claimed that patients who are being prayed for recover more quickly or more frequently although critics have claimed that the methodology of such studies are flawed, and the perceived effect disappears when controls are tightened. One such study, with a double-blind design and about 500 subjects per group, was published in 1988; it suggested that intercessory prayer by born again Christians had a statistically significant positive effect on a coronary care unit population. Critics contend that there were severe methodological problems with this study. Another such study was reported by Harris et al. Critics also claim that the 1988 study was not fully double-blinded, and that in the Harris study, patients actually had a longer hospital stay in the prayer group, if one discounts the patients in both groups who left before prayers began, although the Harris study did demonstrate the prayed for patients on average received lower course scores (indicating better recovery). One of the largest randomized, blind clinical trials was a remote retroactive intercessory prayer study conducted in Israel by Leibovici. This study used 3393 patient records from 1990 to 1996, and blindly assigned some of these to an intercessory prayer group. The prayer group had shorter hospital stays and duration of fever. Several studies of prayer effectiveness have yielded null results. 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. Similarly, the MANTRA study conducted by Duke University found no differences in outcome of cardiac procedures as a result of prayer. In another similar study published in the American Heart Journal in 2006, 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. 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. Many believe that prayer can aid in recovery, not due to divine influence but due to psychological and physical benefits. It has also been suggested that