All placebos aren’t created equal: the way they’re delivered can make a difference in how patients respond to the sham therapy, new research has found.
A systematic evidence review published in the Annals of Internal Medicine has found that having a clinically significant response to placebo could substantially affect outcomes in placebo-controlled trials.
The researchers used osteoarthritis of the knee as an example, reviewing 149 randomised trials comparing widely-used medicines against four placebos: oral, intra-articular, topical and oral-plus-topical, aiming to quantify the effect of differential placebo effects on active-treatment effect estimates.
They found that intra-articular and topical placebo interventions were associated with greater responses than oral placebo.
“All placebos are not equal, and some can trigger clinically relevant responses,” the authors wrote.
“Differential placebo effects can substantially alter estimates of the relative efficacies of active treatments, an important consideration for the design of clinical trials and interpretation of the results.”