Stop me if you've heard this one.
In 1939, before there were drugs for angina pectoris, Italian surgeon David Fieschi developed a surgical technique for improving the outcomes of angina patients. The technique was called mammary ligation. It involved tying off the internal thoracic artery, which is a paired artery (one on each side of the sternum) supplying blood to the anterior chest wall and breasts, as a way of forcing additional blood to go to the heart. By the 1950s, Fieschi's operation was a mainline surgical intervention for angina, with success rates of 80% to 85%.
But in the late 1950s, two teams of surgeons (in Kansas City and Seattle) decided to do a sneaky bit of testing. They divided their angina surgery patients into a placebo group and a treatment group. The treatment group got the full mammary ligation. The placebo subjects were cut open under general anasthesia, their internal thoracic arteries exposed; and then they were sewn shut.
The published results were as remarkable as they were controversial. The treatment group's success rate was 73%, whereas the success rate among patients who got the sham surgery was 83%. See Cobb et al., New England Journal of Medicine, 1959 May 28;260(22):1115-8 and Dimond et al., American Journal of Cardiology, April 1960;5(4):483-486.
Patients in the sham group were quite convinced they were cured. One said: "I can do anything except real hard lifting. I am running farm equipment and maybe using one nitro a week. I used to need fifteen a day. Believe me, I'm cured."
The Cobb and Dimond mammary ligation studies show better than any drug study just how powerful the placebo effect can be. Angina is potentially debilitating. Yet the placebo effect brought pain down to manageable levels in people who had sham surgery, 80+ percent of the time. Is it any wonder acupuncture works for so many people? Or hypnosis? Or Prozac, Paxil, Celexa, Zoloft, Effexor, and all the rest?
For more on sham surgeries, see this 2006 paper. and this paper from 2011.