Hypnosis: placebo or nonplacebo?
According to Grünbaum's definition of placebo, a therapeutic procedure can be considered a nonplacebo if it can be demonstrated that its effects are produced according to the theory upon which the therapy is based. If the theory is adopted that hypnotic effects depend upon mobilization of the patient's hypnotizability, which is a measurable characteristic, a testable theory is provided. Experimental literature is reviewed that shows that placebo effects are not related to hypnotizability. Clinical outcome studies make it clear that results of hypnotherapy are related to hypnotizability in some disorders such as pain and anxiety, but not in the treatment of addiction or habit disorders. An example of a procedure is given in which hypnosis is nonetheless usefully applied for its placebo value as a method to generate positive expectancies.