Hypnosis and the Alleviation of Clinical Pain: A Comprehensive Meta-Analysis.

This is the first comprehensive meta-analysis in approximately 20 years of all controlled studies of the use of hypnosis for relieving clinical pain. To be included, studies were required to utilize a between-subjects or mixed model design in which a hypnosis intervention was compared with a control condition in alleviating any form of clinical pain. Of 523 records screened, 42 studies incorporating 45 trials of hypnosis met the inclusion criteria. Our most conservative estimates of the impact of hypnosis on pain yielded mean weighted effect sizes of 0.60 (p ≤ .001) for 40 post trials and 0.61 (p ≤ .001) for 9 follow-up trials. These effect sizes fall in the medium range according to Cohen's guideline and suggest the average participant receiving hypnosis reduced pain more than about 73% of control participants. Hypnosis was moderated by the overall methodological quality of trials-the mean weighted effect size of the 19 post trials without high risk ratings on any of the Cochrane Risk of Bias dimensions was 0.77 (p ≤ .001). Hypnosis was also moderated by hypnotic suggestibility, with 6 post trials producing a mean weighted effect size of r = 0.53 (p ≤ .001). Our findings strengthen the assertion that hypnosis is a very efficacious intervention for alleviating clinical pain.