Methods and Applications of Statistics in Clinical Trials, Volume 1: Concepts, Principles, Trials, and Designs

Chapter 61

Placebos

Anne Holbrook, Charles H. Goldsmith, and Mova Leung

61.1 History of Placebo

The placebo, which originates from Latin meaning “I shall please”, was used for centuries as therapy for patients whom physicians were unsure of how to treat or for whom no useful treatment was available [26]. Attitudes towards therapies in Western cultures have shifted dramatically over the last four decades. Principles of safety, efficacy, and informed consent of participants are now well entrenched (see Ethics of Randomized Trials); the randomized controlled trial (see Clinical Trials, Overview) dominates as the method for evaluating therapy and patients are increasingly involved in decisions about their care [38]. The role of the placebo has evolved in response to all of these factors. In research, the notion of placebo control arose to account for those beneficial or harmful effects not directly attributable to the therapy of interest. Despite some dissent, placebos and placebo-controlled trials remain the benchmark by which all new drugs are evaluated and regulated [50]. In clinical care, any part of an encounter can have some therapeutic value and influence the patient’s response, including taking a history, stating a diagnosis, or making repeated measurements (e.g., blood pressure) or assurances about prognosis. Knowledgeable clinicians are interested in determining which parts of the placebo effect they should implement to optimize their patients’ health.

61.2 Definitions