Not that this is of any surprise to anyone, but Ray has written often about the nervous system and the effects it has on the rest of the body. The nervous system (and by extension our body) is healthiest when metabolism is high AND when it perceives the world as purposeful, including the things we are involved in.
http://www.sciencedaily.com/releases/20 ... 124308.htm
After reading the work of A. Huxley: The Doors of Perception and Heaven and Hell. I think that many of the so-called mental disorders are problems with metabolism (eg, lack of vitamins B, C, and distribution of certain proteins, the latter describes Huxley in Heaven and Hell)