I am convinced that if the mind is at peace, I will be less likely to fall ill. I am sure that a mind body connection does exist. While I cannot quote studies, I have read that it really works. Even physicians trained only in the art of healing the body, now believe in this interrelationship.
It is important to try to do exercises to clear the mind as much as is practical. Some resort to meditation. I have never been able to fully meditate by clearing my mind completely. I have however chosen escape as an alternative in clearing the mind of worry. I am a poor student of meditation, not having the patience to see it through. I guess I have not tried hard enough.
My mind is the clearest it has every been.It is so transparent its like there is nothing in it!! I worry a lot from time to time about a lot of things but there are periods I have been able to fill my mind with good things so all the worries can be temporarily set aside. This has definitely helped me in reducing the incidence of physical illness.
I live in an environment where I am constantly bitten by mosquitoes and I don't have a scar or swelling to show the next morning for all that blood sucking. I have yet to contract a mosquito borne disease, while many I know who live in less mosquito prone areas have suffered the consequences of both dengue and chickengunya.
It is a very lucky person who is fortunate to be relatively free from physical illness, but by attempting to clear the mind of worry, a definite benefit will result in both prevention, and speedy recovery from physical illness.