[Placebos: aspects in medical history and approaches to definition]

The historic roots of the term placebo, its development from religious to secular use and finally its establishment as a medical terminus at the end of the 18th century are described. After the first and rare placebo publications in the 30ties and 40ties a sudden increase in the number of published placebo articles took place since 1950. In the following decades the progress in experimental placebo investigations was overwhelming and placebo phenomena more and more became a subject of scientific inquiry in its own. An overview of the experimental results of this period concerning the efficacy and toxicity of placebo interventions is given. Existing attitudes and prejudices to placebos are confronted with hard data from empirical studies. In particular the 'myth of the non-specificity of placebos' will be critical reviewed and reconsidered. Finally, after a short retrospective view to placebo definitions in medical dictionaries since the 19th century the actual controversy between pharmacological and general placebo definitions is outlined. Two modern definitory propositions of Shapiro and Morris, 1978, and Brody, 1980, are presented and discussed in detail.