The following recollection offered by Hazrat Inayat Khan touches on the subtle interaction between mind and the physical body, a theme which is subject to many theories and much speculation.

Once I happened to go to an asylum for the insane in New York, and the physicians very kindly laid before me a number of skulls showing different cavities in the brain and spots of decay which had caused insanity in the lives of the patients. There is always a sign of it in the patient’s physical body. It may be apparent suffering or it may be some decay at the back of it, yet not known.

I asked them, “I would like to know whether the cavity brought about the insanity, or the insanity brought about the cavity?”

Their argument was that the cavity brought about the insanity. But mental disorder is not always caused by a cavity in the brain, for the inner being has a greater influence on the physical being than the physical body has on the mental existence. Yet it is not always the mind that brings about the physical illness; very often it is so, but not always.