criteria.
Ensure the adult consent materials accurately describe what research has already occurred and what remains.
Plan how refusal of adult consent will affect future activities and previously collected information or specimens.
Document the IRB's determination when the remaining research is considered outside the scope of human-subjects research.
11 · Cite this Guide
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