Development of a model for the conduct of randomized clinical trials of hypnotic intervention.
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Research on the efficacy of hypnosis has been limited due to the lack of a sham hypnosis (placebo) for comparison to use as a control in randomized clinical trials. Instead, researchers have had to use a variety of controls, resulting in inconsistency that greatly limits researchers’ methodology and makes it difficult to compare study results or make aggregate statements regarding hypnosis’ efficacy. This study consisted of three primary aims: 1) to evaluate whether white noise can be considered an "inert" procedure; 2) to evaluate the credibility of a model of sham hypnosis that uses white noise as a potential form of "hypnosis" when presented within the hypnotic context; and 3) to explore the relationships between participant characteristics and specific outcome measures. Seventy-five undergraduate students were randomized to one of three groups: hypnosis; sham (white noise presented in the context of hypnosis); or control (white noise in the absence of hypnotic context). Measures of interest involved participants’ ratings of: 1) therapist’s professionalism; 2) the consistency of the environment with hypnosis; 3) subjects’ perception that they received hypnosis; 4) subjects' evaluation of the procedure as pleasant, relaxing, and beneficial 5) participants' perceived acceptability (evaluated by assessing perception of the procedure as acceptable, ethical, effective, of the procedure they received; and 6) shifts in relaxation resulting from each procedure. In each of the variables of interest, subjects who received sham hypnosis and those who received a hypnotic induction demonstrated significant differences from those assigned to the white noise control, with effect sizes ranging from .165 to .852. However, there were no significant differences between participants' ratings of the sham and hypnosis procedure in any of these domains. Taken together, results support the feasibility of using white noise as an inert procedure that, given the proper environmental context, can serve as a credible sham hypnosis.