From Scientific American: The placebo effect works even if you are aware that you are taking sugar pills.
Patients who receive dummy pills often show clinical improvement. Placebos work, doctors believed, because the mind is a powerful thing. Just thinking you’re being treated can make you feel better. In this study, however, docs told patients they were getting placebos. Eighty patients with irritable bowel syndrome were instructed to take two sugar pills daily. The bottle even had “placebo” printed on it. After three weeks, 60 percent of the placebo group reported relief from symptoms, compared to 35 percent who’d received no treatment at all.Bottom Line: Yes, we are stupid. That's why intelligence is useless in the stock market. And that's why I would prefer not to be the human animal I am. I would like to be something else, but there is nothing else and I have to live within myself till the end.