What's in placebos: who knows? Analysis of randomized, controlled trials.
BACKGROUND
No regulations govern placebo composition. The composition of placebos can influence trial outcomes and merits reporting.


OBJECTIVE
To assess how often investigators specify the composition of placebos in randomized, placebo-controlled trials.


METHODS
4 English-language general and internal medicine journals with high impact factors.


METHODS
3 reviewers screened titles and abstracts of the journals to identify randomized, placebo-controlled trials published from January 2008 to December 2009.


METHODS
Reviewers independently abstracted data from the introduction and methods sections of identified articles, recording treatment type (pill, injection, or other) and whether placebo composition was stated. Discrepancies were resolved by consensus.


RESULTS
Most studies did not disclose the composition of the study placebo. Disclosure was less common for pills than for injections and other treatments (8.2% vs. 26.7%; P = 0.002).


CONCLUSIONS
Journals with high impact factors may not be representative.


CONCLUSIONS
Placebos were seldom described in randomized, controlled trials of pills or capsules. Because the nature of the placebo can influence trial outcomes, placebo formulation should be disclosed in reports of placebo-controlled trials.
University of California, San Diego, School of Medicine, San Diego, California, USA. bgolomb@ucsd.edu
Beatrice A
BA
Golomb
Laura C
LC
Erickson
Sabrina
S
Koperski
Deanna
D
Sack
Murray
M
Enkin
Jeremy
J
Howick
D006801:Humans; D055811:Journal Impact Factor; D010919:Placebos / Q000737:chemistry*; D016032:Randomized Controlled Trials as Topic / Q000592:standards
D010919:Placebos