The effect of preventive measures in reducing aftereffects to hypnosis

In the present study we assessed the efficacy of several procedures in minimizing the occurrence of aftereffects of a hypnotic induction. We gave experimental subjects (n = 347) a brief lecture dispelling some myths about hypnosis, told them no psychological treatment would be undertaken, and then administered the Harvard Group Scale of Hypnotic Susceptibility, Form A (HGSHS:A) in which all references to aftereffects had been removed. We gave the standard version of the HGSHS:A to control subjects (n = 340). Although the treatment condition did not reduce the overall incidence of effects, long-term effects were significantly reduced. Medical and psychosocial histories were obtained from subjects prior to the induction, but they proved to be of limited value in predicting sequelae. Contrary to the results of Coe & Ryken (1979), hypnosis produced more frequent sequelae than a nonhypnotic classroom experience (watching a film followed by an introductory psychology lecture) for subjects in an ad hoc control group.