meta-analyses on the effectiveness of hypnosis

Kirsch, I., Montgomery, G., & Sapirstein, G. (1995). Hypnosis as an adjunct to cognitive-behavioral psychotherapy: A meta-analysis. Journal of Consulting & Clinical Psychology, 63, 214-220.

In this meta-analysis studies were considered for inclusion if hypnosis was used as an adjunct to cognitive behavioural therapy. This approach is consistent with the view that hypnosis is not a therapy in its own right, but instead can make valid forms of therapy more effective. Accordingly, studies conducted on a wide variety of patients with a range of disorders were included in the meta-analysis. Problems treated included phobia, obesity, and pain, and it is important to note that the result is therefore not specific to any one disorder. The results showed that the addition of hypnosis substantially enhanced treatment outcome, with the average client who received cognitive-behavioural hypnotherapy showing greater improvement than at least 70% of clients receiving non-hypnotic treatment. The results were particularly pronounced for studies on obesity, and effect sizes for other treatments was generally slightly lower.

Lynn, S. J., Kirsch, I., Barabasz, A., Cardeña, E., & Patterson, D. (2000).

Hypnosis as an empirically supported clinical intervention: The state of the evidence and a look to the future. International Journal of Clinical and Experimental Hypnosis, 48, 235-255.

Flammer, E., Bongartz, W. (2003). On the efficacy of hypnosis: A meta-analytic study. Contemporary Hypnosis, 20, 179-197.

Meta-analysis included the results of 57 randomised clinical trials which compared pateitns treated exclusively by hypnosis to either an untreated control group or to a group of patients treated by conventional medical procedures. A medium effect size of d=0.56 was observed indicating superiority of treatment in hypnosis groups, but this must be understood in the context of comparisons of hypnosis with no-treatment or standard-treatment. Of six studies that reported correlations between hypnotic susceptibility and outcome the average was r=0.44.

Formal research studies on hypnosis and weight loss

Bolocofsky, David N.; Spinler, Dwayne; Coulthard-Morris, Linda (1985).

Effectiveness of hypnosis as an adjunct to behavioral weight management.

Journal of Clinical Psychology, 41 (1), 35-41 109

17-67 year olds completed a behavioral treatment for weight management either with or without the addition of hypnosis. Results show that, at the end of the 9-week program, both interventions resulted in significant weight reduction. However, at 8-month and 2-year follow-ups, the hypnosis subjects showed significant additional weight loss, while those in the behavioral-treatment-only group exhibited little further change. More subjects who used hypnosis also achieved and maintained their personal weight goals.

Cochrane, Gordon; Friesen, J., (1986) Hypnotherapy in weight loss treatment

Journal of Consulting and Clinical Psychology. Volume: 54 489-492
Investigated the effects of hypnosis in weight loss for 60 females, at least 20% overweight and not involved in other treatment....hypnosis was more effective than a control group (17 vs. .5 pounds on follow-up).
Kirsch, Irving (1996).

Hypnotic enhancement of cognitive-behavioral weight loss treatments--Another meta-reanalysis.

Journal of Consulting and Clinical Psychology, 64 (3), 517-519.
Averaged across post treatment and follow-up assessment periods, the mean weight loss was 6.00 lbs. (2.72 kg) without hypnosis and 11.83 lbs. (5.37 kg) with hypnosis....At the last assessment period, the mean weight loss was 6.03 lbs. (2.74 kg) without hypnosis and 14.88 lbs. (6.75 kg) with hypnosis... Correlational analyses indicated that the benefits of hypnosis increased substantially over time