ABSTRACT
The term placebo is Latin for “I shall please.” In medical research and practice, a placebo is a treatment that is capable of making people believe it is, or could be, the real treatment when in fact it is not that treatment. A sugar pill that is indistinguishable to a patient from real vitamin C, for example, could be a placebo. Within clinical trials, placebo controls are often used as a standard against which experimental treatments are compared. For example, when evaluating a new drug, investigators can give some patients a placebo and other patients the experimental drug. If the experimental drug outperforms the placebo by a suffi cient margin, it is said to be effective. Patients (as well as, if feasible, doctors, outcome assessors, and data analysts) in these trials are often masked, which means they don’t know which treatment is the experimental drug and which is the placebo. Placebo use in clinical practice and clinical trials is both common and controversial (Howick, 2009, Howick et al., 2013a). A great deal of philosophical controversy surrounds what placebos are (Gøtzsche, 1994, Nunn, 2009), as well as whether placebos are ethical (Foddy, 2009, Howick, 2009). There is also a dispute-the one I will concern myself in this chapter-about the correct methodology that should be used to measure placebo response.
