Presumably the placebo effect is stronger when patients do not realise they are getting placebos.
(Sorry to badger the point, it just seems so under-appreciated and misunderstood.)
In any case, I'm saying that the so-called "Placebo Effect" is activated by the patient's belief that they will heal, which is created by the "story" told and acted out by the people around them. The word "placebo" has no inherent effect, nor does the pill, it's all a kind of hypnotic suggestion that activates a somewhat mysterious ability of people to heal themselves.
The GP said, "Presumably the placebo effect is stronger when patients do not realise they are getting placebos."
This reflects a common misconception, usually born out of the "fact" that "fake pills can't cure you".
But it turns out that this "fact" in, in fact, not true. Fake pills can cure some people some of the time. This fact is as established as a fact can be, over and over again, in thousands of studies and cases.
Imagine someone with an illness and who has never heard the word "placebo" or anything about it. Maybe you two are stuck on a deserted island. The point is, you can pick up a bit of bark or shell or a pebble or something, wave your hand over it and mumble some magic words, and tell them with total conviction that it has a good chance of curing them... because it's true.
So my first point is that it doesn't directly matter whether people know they're getting a fake pill or not, it depends on what they've been led to believe about the efficacy of fake pills. Anything that lends credibility (ability to believe) to the possibility of healing for the patient can be expected to "amplify" the "effect".
My second point, which I think you're asking about, is that the whole healing is done by the "story" engendering belief which then somehow activates the patient's own ability to heal, and that this is a kind of hypnosis, or at least related to hypnosis. Because, again, there's no magic in the word "placebo" either to strengthen or weaken the "placebo effect" and "fake pills can't cure you". Right? So it has to be "all in your head".
I mean what would you call it if I told you a story and gave you a piece of candy and your illness cured itself? Is that not hypnosis?
There's a joke people tell to disparage "alternative medicine": If it works, it's just called "medicine".
My third point is that this should happen for the "Placebo Effect"! The power of theater-- of storytelling and the mind --to engage healing should form a third pillar of medicine along with Biochemistry and Surgery.
Let's say hypothetically that two patients received this 'theater treatment' - but one had an amazing actor and the other had a mediocre actor. The amazing actor convinced Patient A of the efficacy of the treatment better than Patient B.
If you believe that 'theater treatment' or the placebo effect is binary then it doesn't matter how good the actors are, and therefore they will get better at the same rate. If you believe 'theater treatment' isn't binary, then the more the person believes in the treatment, the faster their condition will improve. That's what I mean by binary vs a spectrum.
There's evidence that placebo treatments aren't binary - e.g. placebo injections work better than pills - http://journals.plos.org/plosone/article?id=10.1371/journal.....
Therefore, with reference to my original statement 'Presumably the placebo effect is stronger when patients do not realise they are getting placebos'. In both cases, the placebo effect will work, however it will work better if the theater is more convincing - and it's more convincing when they aren't told it's sugar pills.