To the Editor.
—The issue of bias was not raised in the otherwise excellent article by Dr Turner and colleagues1 on placebo effects. The point is that the placebo arm of a trial is particularly vulnerable to specific types of bias.In clinical trials, as opposed to regular patient care, patients are generally highly compliant and have a good feeling about the trial because they think it will provide something from which they can benefit. They also do not want to disappoint the investigators who have taken so much interest in them. This wish not to disappoint may produce an enhanced placebo effect on the part of the participants. Investigators, on the other hand, may find it difficult or impossible to tell the complete truth about the dummy2 and usually exaggerate the potential of the trial. Furthermore, many phase IV trials do not include a written informed consent
Cleophas TJM. The Importance of Placebo Effects. JAMA. 1995;273(4):283. doi:10.1001/jama.1995.03520280027021