A patient can clear every eligibility criterion, live ten minutes from the site, and still say no. When that happens, the reason is rarely on the checklist. It's one of six frictions that decide whether a patient can consent, and mean it. None of them are about the science. All of them are addressable.
They don't trust it
Trust friction is when a patient doesn't trust the care team, the sponsor, or clinical research itself. It's often shaped by community history and personal experience of discrimination, and it runs deepest in populations that carry a documented history of research harm. The willingness is usually there: CISCRP's 2023 survey found 87% of people would be willing to join a trial, but only about a third trust the industry running them. That gap shows up as underrepresentation, with only 23% of 2023 pivotal trials representatively enrolling Black participants and 30% Hispanic participants.
PRISM reads it across three models: trust in the care team, trust in research itself, and an optional, consented experience-of-discrimination signal. A patient can trust their own physician completely and still not trust research, and the fix for each is different. The response is never to screen distrustful patients out. It's to earn the trust: stories from named peers and trusted figures, transparent disclosure of how the trial actually works, and honest acknowledgement of past harms where they're relevant to the population.
They can't follow it
Comprehension friction is when a patient can't read the materials, follow the medical content, interpret the risk numbers, or make sense of the consent form and the protocol. This is not a fringe case. The National Assessment of Adult Literacy found that 36% of US adults, more than 75 million people, have only basic or below-basic health literacy. Meanwhile, a landmark analysis in the New England Journal of Medicine found consent forms averaging around a 10.6 grade reading level, well above the 6th-to-8th-grade level the FDA and NIH recommend. The most common consent failure isn't refusal; it's a signature on a document the patient didn't fully understand.
PRISM reads it across six models spanning general literacy, health literacy, numeracy and risk comprehension, consent-form readability match, protocol-complexity match, and education as context. It compares the form to the patient, not the form in isolation. The response is to meet the patient where they read: plain-language education matched to their level, visual and audio alternatives, teach-back comprehension checks, and a simplified consent summary.
The trial is too much on top of everything else
Cognitive load friction is different from comprehension. A patient with perfectly adequate literacy can still be overloaded, because complexity, life stress, and the daily work of managing a chronic disease have already consumed the mental capacity a trial needs. Understanding the material and having the bandwidth to act on it are two separate things.
PRISM captures it directly, reading response times, abandonment, repeated clarifications, self-reported stress, and the complexity of the patient's existing regimen. The response is to lighten the load: chunk the protocol information, pace decisions one at a time, strip out the extraneous, and design against decision fatigue at the consent moment.
The decision doesn't feel settled
Decision confidence friction is when a patient feels uncertain, pressured, or conflicted at the consent moment even when fully informed. The form is understood. The choice just doesn't feel resolved. Decisional conflict predicts later regret and withdrawal, and it's invisible on paper, because an unsettled patient signs exactly the same way a confident one does.
PRISM reads it across decision confidence, treatment preference strength, and tolerance for uncertainty, using the Ottawa Decisional Conflict short form before consent alongside behavior at the consent moment. The response gives the decision room: a decision aid that pairs values clarification with a side-by-side comparison of options, a peer testimonial of the decision process, and a genuine time-to-think and re-engagement window.
They don't see what's in it for them
Motivation friction is when a patient lacks personal belief that they'll benefit, autonomy in the decision, or the self-confidence to follow through. It's distinct from trust: a patient can trust the team completely and still not see the payoff. Expected personal benefit is the single strongest patient-side predictor of enrollment, and when a patient can't see one, altruism rarely carries them to consent.
PRISM reads it across eight models, including expected personal benefit, decision autonomy, self-confidence, stated and goal commitment, information-seeking, social influence, and perceived disease severity. The response speaks to the person: a personal-benefit narrative tailored to their stated hopes, autonomy-supportive messaging that keeps the decision theirs, goal-setting with progress reflection, and peer endorsement.
Something they feel is in the way
Emotional and mood friction is when current anxiety, depression, condition-specific stigma, or fear blocks engagement. The most sensitive disclosures live here, and they have to be handled with care. Active symptoms predict dropout whether or not they've ever been formally diagnosed, and stigma can make a patient unwilling to be visibly enrolled at all.
PRISM reads it across four models, two of them disclosure-only by design: anxiety and depression burden, and disease-specific stigma, asked with explicit consent and skip-logic and never inferred from demographics. The response is supportive rather than exclusionary: mental-health resource referral, peer-coach reassurance, coping resources, and privacy-protective participation patterns for high-stigma conditions.
Seen early, none of these is a closed door
The reason to measure the barriers to saying yes is not to predict who will decline. It's to change the conversation before they do. A trust gap becomes a reason to bring in a trusted peer. A comprehension mismatch becomes a plain-language summary. An unsettled decision becomes a second conversation instead of a lost patient. That's the difference between a consent process that collects signatures and one that builds committed participants.
Sources and methodology.
This article synthesizes published research and public benchmarks with Jumo Health's PRISM readiness framework. Statistics are presented with their publication context; trial conditions and patient populations vary.
- Tufts Center for the Study of Drug Development, site enrollment performance benchmarks. View source
- CISCRP, 2023 Perceptions and Insights Study. View source
- Communications Medicine (Nature), 2025, trial representativeness of FDA-approved drugs. View source
- National Assessment of Adult Literacy (NAAL), US Dept. of Education / NCES. View source
- Paasche-Orlow et al., New England Journal of Medicine, 2003, consent form readability. View source
- Johns Hopkins Medicine IRB, informed consent readability guidance. View source
- Journal of Clinical Oncology (ASCO), 2022, travel distance in early-phase trials. View source
- Geographic access to NCI-funded cancer research sites (PMC). View source
- Patient-reported out-of-pocket costs in early-phase oncology trials (PMC). View source
- Pew Research Center, Internet/Broadband Fact Sheet. View source
- FCC, Broadband Progress Report (100/20 Mbps standard). View source
- Kogan et al., Psycho-Oncology, 2022, caregiver role in phase 1 trial decisions. View source
- Cerutti et al., Cancer Medicine, 2025, family system and trial retention. View source
- Tufts Center for the Study of Drug Development, protocol amendment benchmarks. View source
- Trials (Springer), 2025, retention and missing primary-outcome data review. View source
- US FDA, Diversity Action Plans (FDORA 2022). View source
