Overlapping studies are a common exclusion because they create safety risk and contaminate baseline measurements.
If you want to participate in more than one study over time, the key is timing and disclosure, not secrecy.
What goes wrong with overlap
- Residual intervention effects carry into the next protocol.
- Labs and vitals shift due to the prior study.
- Schedules collide and compliance drops.
- Protocol deviations increase and the participant is removed.
A timeline habit that prevents accidental violations
- Keep a simple timeline of study dates: screening, first dose or intervention, last visit.
- Record whether the study was observational or interventional.
- Ask for the washout window before you schedule screening.
- Ask whether observational studies count toward restrictions.
Questions to ask early
- What is the washout window for prior participation?
- Do observational studies count?
- Is the restriction about any study or specific interventions?
- How far back should I disclose participation dates?