What Research Shows About the Size and Reliability of Placebo

In one study of 162 patients, 55% responded inconsistently to placebo, 29% never responded and only 16% responded consistently. Telling responders from non-responders required intensive psychological testing. Another study found sham surgery and sham acupuncture produced larger placebo effects than placebo pills, likely because of the contextual factors around more invasive treatments. Those same contextual factors are present in any intervention, including exercise. The speaker describes an asthma study comparing medication, placebo, sham acupuncture and no treatment. Subjective improvement was similar across the three active arms, but only real medication improved objective measures. Patients should get better, not only feel better. Systematic reviews, including one in the New England Journal of Medicine and a Cochrane review, found little evidence of powerful placebo effects beyond patient-reported outcomes such as pain, which are hard to separate from reporting bias. Many factors driving placebo, such as what others tell the patient, are beyond the therapist's control.