How prayer and faith affect health
Twerski, AJ. 2006.  BH 16:95-104. CELD ID 21480

Abstract
Repeated studies leave little doubt that prayer has a salutary effect on recovery from illness. What is not as clear is the mechanism whereby this effect occurs. Religionists have no problem in attributing the effect of prayer to Divine benevolence, G-d's responding to prayer. They struggle however, with the problem of how a person's prayer can cause G-d to act differently than He would have without the prayer. It is a tenet of faith that G-d does not undergo any change. those how do not ascribe to Divine intervention say that the serenity and reassurance brought about by prayer are responsible for its effects. That emotions can affect disease and recovery is no longer debatable, and the mechanism whereby this occurs has essentially been elucidated. The effect of others praying for the patient can be similarly effects of prayers for a patient even when the patient is unaware that he is being prayed for are more difficult to explain.