The strength of expectation, which underpins placebo effects, decreases if people realize they are taking a placebo.

“the structure of the information given to somebody and the belief that they form about what ought to happen that is the expectation effect which you'll start to realize more and more across today's episode that expectation effect really is the underpinning of the placebo effect well the strength of that expectation is really hard to Anchor across individuals and in fact if people realize they're taking a placebo the magnitude of of the dopamine increase is actually decreased”