Ethical challenges of capacity assessment in neurodevelopmental and intellectual disabilities

Abstract

Individuals with neurodevelopmental disorders and intellectual disabilities face research exclusion due to complex consent processes. This article highlights how fluctuating capacity challenges binary assessment models. We propose ongoing capacity monitoring, independent consent monitors, and adaptive tools to ensure ethical inclusivity and respect for participant autonomy in clinical research.

Introduction

Individuals with neurodevelopmental disorders (NDD) and intellectual disability (ID) have been historically underrepresented in clinical research, limiting equitable access to potential benefits of scientific advances and novel therapeutics. [1–2] In neurology in particular, research commonly involves participants with variable cognition, communication, and executive functioning, making the informed consent process a frequent site of exclusion rather than inclusion [3].

Informed consent requires adequate disclosure, voluntariness, and decision-making capacity. Capacity in research settings is commonly evaluated with reference to four abilities: understanding relevant information, appreciating how the information applies to one’s situation, reasoning about options, and communicating a stable choice. Although these criteria are widely recognized across research ethics frameworks, the operational processes described in this commentary largely reflect regulatory and clinical practices used in the United States [4]. In NDD/ID, these abilities may be uneven (e.g., strong preference expression but limited abstract reasoning), environment-dependent (fatigue, anxiety, unfamiliar settings), and time-varying (e.g., encephalopathy, epilepsy-related fluctuations, neurodegeneration, or treatment response).

Treating capacity as a binary “yes/no” trait risks both overprotection (unnecessary exclusion) and under protection (inadequate safeguards).

Although multiple instruments exist, there is no universally adopted gold-standard capacity tool across jurisdictions and institutions, and capacity determinations are often implicit rather than systematic [5]. When capacity is uncertain or expected to fluctuate, more structured approaches can improve consistency and transparency. The MacArthur Competence Assessment Tool for Clinical Research (MacCAT-CR) is widely used, but like all instruments it requires trained administration and does not eliminate the need for tailored communication and supports [6].

Below we outline three pragmatic strategies that can be implemented across a range of trial designs to better align consent practices with participant autonomy and welfare (Fig.1).

Fig. 1.

Pragmatic strategies for implementing inclusive consent practices

Iterative capacity monitoring rather than a one-time gatekeeping assessment

Capacity is commonly assessed only at enrollment. For populations in whom capacity can change, reassessment should be treated as part of ongoing consent, not as a repeated barrier. Pragmatically, sites can use a brief, visit-level check-in that reviews purpose, procedures, key risks, and the voluntary nature of participation, with documentation of the participant’s understanding and assent/dissent. When the participant cannot provide full consent, re-confirming ongoing assent and observing for dissent remains ethically important [3, 7].

Legally authorized representatives (LARs) can contribute to capacity monitoring because they observe participants across settings and over time. However, their involvement should not replace direct engagement with the participant. A useful operational standard is: (a) communicate with the participant first using accessible language and appropriate communication tools (e.g., simplified language, visual aids, augmentative and alternative communication devices, or sign language); (b) then consult the LAR for contextual insight; and (c) document any discrepancy and the rationale for decisions about continued participation.

Independent consent monitors to support surrogate decision-making in uncertain benefit settings

When participants lack baseline capacity (e.g., early-onset NDD/ID) or cannot articulate prior values, LARs may rely on best-interest judgments. This can be particularly difficult in trials where direct benefit is uncertain and equipoise is required [7]. An independent consent monitor—knowledgeable about the study but not part of the clinical or research team—can help ensure that risks, alternatives, and voluntariness are presented neutrally and that LAR decisions reflect the participant’s preferences to the extent they can be elicited.

Independent monitors may be most useful in higher-risk studies, first-in-human trials, or protocols with complex procedures. Where staffing is limited, centralized or remote monitoring models (e.g., cross-site ethics consultants) can provide similar safeguards without requiring every site to maintain local expertise [3, 8].

Adaptive consent practices that meet participants where they are

Many tools used in pediatric decision-making can be repurposed for NDD/ID research participation. Adaptive practices include simplified assent materials for participants when feasible, pictorial or multimedia explanations, teach-back methods, and procedure rehearsal (e.g., mock MRI) [9]. Simplified assent materials are typically designed for the participant rather than the legally authorized representative, but their usefulness depends on the participant’s literacy and communication abilities. For individuals functioning at early stages of communication development, non-written modalities, such as graphic aids or visual tools, experiential demonstrations, or caregiver-mediated communication, may be more appropriate than written documents. In this context, “accessible language” refers to information presented in formats that accounts for the participant’s cognitive and communication abilities, such as simplified vocabulary, shorter sentences, familiar words, visual tools, or multimodal explanations. These approaches are not “less rigorous”; they are methods of delivering the same material in a way that increases comprehension and voluntariness. Importantly, communication and decision-making tools should be individualized, culturally and linguistically appropriate, and may include assistive communication technologies, caregivers familiar with the participant’s communication style, or structured visual and experiential aids.

Communication in individuals with neurodevelopmental and intellectual disabilities is highly heterogeneous and may involve spoken language, sign language, augmentative or alternative communication devices, gesture-based communication, or caregiver-mediated interpretation. Ethical consent processes should therefore consider the broader “architecture” of communication, by allowing a participant to indicate agreement, refusal, or understanding through a communication method accessible to them, rather than relying solely on verbal explanations or written documents. Participants may also experience vulnerabilities related to social desirability bias, power dynamics with clinicians, sensory sensitivities, or difficulty processing abstract risk concepts. Reasonable adjustments, such as extended time for discussion, familiar communication partners, simplified visual explanations, or staged consent discussions across multiple visits, can help mitigate these barriers and support more authentic expression of preferences.

Operationally, investigators can pre-specify an “accessibility menu” in the protocol: plain-language summaries; standardized visual aids; flexible timing to reduce fatigue; quiet rooms; augmented communication tools; and an explicit plan for documenting assent/dissent.

Doing so also improves reproducibility across sites and reduces ad hoc variability in consent quality.

Conclusion

Inclusive clinical research in NDD/ID is ethically necessary and increasingly feasible, but it requires consent processes that account for contextual and fluctuating capacity. Iterative capacity monitoring, independent consent monitors, and adaptive consent practices can reduce inappropriate exclusion while strengthening safeguards. Future work should evaluate efficient reassessment workflows, standardized accessibility tools for consent communication, and international policy approaches that support consistent and inclusive capacity assessments across research environments.

Abbreviations

CIOMS

Council for International Organizations of Medical Science

DSRD

Down Syndrome Regression Disorder

ID

Intellectual Disability

LARs

Legally Authorized Representatives

MacCAT-CR

MacArthur Competence Assessment Tool for Clinical Research

MRI

Magnetic Resonance Imaging

NDD

Neurodevelopmental Disorders

WHO

World Health Organization

Authors' contributions

JDS conceptualized the manuscript and was the primary contributor in writing the manuscript regarding capacity fluctuation and assessment in clinical research involving neurodevelopmental disorders. LK and MCL contributed to the drafting of the abstract and introduction sections. JK provided critical revisions regarding the ethical framing of the manuscript and bioethical considerations. MSR provided critical revisions for important intellectual content related to clinical research and neurological disease processes. All authors read and approved the final manuscript.

Funding

No funding.

Data availability

There is no associated data with this manuscript.

Declarations

Ethics approval and consent to participate

Not applicable. This study is a commentary review of previously published works and did not require ethics approval or consent.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.