According to federal regulations, how are "children" defined?
Under federal regulations (45 CFR 46.402(a)), "children" are persons who have not attained the legal age for consent to the treatments or procedures involved in the research, under the applicable law of the jurisdiction where the research is conducted. It is jurisdiction-dependent, not a fixed age.
The answer
The correct definition comes from the U.S. Department of Health and Human Services regulations at 45 CFR 46.402(a) (Subpart D, the section that provides additional protections for children in research). It states that "children" means:
persons who have not attained the legal age for consent to treatments or procedures involved in the research, under the applicable law of the jurisdiction in which the research will be conducted.
The key phrase is "under the applicable law of the jurisdiction." Whether a research subject counts as a child is not a single national number — it depends on the state or locality where the study takes place and on the specific procedures involved.
Why the fixed-age options are wrong
Most versions of this question offer distractors like "anyone under 18," "anyone under 21," or "anyone under the age of majority." These are tempting because 18 is the common age of majority, but they are wrong for a precise reason:
- The regulation deliberately does not name an age. It ties the definition to consent law, which varies. In one state the legal age to consent to a particular medical procedure might be 18; in another it could be lower for certain treatments (for example, some states let minors consent to reproductive-health or mental-health services).
- Because the definition is procedure-specific, the same person could be a "child" in one study and not in another, depending on what the research involves and where it happens.
- "Under 21" reflects the old drinking-age intuition and has no basis in 45 CFR 46.
So any answer stating a hard number is incorrect; the regulation's answer is the jurisdiction-and-procedure-based one.
The bigger picture
This definition matters because Subpart D triggers extra protections once a subject qualifies as a child. Two ideas flow directly from it:
- Assent versus consent. Children generally cannot give legally effective informed consent. Instead, the IRB seeks the child's assent (their affirmative agreement to participate) plus the permission of one or both parents or guardians. Assent requirements scale with the child's age and maturity.
- Risk-based categories. Subpart D sorts approvable pediatric research into levels — minimal risk (46.404), greater than minimal risk but with prospect of direct benefit (46.405), greater than minimal risk without direct benefit but likely to yield generalizable knowledge (46.406), and research not otherwise approvable that requires federal-panel review (46.407).
Because consent age can differ by state, an investigator running a multi-site study must check each site's law — a subject who is an adult for consent purposes at one site may still be a child at another. That is exactly why the regulation frames the definition around jurisdiction rather than a fixed birthday.
| Jurisdiction-based (legal age to consent to the procedures involved) | Varies by state and procedure | Yes — this is the regulatory definition |
| Fixed age of 18 | Always under 18 | No — regulation names no fixed age |
| Fixed age of 21 | Always under 21 | No — no basis in the regulation |
| Whoever a parent calls a minor | Undefined | No — must be the legal consent age of the jurisdiction |
Frequently asked
What CFR defines children in research?
Children are defined at 45 CFR 46.402(a), which is part of Subpart D of the HHS regulations (the Common Rule's additional protections for children). It defines children by reference to the legal age of consent in the relevant jurisdiction.
Is a child always someone under 18 in research?
No. The regulation does not set a fixed age. A child is anyone who has not reached the legal age to consent to the specific treatments or procedures in the research, and that age varies by state and by procedure. Someone could be a child in one study but not another.
What is assent vs consent for children in research?
Consent is the legally effective informed agreement that adults provide. Because children usually cannot give it, researchers instead obtain the child's assent (their affirmative agreement to take part) along with the informed permission of a parent or guardian. Assent expectations increase with the child's age and maturity.
Does the age of consent vary by state for research?
Yes. Because 45 CFR 46.402(a) ties the definition to the applicable law of the jurisdiction, the age at which a person can consent — and therefore stops being a 'child' for a given procedure — can differ from state to state. Multi-site studies must check each site's law.
What extra protections apply to children in research?
Subpart D sorts pediatric research into risk-based categories (45 CFR 46.404–46.407), requires parental permission plus child assent, and limits how much risk is acceptable based on whether the child receives a direct benefit. Studies not otherwise approvable need special federal-level review under 46.407.