Placebo: From Pain and Analgesia to Preferences and Products

When the placebo response was invoked by Beecher (1946, 1955) in soldiers who were wounded on the beaches of Anzio (it was noted that wounded soldiers required less morphine than wounded civilians), it unleashed a revolution in the understanding of the underlying neurobiology of the placebo effect and the impact of placebo in human clinical studies. Although placebo is a widespread phenomenon in medicine, the underlying neurobiology of it is not yet fully elucidated, though pain and analgesia have provided the most compelling and mechanistic insights into the phenomenon (Amanzio and Benedetti 1999; Beecher 1955; Benedetti et al. 2003; Fields 1981; Gracely et al. 1983; Levine, Gordon, and Fields 1978; Levine et al. 1979; Petrovic et al. 2002). Recent neuroimaging studies in humans provide supporting and novel insights into the central nervous system's processing of the placebo response (Ploghaus et al. 2003; Wager et al. 2004). Placebo is defined as an inactive substance that is used in controlled studies to determine the effectiveness of medications. However, if Shiv, Carmon, and Ariely's (2005) results indeed reflect a placebo response, this definition is probably outmoded because it should include nonmedical effects.