Assent (in Research)

Assent is the affirmative agreement of a prospective research subject who lacks the legal capacity to give informed consent on their own behalf — typically a minor — to take part in a research study. Under 45 CFR 46 Subpart D (§46.402(b), §46.408), assent is distinct from, and required in addition to, the informed permission of a parent or legally authorized guardian: a child's willingness to participate does not substitute for parental permission, and parental permission does not substitute for the child's own assent where an Institutional Review Board (IRB) has determined the child is capable of providing it. Critically, assent must be an affirmative 'yes' — the regulation explicitly states that a child's mere failure to object, absent some affirmative agreement, may not be construed as assent. The IRB decides, on a study-by-study or even subject-by-subject basis, whether assent is required, how it should be solicited (verbally, in writing, or via an age-appropriate script), and whether it may be waived under the conditions set out in §46.408(a).

ByCASRAI Editorial Board

· Last updated 23 Jul 2026

Worked examples

Is an instance

A 12-year-old enrolled in a pediatric oncology trial reviews an age-appropriate assent form with the study coordinator, asks questions about the additional blood draws, and signs to indicate agreement; her parents separately sign the informed-permission document. Both are required before she is enrolled.

Is an instance

An IRB reviewing a minimal-risk survey study of 16- and 17-year-olds determines, given the subjects' age and the low-risk nature of the research, that a brief spoken assent script read by the researcher satisfies §46.408, and does not require a separate written signature.

Looks similar, but isn't

Not an instance

A 7-year-old who does not cry or resist when a study procedure is administered has not thereby given assent — §46.402(b) explicitly excludes passive non-objection from counting as affirmative agreement.

Not an instance

Enrolling a 15-year-old solely on the strength of her parents' signed permission form, without any attempt to solicit the child's own agreement, does not satisfy Subpart D once the IRB has determined the subjects are capable of assenting.

In human subjects research, assent and consent are not interchangeable. Informed consent is the legally operative agreement given by someone with the authority to agree on their own behalf — an adult research subject, or, for a child, a parent or guardian providing what 45 CFR 46 Subpart D calls permission rather than consent proper. Assent is the child’s own affirmative agreement to participate, sought in addition to that permission whenever the reviewing Institutional Review Board (IRB) determines the child is developmentally capable of providing it.

Where the Requirement Comes From

The assent requirement is set out in the Common Rule at 45 CFR 46 Subpart D, “Additional Protections for Children Involved as Subjects in Research.” Section 46.402(b) supplies the operative definition: assent means a child’s affirmative agreement to participate in research, and mere failure to object, absent affirmative agreement, may not be construed as assent. Section 46.408 then sets the procedural requirements — when assent must be sought, how the IRB should account for the ages, maturity, and psychological state of the children involved, and the circumstances under which the IRB may waive the assent requirement altogether (for example, where the research holds out a prospect of direct benefit important to the child’s well-being and is available only in the research context).

Why Assent Exists Alongside Parental Permission

Parental or guardian permission establishes that enrolling the child is legally and ethically authorized. It does not, by itself, establish that the child understands or is willing to take part. Assent addresses that second question directly: it treats the child as a participant with a voice in the decision, proportionate to their developmental capacity, rather than as someone research is simply done to once a parent has signed. Neither element substitutes for the other — both are independently required unless the IRB specifically waives one under the regulatory conditions that permit a waiver.

How IRBs Determine Whether — and How — Assent Applies

Subpart D does not set a fixed age at which assent becomes required; that determination is left to the IRB, considering the ages, maturity, and psychological state of the children involved in the specific research. In practice this means the same protocol can call for a formal written assent process for a 16-year-old cohort and a simplified verbal script, or no assent solicitation at all, for a study enrolling toddlers who cannot meaningfully understand what is being asked of them. IRBs also determine the manner assent is documented — which can range from a signed, age-appropriate assent form mirroring the adult consent document, to a brief spoken explanation with a documented verbal agreement, depending on the study’s risk level and the subjects’ capacity.

Assent vs. Consent: The Core Distinction

The clearest way to hold the two apart: consent (or, for a minor, parental permission) is the legally authorizing act; assent is the child’s own agreement, and it is affirmative by definition — silence, passivity, or the absence of protest is not assent under §46.402(b). A fuller side-by-side treatment of how the two requirements interact, including when assent can be waived, is available on CASRAI’s Informed Consent vs. Assent comparison.

Related CASRAI Resources

Informed consent — the general operational definition and requirements under the Common Rule.
45 CFR 46 Subpart D (Additional Protections for Children in Research) — the full regulatory structure governing pediatric research risk categories and permission/assent requirements.
Vulnerable Populations in Research
IRB (Institutional Review Board)
Common Rule (45 CFR 46)
Informed Consent vs. Assent — comparison

Use in your systems

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