I am very much not convinced of the interpretation of the placebo effect as "the fact that just thinking that you're getting some treatment of benefit can have actual benefits." The placebo (and corresponding nocebo) effect is completely intuitive when you think of it as a measurement artifact. It's strongest in self-reported outcomes, it goes away or is massively reduced the better your blinding - all exactly what you'd expect from a combination of confirmation bias and expectations (both on the part of the person receiving the treatment and doing the study).
Even to the extent that there are placebo effects in clearly quantifiable outcomes (e.g. blood pressure, etc) it's still way more plausible that these are due to nonspecific treatment effects (e.g. taking a pill every day for your blood pressure reminds you of your problem with blood pressure and so you take the stairs instead of the elevator or you don't have a second serving of steak) than that there's a way for your mind to just cause arbitrary positive or negative effects above and beyond your normal immune system - but only if it's tricked into it.
There are brain imaging studies that show the placebo effect in action for depression and pain. Also, given what we know about psychological stress causing symptoms such as headaches, pain, diarrhea, etc. I think it would be impossible for the placebo effect not to have "actual benefits".
It's reduced by blinding because both groups think they're getting treatment - that is, they both get the placebo effect, and the test group also gets the benefit of the actual treatment.
Edit: It's not really reduced by blinding, it's removed as a variable because both groups have the placebo effect.
I suppose the fact that it's reduced by blinding the patient is a wash (consistent with both theses), but now you need to add two new causes to explain why single and double blinding work, whereas none of the observed phenomena are inconsistent with other well-known research biases.
Single blinding spreads the placebo effect to both groups since both groups think they're getting the treatment.
Double blinding reduces the placebo effect, since the researcher can't imply to the patient which treatment is actually real and which is placebo since they don't know.
Extending this a bit further, I think this applies to things like cars or cosmetics or fashion or wine. Pretty much any consumer good actually.
I remember a study (might be from the Ariely book) where they took wine from the same bottle, put it into two decanters, and said one was way more expensive than the other. People were asked their impressions of the two wines. The more expensive wine received rave reviews while the supposedly cheaper one was marked only passable.
Interesting on one level, sad on another. And exploitable for profit, as some smart marketers have been doing for a while.
It applies for computer services as well. You're more likely to be abused by your clients (blamed for problems unrelated to you, called at odd hours of the night for no good reason, yelled at, etc.) or fired in favor of somebody else if you give them your services for cheap or free than if you charge a lot.
Speaking of expensive placebos, how is selling oscillococcinum legal? I can't imagine how many well-intended people mistakenly buy these sugar pills believing it is efficacious medicine.
Lots of people do know that homeopathic means it is just water. They believe there is an imprint of the molecule left in the water. Some believe the imprint works as well as the original molecule. Others believe that imprint is how the molecule actually works, so getting rid of the molecule is healthier.
I'll tell you how i bought it in 2005. My boss's wife recommended it to me so i went out and got it. Then my symptoms went away and i thought OK i should do that again.
I trusted the recommendation and presumed the pharmacy wouldn't be selling actual sugar pills so I didn't investigate it at first. Then when I saw it labeled with the homeopaths a year later somewhere else, I looked into it and was like "oh...".
I think my experience is probably 97% of the stories with or without the realization. The other 3 percent is like " oh homeopaths, gee isn't this stuff great? What a wonderful science."
Stuff like this is why I never buy or take any medicine until I know what's in it and do some brief research to see how it works and what effects it might have.
Well, emphasis on the "just." When I say "this is just water" I mean nothing but, no imprints, no magic whatever, just plain water. I'm sure plenty of people "understand" it as you say, but it's not what I meant to include.
Even to the extent that there are placebo effects in clearly quantifiable outcomes (e.g. blood pressure, etc) it's still way more plausible that these are due to nonspecific treatment effects (e.g. taking a pill every day for your blood pressure reminds you of your problem with blood pressure and so you take the stairs instead of the elevator or you don't have a second serving of steak) than that there's a way for your mind to just cause arbitrary positive or negative effects above and beyond your normal immune system - but only if it's tricked into it.