Why Are We So Afraid To Pay Research Participants?
By Jake Eberts, member, board of directors, 1Day Sooner, and Lindsay McNair, principal consultant, Equipoise Consulting
The traditional approach to payment of research participants is broken. There is a growing movement of research ethicists and other stakeholders who point out that the ethical concerns of under-compensating research participants are significantly greater than the ethical concerns of overpayment, particularly as we look at research participation through the lens of justice and equity and to reduce barriers to participation. 1Day Sooner — along with 62 other signatories — recently published an open letter calling for a reassessment of how we pay research participants in the American Journal of Bioethics. In this letter, we urge readers to shed the excessive concern over undue influence and to embrace a more just and generous approach to compensation. Here, we expand on our reasoning and consider the next steps in this compensation revolution.
For our purpose here, “payments” are compensation for the time, inconvenience, and effort of research participation. This does not include mere reimbursements covering actual study expenses for participants, such as travel expenses, prepaid meal vouchers during study visits, or free clinic parking — even when expenses are considered more broadly, such as paying for childcare when a parent has a study visit or covering grocery delivery costs during a time of expected post-treatment adverse effects.
Why Have We Been Cautious With Participant Payment?
Many of our historical practices in human research participant oversight stem from a culture of paternalism. This is unsurprising, given the very roots of field’s bible, the Belmont Report, which was crafted with the terrible abuses of highly vulnerable participants in medical research fresh in the public consciousness. Drawing on this legacy and the related federal regulations, oversight bodies, including IRBs, rightly believe their primary responsibility is to protect research participants. But for many IRBs, this includes protecting them from making decisions that they feel are not in the participant’s best interest, even if the participants were entirely competent to make those decisions for themselves. There is inevitable tension here with the Belmont Report, which also demands respect for the autonomy of participants.
This tension comes to a head in discussions about compensation, where there has historically been a pervasive fear of payment overriding the rational capacity of a prospective participant to assess risks and benefits, negating their ability to provide informed consent. In other words, there is a fear they are unduly influenced (or unduly induced) by the money. As our open letter notes, while this concern may seem intuitive at first, cracks begin to show under further scrutiny and empirical investigation, as we discuss in the next section. (Colloquially, people may worry that participants are outright coerced by money as well. This is a misuse of the term, however, because coercion necessarily involves a threat or use of force. An offer can be unfair, exploitative, or unjust, but it cannot on its own be coercive unless paired with a threat by the offerer.)
It’s important to remember that influence in itself is not prohibited from a regulatory or ethical perspective; factors that facilitate research participation that may make it more likely for someone to agree to be in a study, like convenient study visit schedules, are not seen as a problem.
There are also clear examples of nonmonetary undue influence. For example, a graduate student might be capable of deciding whether to join a medical trial, but if the trial is run by their advisor, then there’s a risk of implicit (or even explicit) pressure to join the study to stay in the favor of the advisor. Given the inherent risk of such a scenario, an institution could be justified in prohibiting graduate student participation in intensive research run by figures in their department.
But what exactly qualifies as undue influence with money is much less clear, and regulatory guidance does not provide a bright line. FDA guidelines from 1998 say that payments should be “just and fair” but that they should not “present an undue influence, thus interfering with the potential subjects’ ability to give voluntary informed consent.” Like the underlying regulations in 21 CFR 50.20, what exactly constitutes undue influence is not defined. FDA guidance from 2018 does clarify that reimbursement of study-related expenses was not considered a problem, and in specific questions has confirmed that reimbursement includes costs like childcare and household support during studies. In the Office for Human Research Protections (OHRP), which oversees most federally-funded clinical research, there has been movement toward more liberal approaches to compensation. OHRP hosted a workshop on the subject in 2022, where a representative stated that IRB members worry far more about undue influence from compensation than OHRP does.
The inability of regulators to define an exact point of undue influence via compensation is unsurprising, because the task is literally impossible: What constitutes undue influence will always vary from person to person. Just $1,000 could be a life-changing sum of money for one person and mere pittance for the next, after all.
Does Participant Payment Really Cause Undue Influence?
Previous research suggests that among the general public, IRB members, and even research participants themselves, there is a widespread belief that compensation can easily cause undue inducement. This has led to what Largent and Fernandez Lynch dub “payment conservatism,” or an inherently cautious attitude toward compensation that is far more concerned with whether a study is paying too much, rather than too little. What if this approach is mistaken?
