Caring for those in Need

Why Are People with Intellectual and Developmental Disabilities Left Out of Clinical Research Trials?

“Clinical trials should, to the extent possible, enroll a population that is representative of the diversity of the population that will use the medical product, if approved.”  1 That makes sense, right? Unfortunately, people with intellectual and developmental disabilities (IDD) are typically left out of clinical trials. They are not alone. Other historically underrepresented populations include people with physical disabilities and people with mental illness.

BY Lorene Reagan, MS, RN | February 2024 | Category: Healthcare

Why Are People with Intellectual and Developmental Disabilities Left Out of Clinical Research Trials?

 What is a Clinical Trial?

Clinical trials provide critical evidence regarding whether a medical product, such as a medication or medical device, is safe and effective. 

What are the Barriers to Participation in Clinical Trials for People with IDD?

According to an article published by the American Institutes for Research (AIR®) Center on Knowledge Translation for Disability and Rehabilitation Research,2 approximately three-quarters of clinical trials funded by the National Institutes of Health, directly or indirectly exclude adults with intellectual disabilities. Some study exclusions specifically disallowed participation by those with cognitive challenges, reduced functional capacity, or the inability to read or write. Additionally, researchers may not have considered the need for accessible study materials, the support needed for people with IDD to participate meaningfully, or the importance of ensuring people with IDD, not proxies, provide direct input, as study participants. 

Why Have People with IDD Historically Been Underrepresented in clinical trials?

Concerns about informed consent and the capacity to understand the benefits and risks of clinical trial participation, and the potential for exploitation are often cited as reasons for excluding people with IDD from clinical studies. While important, these risks can and should be mitigated through careful attention to inclusive study design. 

Why is This Such a Problem?

Excluding people with IDD from clinical trials means the treatments used for a variety of conditions have not been evaluated to determine the benefits or the risks of use in people with specific developmental conditions. One example of this is research involving drugs used to treat Alzheimer’s disease. Even though a high percentage of people with Down syndrome will eventually develop dementia by age fifty-five, very few clinical trials involving Alzheimer’s disease have included people with Down syndrome.3

Hope is on the Horizon

In September of 2023, the National Institutes of Health (NIH) formally designated people with disabilities as a population with health disparities, allowing greater opportunities to include people with disabilities in research efforts. “Research to understand the barriers and unmet needs faced by people with disabilities, and to develop effective interventions to address them, is needed. This designation will help to improve access to healthcare and health outcomes for all people.”

In addition, the US Food and Drug Administration (FDA), the entity responsible for approving drugs and medical devices, recently sought public input into a proposal to address inequities in study design, by requiring those who are conducting clinical trials to use disease prevalence and incidence data by demographic group, to inform clinical trial enrollment by those who are expected to use a particular drug or device. This means information about disability status must be considered in the study design, to ensure that people with disabilities are not unnecessarily excluded. 

As advocates for people with IDD, we play a critical role in supporting full and meaningful participation in all activities, including clinical research trials. Understanding the history of exclusion and the efforts to promote inclusive study design and implementation will help ensure that people with IDD have the same opportunities as others to participate in research activities.  


1.         Public Workshop to Enhance Clinical Study Diversity. 2023. US Food and Drug Administration & Clinical Trials Transformation Initiative.

2.  Inclusive Methods for Engaging People with Intellectual and Developmental Disabilities in Research Practices. 2023. American Institutes for Research® (AIR®) Center on Knowledge Translation for Disability and Rehabilitation Research.

3.         Excluding People With Disabilities From Clinical Research: Eligibility Criteria Lack Clarity And Justification. 2022. Health Affairs.

4.         NIH designates people with disabilities as a population with health disparities. 2023. National Institutes of Health (NIH). 


Lorene Reagan, RN, MS, has over 35 years of experience in the field of intellectual and developmental disabilities (IDD). Lorene is the former Bureau Chief for IDD services in New Hampshire, was Manager of Care Management for a Medicaid managed care organization, and a Principal in a consulting firm focusing on state Medicaid policy and operations. She is the former Director of Public Relations at IntellectAbility ( which provides tools and training to agencies, governmental entities, and supporters of people with intellectual and developmental disabilities to foster early recognition and mitigation of health risks and promote health equity for people with IDD. Currently, Lorene provides strategic consulting services focusing on health risk management and health equity for people with IDD. 

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