Behavioral Science in Clinical Trials: Part 1 — Why Recruitment Problems Start Before Recruitment

Recruiting patients into clinical trials has become one of the biggest bottlenecks in drug development, and one of the most expensive.

Many challenges in clinical trials typically arise during the recruitment phase, but the root causes often originate earlier in the process. Decisions made during trial design phase and the study startup phase can undermine a trial before the first participant is even approached. By the time recruitment starts, the desired outcome of fast recruitment and retention is already compromised.

In this — the first of a three-part series on applying behavioral science and service design to improve clinical trials — we examine the sources of recruitment challenges, suggest ways to identify them earlier in the process, and discuss how behavioral science can help trials recruit more quickly, reach diverse populations, and avoid costly delays.

The challenges pharma faces in recruiting patients for clinical trials

The two main challenges that pharma companies face when recruiting patients for clinical trials are, first, that the speed of recruitment is rarely fast enough, and second, that some trials never reach full enrollment.

Both challenges pose significant roadblocks for pharma. If patient recruitment is slow, it leads to costly delays in completing the trial, ultimately postponing the timeline to bring the drug to market. Furthermore, if they are unable to recruit enough patients, they won’t obtain the necessary data to investigate the drug’s effectiveness, preventing its launch.

While the recruitment phase is often blamed for the issues described above, many of the problems that appear at this stage actually stem from earlier bottlenecks. These occur when protocol design decisions are made that are impractical and, in some cases, completely unfeasible for real patients and clinicians.

Factors that need to be dealt with in the trial design and study start-up phase, such as overly restrictive eligibility criteria for patient enrollment, and ensuring the selected sites have the capacity, staff, equipment, and willingness to take them on, and most importantly, designing patient and clinician-centered, more realistic trials from the start, can all have a dramatic impact on recruitment timelines.

Examining the root causes earlier in the process — and how to address them

Trial design

A common mistake pharma companies make in trial design is creating clinical trial protocols without involving the people who will actually follow them: real clinicians who will be tasked with delivering the trial in the healthcare setting. Often, the protocol is a brilliant academic and scientific concept, but it doesn’t match real-world practicalities of healthcare delivery.

To avoid this, teams should apply behavioral science research, user experience research, and service design, to design a protocol that makes sense in the real world, and to diagnose and resolve potential barriers during trial design phase for example:

• How might the inclusion of an invasive biopsy procedure in the eligibility criteria impact patient interest in the study?
• Is it feasible for investigators to schedule patient appointments at 7 am, allowing patients to attend before their work commitments?
• Could offering childcare compensation enhance the feasibility of participation for patients? If so, what would be the best approach to implement this support?
• What are some of the potential barriers patients might face during their experience in this trial, and how can we proactively provide services to address these challenges?
• What are the true motivators for the investigators to enroll patients in this trial and how can we leverage it in the way we design the trial and communicate information about it?

By investing in this type of research early, pharma teams can adjust protocol elements before they become fixed, leading to trials that work not just on paper, but in the real world.

Study startup

The study startup phase is fundamentally about selecting the right clinics and sites to run the trial, but many feasibility assessments fall short because they focus on the wrong questions. Teams tend to focus on superficial, marketing-style questions such as:

• Where is the site located?
• How many years of experience does the doctor have?

However, more substantial research and more practical, behavioral science and service design informed questions would dramatically improve this stage, such as:

• Is the clinic open early enough for working patients so that the trial can fit into their everyday life?
• Is the clinic within a reasonable distance to the patient population so they can feasibly attend the clinic as required?
• Are coordinators at the site already overloaded, or do they have the capacity to take on another trial and conduct the necessary screening of patients onto the trial?

Additionally, the startup process at sites is often hindered by operational inefficiencies that cause significant delays. Workflows tend to be manual and disjointed, and sites are often required to undergo training on software they already use. As a result, clinics may become frustrated, killing their motivation to run a trial before they have even started to enroll patients, or they may simply lack the capacity to do so due to the lengthy, cumbersome procedures.

Again, meaningful research with site staff, observing their real-life workflows, rather than relying on assumptions, can uncover these pain points that are often invisible from the sponsor side. Co-design sessions with coordinators, investigators, and study teams create tools and processes that align with how people actually work, increasing adoption and reducing friction and barriers. Ultimately, designing the process around real human behavior from the outset rather than idealized procedures, site startup becomes significantly more efficient.

How behavioral science can identify and address patient pain points early in trial planning

Conducting research grounded in behavioral science directly with patients helps uncover the real motivators and barriers to participating in clinical trials. These barriers can include fear, trust, cognitive load, social influences, lack of representation, or even whether a physician discusses trials at all.

Once these barriers are identified and understood, they should be systematically mapped to proven behavioral strategies such as trust-building interventions, reframing messages, simplifying complex instructions or processes, or removing practical burdens that create friction.

The insights gained from this research can inform many aspects of trial design, including consent forms, recruitment materials, and communication strategies, even design and delivery of procedures that could only be amended before the protocol is finalized. It is also important to ensure true co-design takes place, where patients and site staff can influence decisions before they are finalized. Co-design sessions help uncover high-risk moments so they can be redesigned early rather than after recruitment stalls.

Audience segmentation also becomes critical, particularly for the “movable middle” — people who are not inherently pro-trial but not firmly opposed, a group that often includes underrepresented populations. Since these communities face unique barriers — rural access limits, mistrust, misconceptions, or clinicians who don’t mention trials — behavioral science provides the structure to understand why past efforts failed and to build more effective, culturally attuned approaches that improve reach and participation.

Conclusion

It’s never too late to apply behavioral science, and service design to help clinical trials recruit more diverse patients faster. Whether at design, site startup, or in the middle of a stalled recruitment phase, behavioral science can uncover real barriers and help teams get unstuck. Traditional fixes like sending more emails, adding more recruitment materials, or pressuring sites rarely work because they don’t address the underlying behavioral barriers. Behavioral science, by contrast, diagnoses the true drivers of hesitation, drop-off, and disengagement, allowing teams to target solutions precisely where they matter.

Trials designed with human behavior in mind and behavioral science strategies in hand are far more likely to start smoothly and complete on time. And importantly, co-designing with patients and site staff is not an extra step or a delay but a safeguard against far bigger delays later. When the people most affected by the trial have a voice in shaping it, the result is not only a faster study but a more humane and inclusive one.

Olga Elizarova, DDS, MPH, MBA, senior consultant behavioral science, S3 Connected Health