What makes you think nobody has researched it? AFAICT there's quite a lot of study on the phenomenon, and it's a lot more complex than just expectation bringin

What makes you think nobody has researched it? AFAICT there's quite a lot of study on the phenomenon, and it's a lot more complex than just expectation bringing about physiological change. Some portion of it is likely action of the immune system, general "regression to the mean" effects, and some of it is that patients who are receiving treatment are likely to report milder symtoms and less pain (so there may not always be a physiological change, just a psychological one). Either way, I don't think you can count the placebo effect as a medical miracle waiting to be exploited, or as something that medical science just ignores.