Principle O1: participation can stop, reduce or change

Everyone running or taking part in studies should be aware that participants may choose to change, reduce or stop their participation after they agree to join the study.

All language and communication about any participation changes should be clear about exactly what has changed, reduced or stopped, and what has not.

In laws and other rules about research with human participants, ‘withdrawal’ of informed consent is described in all-or-nothing terms – participants have either given consent to participate, or they have withdrawn their consent and are not taking part in any aspects of the study anymore.

In reality, things are often more complex than that.

Study participants might choose to completely stop only some aspects of study participation, for example taking study treatment, filling in study questionnaires, or attending study-specific hospital visits.

Rather than stopping participation entirely, they might instead want to reduce participation, for example taking part less often.

If it is feasible and still fits with the study’s aims, participants might also change how they take part, for example they might take part in study activities at the same times, but in a different way (for example, via telephone calls with their research nurse instead of going into a clinic for a visit).

It may even be possible for participation to increase in some cases, for example if a participant were to change their mind about stopping aspects of participation and re-start them. Again, this can only happen if it is feasible and meets the study’s aims.

It is important that everyone running and taking part in studies is aware of this complexity. We also need to use language that reflects this. Just describing study participants as ‘withdrawn’ or ‘off-study’ is unlikely to be useful in many cases, because we won’t know exactly what participants’ wishes are, or exactly what they want to stop.

See also:

Related PeRSEVERE resources:

  • This principle impact on most of our other guidance. Go to PeRSEVERE in practice to see more on the implications for how clinical trials should be designed and managed.
  • See our suggestions for terminology to use when discussing participation changes in any context.

Related PeRSEVERE principles:

  • Unless a participation change needs to happen in order to protect a study participant (usually in relation to whether or not they continue taking a study treatment), all changes in participation should be decided by the participants themselves. See principle O2.
  • See the principles about study development D1 (protecting study integrity by design) and D2 (protocol content) for more on preparing for participation changes during the study design stage. As per principle D1, any sort of reduced or alternative ways for participants to keep taking part should only be allowed if they support the scientific integrity of the study.
  • The issue of clear language and communication mentioned above affects many aspects of how studies are designed, run and reported. As well as study protocols (see principle D2), this is important in communication between researchers and study participants (see principles D3, D4 and D5), training of researchers running studies (see principle D6), data collection (principle M1), monitoring study progress (principle M2) and study reporting (R2).
  • Study protocol: this is the document (or set of documents) that describes why a study is needed, what it aims to achieve and how it should be run.
  • We use the term “running” a study here to mean all activity involved in making a study happen, including getting the relevant approvals to start the study, working with the NHS and other organisations to set up study sites where participants will be recruited, making decisions about the management of the study, collecting and processing study data, and so on.