The Placebo effect, when it is from a pill, is increasing at a rate of about seven percent each decade. In other words, if 30 percent of a group of depressed people responded to placebos in 1970, 50 percent of that group would respond to them today. Such use of placebos suggests that as a culture we are putting more and more hope in our pills. The placebo effect is a measure of our confidence—the trust we place in a particular object. Those who put their trust in witch doctors might die from his voodoo threats because they believe in witch doctors. Those who trust in pills might report some healing from placebos because they believe in medication. As long as psychiatric medications are perceived as the deepest treatment for depression, the placebo effect will flourish.
Ed Welch in a research Review in The Journal of Biblical Counseling, Fall 2002, pg. 77.