Research of the placebo effect shows that yellow colored pills are more effective for depression, red pills are more stimulating, and green colored pills reduces anxiety.
In 1957, a terminal cancer patient was given a worthless drug that caused his tumors to “melt like snowballs on a hot stove.” When he found out it was proven worthless, his cancer returned. He was given a placebo version and it went away again. He learned the truth, then died soon after.
In a 2008 Duke study, patients received painful electric shocks. Afterwards, $0.10 cent placebo pills alleviated pain for 64% of study participants. $2.50 placebo pills reduced pain for 85% of participants. So it is: expensive placebos work better than cheap ones.
Placebo has an evil twin, the nocebo effect. For example, men taking a commonly prescribed prostate drug who were informed that the medication may cause sexual dysfunction were twice as likely to become impotent.