Questions Surround Placebos in Large-Scale Review

Placebo-controlled studies often fail to identify what are in their placebos, according to a review published in the Annals of Internal Medicine.

Funded by a grant from the University of California (UC), Beatrice A. Golomb and fellow researchers at UC San Diego reviewed the introductions and methods sections of a reported 176 studies published in peer-reviewed medical journals-only to find out that a majority of those studies failed to disclose the compositions of their placebo treatments.

The review used studies published from January 2008 to December 2009 in four English language medical journals with “high impact factors.” Placebos used included pills (86), injections (65), and other treatments (25).

The researchers discovered that the full contents of placebo pills were only disclosed 8.2% of the time, and injections and other treatments were disclosed 26.7% of the time. Full disclosure was reported just 23% of the time.

While public knowledge of placebo makeup appears very limited from this review, this does not necessarily mean that there isn’t some documentation of placebo contents elsewhere in the publication process. Still, there is reason for concern.

“Placebos were seldom described in randomized, controlled trials of pills or capsules,” wrote the study’s author. “Because the nature of the placebo can influence trial outcomes, placebo formulation should be disclosed in reports of placebo-controlled trials.”