In clinical trials, a sham is a procedure or device that looks the same and feels the same as an active treatment being tested but doesn’t actually do anything. It’s used as a control to compare the effectiveness of the active treatment with no treatment at all.
A placebo, on the other hand, is a dummy pill or other inactive substance that looks the same and feels the same as the active treatment being tested but has no therapeutic effect. It’s used to determine if any observed effects are due to the specific active ingredient(s) in the drug, rather than just the psychological effects of taking a pill.
The sham and placebo are different concept.