Rethinking placebo in psychiatry: the range of placebo effects†

The term ‘placebo’ is used in different contexts with different meanings (Box 1). Placebo effects have been a scientific curiosity for years, regarded as deceptive therapies and tainted by associations with quackery and dishonesty. Anthropological studies of the placebo (Thompson 2010) highlight the universality of charms and ritual to produce healing effects in all cultures, suggesting an evolutionary basis to placebo-responding. Historical roots of placebo The use of the Latin word placebo dates to the 14thcentury psalm Placebo Domino (‘I shall please the Lord’), sung by mourners at funerals. In George Motherby’s New Medical Dictionary of 1785, it was defined as ‘a common place method or medicine’, and in the Hooper’s Medical Dictionary in 1811 as ‘any medicine adapted more to please than benefit the patient’ (Aronson 1999). Early uses of placebo as a control condition are recorded, although not by that name, during ‘trick trials’ of exorcism rituals in the 16th century, whereby sham holy water or religious relics were used to expose false exorcisms during the CounterReformation (Kaptchuk 2009).