A Placebo the Patient Believes in is Effective for the Common Cold

Abstract & Commentary

By Joseph E. Scherger, MD, MPH, Vice President, Primary Care, Eisenhower Medical Center; Clinical Professor, Keck School of Medicine, University of Southern California. Dr. Scherger reports no financial relationships relevant to this field of study.

Synopsis: A randomized, controlled trial of persons with new onset common cold showed modest effects of placebo on duration and severity of the cold symptoms, but greater effects among the patients who believe in the benefits of echinacea, whether receiving the supplement or placebo.

Source: Barrett B, et al. Placebo effects and the common cold: A randomized controlled trial. Ann Fam Med 2011;9:312-322.

There is a long history of research on the power of the placebo. The authors of this article cite a 1955 paper by Beecher, "The Powerful Placebo," that looked at 15 studies involving more than 1000 patients. Beecher famously claimed that the "placebo effect" was 35.2% in many conditions.1 In subsequent research, the evidence of placebo effects is strongest for pain and depression.2,3 For the common cold, Eccles reported that a review of clinical trials on the effects of cough medications demonstrates that 85% of the reduction in cough comes from the placebo effect and only 15% from the active ingredient.4

This study was done by a team at the University of Wisconsin active in research in integrative medicine. The study was funded by the National Center for Complementary and Alternative Medicine at the National Institutes of Health. A total of 719 persons with new onset common cold, aged 12 to 80, were randomized into four groups: those receiving no pills; those blinded to placebo; those blinded to echinacea; and those given open-label echinacea. Then mean duration of the cold was 7.03 days in the no pill group. The three groups receiving pills had a reduction in cold symptoms by an average of about ½ day, and a reduction in severity of symptoms of 10-20%. Interestingly, and contrary to the hypothesis of the investigators, those receiving open-label echinacea did not have any greater benefit than those who were blinded. However, among the 120 persons who reported a belief that echinacea was effective, their illness duration was 2.58 days shorter with 26% less severity than the rest of the participants, whether they received open-label echinacea or placebo.


Belief in a therapy is a powerful therapeutic agent. We should be careful not to dispel our patient's beliefs, especially when these beliefs are not harmful. Beliefs in treatments for the common cold are widespread, including alleged benefits of echinacea, Airborne, and zinc. These treatments have been shown to be largely a placebo; however some people swear they work, and with this belief, they do!

This study was designed in 2002 at a time when there was widespread belief and some clinical evidence in the effectiveness of echinacea for the common cold. Then came four highly publicized negative clinical trials of echinacea and the study team noticed a change in belief among the study participants in echinacea during the four years of recruiting and randomizing patients. They suggest that this may have caused the modest effects of the open-label echinacea seen in the results.

As physicians, our job is to help our patients. When they are sick, we do what we can to help them get better. Our job is not to lecture patients on what the current clinical evidence is for any given treatment, a changing knowledge base anyway, when such information is not helpful in treating the patient. I do not recommend my patients spend their money on placebos they have no belief in. I do not promote unscientific beliefs. However, when patients express that they will go out and get echinacea for their cold since it always works for them, I say fine. This study shows that the patients are right, and that their belief is the therapeutic agent.


1. Beecher HK. The powerful placebo. JAMA 1955;159: 1602-1606.

2. Hoffman GA, et al. Pain and the placebo: What have we learned? Perspect Biol Med 2005;48:248-265.

3. Walsh BT, et al. Placebo response in studies of major depression: Variable, substantial, and growing. JAMA 2002;287:1840-1847.

4. Eccles R. The powerful placebo in cough studies? Pulm Pharmacol Ther 2002;15:303-308.