There is something about this in a book called "Lives of a Cell" by Lewis Thomas, M.D., published about 1972 or 73. I can't find the book, so I will just summarize what I remember of it.
He said the longevity of people in modern industrial societies was primarily due to vaccination, antibiotics, and public health measures such as good sewers and building codes. Hospitals have very little to do with it. Iatrogenic disease is much more common than laymen realize. He and his physician friends tended to be minimalists -- they didn't use each other's services for every little problem. "Most things," he said, "get better by morning."
Since reading this book, I have been a medical minimalist myself, a policy that has served me well.
He also said that there are many conditions which are easily and safely treatable, and which should be treated. A minimalist is not the same as a Christian Scientist.
It should be possible to use the placebo effect intentionally, and to learn to use it better with practice. I have made some effort to do this, but it's impossible to say whether it has had any effect on my health -- which is excellent, but which might have been excellent anyway.