Therapeutic effect of placebo

Townsend Letter for Doctors and Patients,  Jan, 2005  by Robert A. Anderson

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Placebos can be physical (e.g., a manipulation), pharmacological (e.g., a pill) or psychological (e.g., a conversation). Thirty-two trials were reviewed, involving results of no treatment versus pharmacological, manipulative or psychological placebo interventions. Compared with no treatment, relative risk of an unwanted outcome with placebo was 0.95 (NS). For trials with continuous outcomes, RR of an unexpected beneficial outcome in placebo was--0.28 (95% CI--0.38 to--0.19); this effect decreased with increasing sample size. The pooled standardized mean difference was--0.36 for trials with subjective outcomes (95% CI--0.47 to--0.25) but not for objective outcomes. In 27 trials involving pain treatment placebo had a beneficial effect of--0.27 (95% CI--0.40 to--0.15), with a reduction in pain intensity of 6.5 mm on a 100-mm visual-analogue scale. The authors found "little evidence in general" that placebos had powerful clinical effects. The authors state "outside the setting of clinical trials, there is no justification for the use of placebos."

Hrobjartsson A, Gotzsche PC. Is the placebo powerless? An analysis of clinical trials comparing placebo with no treatment. N Engl J Med 2001 May 24; 344(21):1594-602

COMMENT: Not all authors in the field agree that placebo effects are real. In this meta-analysis, the authors, in spite of denigrating the general effect of placebo, conclude that pain intensity was significantly statistically reduced, a result which would seem to be at odds with their general conclusion. This appears to ignore the fact that there is an inevitable placebo effect in every health professional-patient transaction. Since placebo effects are imbedded in every physician-patient interaction, it would be helpful to understand them and utilize them for better outcomes.

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