In the early 1990s, members of the Havasupai Tribe gave blood samples to researchers from Arizona State University. They believed the samples would be used solely to study diabetes, a major concern within their community. But without their knowledge or consent, the samples were later used to investigate schizophrenia, inbreeding, and ancient migration patterns—topics that not only violated their cultural beliefs but deeply damaged their trust in researchers.
The tribe sued, the university settled, and the case became a landmark example of how even when consent forms are signed, real informed consent can fail, especially when researchers don’t fully understand the vulnerabilities of the populations they’re working with.
It’s a cautionary tale that every new researcher should take seriously. Because while federal regulations highlight certain “vulnerable populations,” there are many more who face subtle, systemic, or situational risks that often go unacknowledged.
Let’s dig into 15 of those groups—and why ethical research means thinking beyond the usual checklist.
1. Undocumented immigrants
Undocumented people often fear that participating in research could expose their legal status, putting them or their families at risk. Even if personal data is anonymized, the power dynamics and fear of deportation can silence questions or concerns, undermining truly voluntary participation.
2. People experiencing homelessness
This group may be particularly susceptible to coercion, especially if research participation comes with incentives like meals or shelter. Beyond that, their lack of consistent access to communication, support systems, or medical care can make follow-up and comprehension more difficult.
3. LGBTQIA+ individuals
In hostile environments or communities where their identities are not protected, LGBTQIA+ participants may risk being outed through participation. Ethical research must ensure privacy, respect gender identity, and avoid assuming a one-size-fits-all approach.Research from The Trevor Project highlights how LGBTQIA+ individuals are vulnerable to discrimination and mental health challenges.
4. People in abusive or controlling relationships
Someone in a coercive relationship might feel unable to make independent decisions about research participation. They may also face risks if their partner discovers their involvement, especially in studies related to health, trauma, or autonomy. Further, research directly focusing on survivors of domestic violence may inadvertently re-expose survivors to past trauma.
5. Individuals in any organized religious groups
Individuals in organized religions, particularly conservative ones, may fear punishment or ostracization if they’re seen engaging in outside research. Their fellow members if non-conservative views or practices are revealed.In other words, data exposure could result in significant social consequences.
These contexts can dramatically alter what “voluntary” really means.
6. People with low health literacy
If a participant doesn’t fully understand medical terms or research jargon, they may agree to studies without comprehending the risks. It’s not enough to hand over a consent form, we must meet people where they are, with plain language and opportunities to ask questions.The CDC defines health literacy as essential to good health outcomes—and research is no exception.
7. Active military personnel (especially enlisted members)
In military hierarchies, it can be hard to say no, especially if the request is coming from a superior. Enlisted members may feel pressured to participate even when they’re uncomfortable, making power dynamics a major ethical concern.
Researchers from the Army Public Health Center’s Behavioral and Social Health Outcomes Practice Division partnered with APHC Soldiers to run a data collection training exercise to assess social and behavioral health risk factors of Soldiers. Source.
8. Precariously employed individuals + people living in poverty
For people juggling multiple jobs or surviving paycheck to paycheck, research incentives can be coercive—even when unintended. If participating means being able to pay rent or buy groceries, the power imbalance is real.
9. People in crisis (natural disasters, medical emergencies, etc.)
People in acute crisis situations may be more focused on survival than fully understanding a study’s risks. Timing matters. Ethical researchers know when to pause and when to ask better questions about readiness.
10. Refugees and asylum seekers
Displacement, trauma, language barriers, and cultural differences all contribute to heightened vulnerability. Refugees may feel compelled to participate out of gratitude or confusion about institutional authority.
11. People facing digital or technological barriers
In a world of online surveys and digital consent forms, people without internet access or digital literacy are left behind or pressured to sign documents they don’t understand. Accessibility isn’t just physical, it’s digital too.
12. First-generation college students
They may not seem “vulnerable” at first glance, but first-gen students often face information gaps, imposter syndrome, and financial pressure. In research settings, they may feel obligated to participate—especially if faculty or college departments are involved.
13. People subjected to systemic racism or historical trauma
For many Indigenous, Black, and Latinx communities, past abuses—like the Tuskegee Syphilis Study or the Havasupai case—still shape how they perceive research today. Trust is fragile, and rightly so. Respecting that history is part of doing ethical work.
This JAMA article explores how historical trauma impacts medical and research mistrust.
14. Caregivers of people with disabilities or chronic illnesses
These individuals may feel emotionally tied to research in hopes of finding solutions for their loved ones. But that hope can blur the lines of informed consent, especially if they’re participating in studies alongside or on behalf of someone else.
15. Non-native researchers in host countries
Non-native researchers doing research abroad might lack the awareness and cultural understanding to engage with communities in non-exploitative ways. Cultural misunderstandings, language barriers, and power imbalances can lead to unethical outcomes, even with good intentions.
What This Means for You as a Researcher
If you’re new to human subjects research, it’s tempting to focus on the standard categories of vulnerability—children, prisoners, pregnant people. And yes, those protections are essential.
But real-world ethics require more.
They require asking deeper questions about power, access, trust, and history. They require slowing down long enough to consider who’s not at the table, or who’s there but doesn’t feel safe enough to speak freely.
Want to make sure your research is ethical, inclusive, and human-centered? Explore our PPRE course and learn how to protect the people who make your work possible.