placebos have been known and studied for years. I remember the scandal when a major magazine (Life?) made it public.
There are many documented studies about what is often called bio-feedback can do. The mind (whatever that is) can control many things, as various Hindu and Zen masters have shown. Exactly what 'happens' is a matter of debate, but it IS demonstrable that good and bad 'attitudes' can affect the body.
   Elderly patients have been helped with 'pet therapy'...just having a cat or dog around. We know that periods of stress can change the amounts of various chemicals produced in the body, and REDUCTION of strees can do the equivalent.
It is not easy for an individual to get these functions under direct control, but it is a growing field of research.