In our open letter, we cite a dozen studies — including surveys, experiments, and qualitative interviews with research participants — that have failed to find convincing evidence of the phenomenon in both the industrialized world and developing world. Participants certainly adjust their tolerance of risks in response to payment and may even experience regret when a study turns out to be more demanding or less successful than they anticipated, but this is not inherently a sign of undue influence.
But greater tolerance of risk is not necessarily problematic in the context of otherwise well-regulated medical research, where an IRB has assessed a study against regulatory criteria that include a reasonable balance of risks and benefits. Adding compensation to participants does not change those risks; risks that are reasonable without compensation do not become greater when compensation is added (and IRBs do not consider compensation as a benefit), so denying compensation for participants does not provide any additional protections.
The Hidden Costs Of A Conservative Payment Approach
Even if there is a substantial risk that compensation could cause undue inducement, it’s not clear that lowering or avoiding payments actually protects anyone. Instead, both the burdens and potential benefits of research participation are shifted in less equitable ways.
Notably, in an attempt to avoid undue influence, some have proposed compensation schemes that are themselves unjust. For example, one popular model of compensation in academic literature, the wage payment model, bases payment on the prevailing wage of unskilled labor in the local economy, or even the minimum wage. But that presupposes that these wages are reasonable and fair, which is a tenuous assumption — after all, in countless major metropolitan areas, even a single person without children can’t support themselves on just low-paid wage labor, let alone the minimum wage. Why, then, would we assume that such pay is inherently reasonable for research participation?
Recent publications have described the financial toxicity of cancer clinical trials, showing that increased requirements for travel to a study site, missed work, and other factors resulted in an average of $600 per month of unreimbursed, nonmedical expenses for participants in early cancer trials. People with household incomes under $50,000 are 30% less likely to participate in cancer clinical trials, in part because of the concern about additional travel, missed work, and expenses. For these trials, lower payments translate to lower access to potentially cutting-edge research by those less well off.
The problem is flipped in early-stage healthy, non-patient trials, where participants are more likely to be low-income. In these cases, lowering payment levels out of fear of undue inducement may shift burdens in a different direction. Suppose a highly intensive, week-long inpatient healthy volunteer Phase 1 trial is approved by an IRB on the condition that the $5,000 proposed payment be reduced to $2,000 so that participants “aren’t just enrolling for money.” There may well be some for whom $2,000 is still worth it, but there also would be those who are wealthier and for whom the lower amount is too little to justify the time, inconvenience, pain, and discomfort. In other words, lowering payments, on average, concentrates research participation among those with worse financial circumstances. It is only wealthier prospective participants who are “protected” from undue influence when payments are lowered, even though lowering payment is done in the name of protecting financially vulnerable people.
What Are The Next Steps?
The vagueness of regulatory guidelines means there is room for reform within the field of research ethics and among trial sites and sponsors as this emerging consensus against payment conservatism spreads. Hesitant sponsors and IRBs can be pointed to our open letter, for example, for a succinct and easily accessible resource in support of a presumption that payment levels are not too high (and if anything, that we should be asking if payments are enough, not too much).
IRBs should not be the blockade to fair payments, although other stakeholders often cite them as one; in a review of 10,000 recent protocol submissions to WCG IRB, Fitzgerald found no examples where the IRB had raised concerns about proposed overpayment of participants or that the IRB had asked for overall payment amounts to be reduced. Sponsors and CROs can take a leadership role on this issue by considering the compensation issue early and proposing reasonable and generous compensation plans in clinical trials.
Clinical sites and institutions may also hinder fair payment, either because of internal policies or a refusal to handle the administrative aspects of payment. A federal tax and budget bill that passed in early July 2025 lowered one of these barriers recently by including a change to the tax code to raise the threshold for reporting income obtained through clinical trial participation from $600 to $2,000.
The issue of compensating participants has been drawing increasing attention, especially as the rise of patient advocacy continues to reinforce that participants are partners in the research enterprise. In time, we hope that all parties involved in clinical research will realize that ethical study conduct requires fair and reasonable compensation of participants.
Jake Eberts serves on the board of directors of the nonprofit 1Day Sooner.
Lindsay McNair is principal consultant at Equipoise Consulting.