If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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Sure. But the question under discussion here is what actually is the placebo effect and how much of it can you attribute to psychosomatic factors and how much to just regression to the mean (aka natural healing).
You are correct in that most intervention studies don't care about the magnitude of the placebo effect, they just take the placebo arm of the trial as a baseline. But that doesn't mean that we couldn't or shouldn't ask questions about the placebo effect itself.
In that case your opener is slightly polemical :)
Agreed. The problem with nonintervention arms for studying the placebo effect is that there aren't clear incentives for adding them and they cost statistical power.