Okay let me ask you a bunch of questions, let me know what you think....
Let's setup 2 groups of people of say stage 4 Cancer or full blown AIDS, now 1 group reads the bible or whatever practices that the cristians religions require.
To the other set is with the same determination will be recited random gibberish and the necessary rituals albiet uttered with random words...Now do you think the ones who have been given the christian treatment will survive more?
Also if you have a control group that have been treated with studied drugs and no prayers, how do you think those will fare?