A conditioned response model of the placebo effect predictions from the model.

A model of the placebo response as a conditioned response (CR) is presented and predictions from this model are listed. Through association with active ingredients (UCS), neutral (CS) places, persons, procedures, and things can come to acquire the ability to reduce pain, anxiety, and depressive responses. One major counterintuitive prediction from the model is that therapists who routinely use active ingredients (UCS) or powerful drugs will get stronger placebo effects than those who routinely use "inert" ingredients (CS) or weak drugs. Developmentally, placebo responding appears to involve two successive conditioning stages, which may involve first the left and later the right hemisphere in right-handed subjects. The relationship between placebo responding and hypnotizability is discussed.