By Dr. Brian McDonough

In the world of medical studies, one way to determine whether a new treatment works is to compare it in a randomized controlled trial to a placebo.

Placebos are substances with no known activity against the health condition of interest. There are no rules in place telling doctors what the makeup of a placebo has to be but if you think about it, the composition of placebos could influence study results if the substance thought to be inactive actually had some activity against the disease.

Researchers reviewed 176 published randomized controlled trials to evaluate how frequently the studies described placebo composition. In total, the researchers reviewed 86 studies of pills, 65 studies of injections, and 25 studies of other treatment methods. The researchers focused on four influential journals: The New England Journal of Medicine, JAMA, The Lancet, and Annals of Internal Medicine.

The researchers said it is extremely rare to know what placebo is being used.

Reported By: Dr. Brian McDonough, KYW Newsradio Medical Editor

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