Prayers don't work

Several studies of prayer effectiveness have yielded null results.[9] A 2001 double-blind study of the Mayo Clinic found no significant difference in the recovery rates between people who were (unbeknownst to them) assigned to a group that prayed for them and those who were not.[116] Similarly, the MANTRA study conducted by Duke University found no differences in outcome of cardiac procedures as a result of prayer.[117] In another similar study published in the American Heart Journal in 2006,[5] Christian intercessory prayer when reading a scripted prayer was found to have no effect on the recovery of heart surgery patients; however, the study found patients who had knowledge of receiving prayer had slightly higher instances of complications than those who did not know if they were being prayed for or those who did not receive prayer.[4][5] Another 2006 study suggested that prayer actually had a significant negative effect on the recovery of cardiac bypass patients, resulting in more frequent deaths and slower recovery time for those patient who received prayers.[5]
References: Wikipedia
Benson H, Dusek JA, Sherwood JB et al. (April 2006). "Study of the Therapeutic Effects of Intercessory Prayer (STEP) in cardiac bypass patients: a multicenter randomized trial of uncertainty and certainty of receiving intercessory prayer". American Heart Journal 151 (4): 934–42. doi:10.1016/j.ahj.2005.05.028. PMID 16569567. Lay summary (PDF) – John Templeton Foundation
O'Laoire, S (1997). "An experimental study of the effects of distant, intercessory prayer on self-esteem, anxiety, and depression". Altern Ther Health Med 3 (6): 38–53. PMID 9375429.