Human body is composed of different complex elements. There is a rhythm in the energy flow in the body. If it is broken and body loses its balance it gives rise to many ailments. A healer should know the reason of sickness in a body so that he can find exact treatment to cure it. In western medicine, homeostasis deals with healing practice by the balancing and maintaining body mechanisms. It is a very popular form of holistic healing and deep definitions are available on wikipedia.org
Human body contains complex internal systems and if one is disturbed the whole body mechanism is disturbed and resulting in various illnesses. It affects the energy level of the body. The energy level varies from person to person. Cancer is result of uncontrolled cell multiplication which affects the entire process of the body mechanisms, certain treatment modes like acupuncture where specially designed needles are inserted in the affected part with slow and low passage of electricity will helps to restore the health condition of a weak body. Another treatment is the usage of various herbs to be taken internally. The ability to cure the disease by a healer is entirely depending on his energy level. One method is to absorb the disease from another person aura to him and to discharge it by some method cannot be explained by science and modern techniques. A healer is always view as an experimenter as his healing capability is beyond scientific definitions.
In religious, especially Christian anthropology strongly states that mental illness is the result of sin. Only through prayer and belief it could be cured. A movie named Sybil in 1976 featuring Sally Fields picturised the life of a woman with multiple personality disorder took the complexities of mind and how its disorder affects the human body.