[Placebo use in clinical studies].

Placebo use in clinical settings was first reported in the 1930's. Placebo-controlled randomized trials are conducted in order to explore the efficacy of new treatments. Nevertheless, the ethical aspects of placebo use remain controversial. It is usually accepted that placebo should be used only in circumstances where it causes no significant discomfort. Yet, the term "significant discomfort" may be interpreted in different ways. There is evidence that the placebo may be effective in some settings, and in other circumstances may be associated with side effects. Herein, we discuss the ethical dilemmas of placebo use, the evidence for its benefit or lack of benefit, and the current guidelines for conducting placebo-controlled trials.