There are two parts to any therapy: the part that the therapist believes is important to therapeutic outcome and ‘the other part’. The aim of this chapter is to review the concepts and evidence that suggest that, at least in some circumstances, the other part is important. This chapter begins with a history of the placebo concept, and then applies this concept to three topics: drug therapy for depression, psychotherapy and complementary medicine. The final section examines the extent to which psychological interventions have psychological and physiological benefits.

The placebo in medicine and the art of medicine

Placebo researchers can have an ambivalent attitude towards the term placebo. On the one hand, the term describes a topic of research. On the other, the term is used in a variety of different ways, and so is potentially ambiguous. Placebo is used to mean different things because the word is always used for a particular purpose. That purpose (a) has changed over time and (b) is different between groups of researchers. So an understanding of the term placebo requires an understanding of (a) when the term is being used and (b) why and by whom. Ambiguities over the term ‘non-specific’ occur for the same reasons.