Study design
Placebo
An inactive comparison designed to look or feel like the intervention being tested.
What it means
Definition
Placebo. A placebo helps separate the specific effect of an intervention from expectation, attention and natural symptom variation. Placebo controls are most important when outcomes are subjective.
What it can tell you
It can show how close the evidence is to a real human health outcome.
What it cannot tell you
It cannot prove that a treatment works in people unless human outcome data are available.
Headline trap
Why this matters in headlines
A pain study without a placebo may struggle to separate drug effect from expectation.