Ethical aspects of placebo groups in pain trials: lessons from psychiatry.

Placebo control use in clinical research is contentious in areas where effective treatments already exist. Determination of appropriate standards for placebo use is especially difficult in areas such as pain treatment and psychiatry, in which substantial placebo responses can occur. Debates are characterized by three common themes: (a) whether the state of existing treatments forbids placebo use, (b) whether the nature of the condition being treated and the level of additional risk permit placebo control use, and (c) whether methodological concerns are sufficient to justify placebo use. A review of these themes in the psychiatric research literature suggests possible strategies for analysis of this issue in the area of pain research.