Welcome back to "Doggerel," where I ramble on about words and phrases that are misused, abused, or just plain meaningless.
One of the funniest arguments I've heard from woos is that their magic pills work through the placebo effect, and I don't think they mean it in a Zen "acting by not acting" sort of way.
The placebo effect is what you get when you do nothing, but think you're doing something: It's a combination of two things: Psychological tricks and coincidental recovery.
First, are the psychological tricks: Confirmation bias, the regressive fallacy, misattribution, subjective validation, and so on and so forth: We essentially fool ourselves into thinking the symptoms aren't as bad, or not as common, etcetera. They're still there, but we have an excuse to ignore them: They don't fit with expectations, so we rationalize them away. There's no "power of positive thinking" going on, just a conscious and unconscious motivation to ignore what doesn't fit. This is why double-blinding is important: It make most of those rationalizations very implausible, and points of view irrelevant: Belief isn't going to change the numbers.
Second, there is the physical aspect: Natural improvement and coincidental recovery. It could be that a person's immune system is rallying for a final assault when he takes the treatment. There's no way to be certain that it's the drug that's doing anything. That's where the placebo control in studies comes in: Compare the drug to essentially doing nothing as a base line. If there's a significant difference between the placebo group and the treatment group, it's unlikely to be coincidence. The bigger the study, the less likely coincidences become.
There are probably more aspects to placebos and nocebos, but that should be the bulk of it: The placebo effect is what happens when you merely think you're doing something.