Abstract
The main current application of placebo is in clinical research. The term placebo effect refers to diverse non-specific, desired or non-desired effects of substances or procedures and interactions between patient and therapist. Unpredictability of the placebo effect necessitates placebo-controlled designs for most trials. Therapeutic and diagnostic use of placebo is ethically acceptable only in few well-defined cases. While "therapeutic" application of placebo almost invariably implies deception, this is not the case for its use in research. Conflicts may exist between the therapist's Hippocratic and scientific obligations. The authors provide examples in neuropsychiatry, illustrating that objective scientific data and well-considered guidelines may solve the ethical dilemma. Placebo control might even be considered an ethical obligation but some provisos should be kept in mind: (a) no adequate therapy for the disease should exist and/or (presumed) active therapy should have serious side-effects; (b) placebo treatment should not last too long; (c) placebo treatment should not inflict unacceptable risks, and (d) the experimental subject should be adequately informed and informed consent given.