How placebo characteristics can influence estimates of intervention effects in trials

[Extract] Researchers now recognize the need to completely describe
active interventions within trials.1,2 However, the importance
of clearly describing placebo control interventions is
not well reported or understood. Placebo controls are interventions
used in clinical trials that do not contain the “active” components
of the active intervention. The purpose of placebo control
interventions is to provide a baseline measure of effectiveness
against which the effects of the active interventions can be measured.
Yet, placebo control interventions come in many forms,
ranging
from pills and injections to sham surgery.3–7 The placebo
control characteristics chosen by investigators have different
effects and can contribute to either an overestimation or underestimation
of the benefits or harms of the active intervention.8 Despite
this, placebo characteristics are clearly reported in fewer than 10%
of drug trials and fewer than 30% of nondrug trials.9 This failure to
report placebo characteristics presents a barrier to the interpretation
of placebo-controlled trials.