At present, less than half of patients receiving placebo as part of a clinical trial are informed about their treatment when the trial is over, despite government recommendations to ensure that that the public have confidence in, and benefit from, quality research.
The team surveyed 107 investigators who published a placebo controlled randomised trial published in 2000 in five leading medical journals.
Over half (55%) of investigators did not inform any participant of their treatment allocation, or only informed those who asked. The main reasons for not informing participants were that the investigators never considered this option or that they wanted to avoid biasing results.
It is possible that the placebo response may be disrupted when the treatment is unmasked to patients, say the authors. For instance, a recent trial evaluating the effects of antidepressants found that when placebo responders were told that they were receiving a placebo their mood deteriorated. However, patients must be well informed to avoid negative thoughts, misconceptions, or mistrust in health professionals.
Effective and sensitive was of communicating treatment information to trial participants are required, they conclude.