Sham versus Placebo: Implications for Interpreting Randomized Controlled Trials

[Epidemiologic Inquiry 2006, 1: 14]

Clinical investigators have often naively touted any trial to be the absolute truth, giving the randomized controlled design precedence over observational studies. However, in a recent issue of the BMJ, it was discovered that the type of control method used can significantly impact the interpretation of a randomized trial result.

By comparing a sham acupuncture procedure versus an inert placebo on physical function, the investigators discovered that the two "control" methods yielded different functional results and different rates of adverse effects. Obviously the psychosocial placebo effect is much different depending on the method of control. This has implications for interpreting other randomized trials which use different intervention for controls (such as: placebo, general advice, normal behavior, alternative diet, etc), which may elicit a different confluence of adaptive factors (also known as "canalization").

Thus, are randomized trials truly interpretable as the absolute gold standard? What other limitations are there? (to be continued).

Sham device v inert pill: randomised controlled trial of two placebo treatments.
Kaptchuk TJ, Stason WB, Davis RB, Legedza AR, Schnyer RN, Kerr CE, Stone DA, Nam BH, Kirsch I, Goldman RH.
BMJ. 2006 Feb 1; EPUB