Relevant participants

Consider the relevance of research in laboratories, animals, or highly selected people.

When deciding about a health action, the best information comes from comparisons of health actions that have included people like those who will be affected by the decision. Often there are only comparisons done on selected people or animals, and it is very uncertain what the effects of the treatments are in the people for whom a decision is being made.


Studies that are done in test tubes, only include animals, or only a selected group of people, may not provide results that are relevant to most people.

New treatments (health actions) are often first tested on healthy people, not people with the health problem that the treatment is designed to help. The findings from those studies are often misleading.

Studies on animals are sometimes used to test drugs and other treatments before studying their effects in humans. However, many animal studies fail to predict benefits or harms in humans because:

  • These studies use treatments, animals, or outcome measures that are poorly matched to people – for example, studying a short-term disease in animals as the basis for drawing conclusions about a long-term health problem in humans.
  • The causes and effects of the health problem in humans are not the same as in animals.
  • The animal studies may be poorly designed and conducted.
  • Animal studies are varied and unpredictable in how good they are for predicting successful treatments in humans.


News reports often make misleading conclusions based on findings from studies on animals or an unrepresentative selected group of people. Based on a study in mice of a chemical found in vegetables like broccoli, cabbage and kale, news reports falsely claimed that “broccoli slows arthritis” in humans. Another news report claimed that a treatment “could treat phobias and perhaps even post-traumatic stress disorders” based on a before-and-after study in 15 healthy volunteers without any phobias.

Remember: Results of comparisons of health actions in animals, highly selected groups of people, or people that are very different from those who will be affected by a decision may be misleading.

Back to Top