Testing if placebos really work

Early placebo trials that tested the effects of homoeopathy tablets revealed that doing nothing was better than both homoeopathy and allopathic (standard) medicine.

In the 1990s, Danish medical researchers compared people who take placebos with people who take no treatment at all. They concluded that there is little evidence that placebos, in general, have powerful clinical effects, but the researchers made incorrect comparisons. Today it is widely accepted that placebos are effective for some things, like pain, but not for everything.