[dragonwriter]

> I don't disagree exactly about missing a control for the placebo, but I think a control for a placebo is logically impossible, and therefore nobody has ever, or can ever, measured a placebo effect.

The control for a placebo is no intervention, and not only has placebo effect been measured, but differential placebo effects by administration method have been measured (a placebo treatment that involves piercing the skin, for instance, has a bigger effect than a pill.) This is why a valid placebo needs to match administration method of the intervention being tested.

[perl4ever]

There is no way to coherently define the "placebo effect".

When you test a treatment vs. placebo, and speculate that there is a "placebo effect", it means that you are supposing that lying about treatment produces a therapeutic effect.

But you can't test a placebo vs. nothing, because a placebo is not a treatment, and nothing is not a placebo.

Giving a sugar pill and disclosing you are giving a sugar pill is not the same thing as lying about treatment (unless the recipient believes it is efficacious). Lying about it being efficacious doesn't help your experiment unless it's a credible lie.

Giving "nothing" cannot be a control because it is obviously different from a sugar pill. So you cannot do a blind test.

The idea of testing a placebo effect is an epistemological morass.