Studies show placebos are twice as effective as they were 25 years ago.
Taking a placebo can powerfully improve some people's health.
Antidepressant medication is getting more effective. But the placebos they are compared to in testing are also getting more effective.
From 2001 to 2006, the percentage of new products cut from development after Phase II clinical trials, when drugs are first tested against placebo, rose by 20 percent.
The failure rate in more extensive Phase III trials increased by 11 percent, mainly due to surprisingly poor showings against placebo.
Two comprehensive analyses of antidepressant trials have uncovered a dramatic increase in placebo response since the 1980s. One estimated that the so-called effect size (a measure of statistical significance) in placebo groups had nearly doubled over that time.