A large study found that prayers from strangers had no effect on the recovery of patients who had undergone heart surgery.
In addition, patients who knew they were being prayed for experienced more post-operative complications, possibly because of anxiety due to raised expectations.
The study, which lasted almost ten years and involved more than 1800 patients, was designed to overcome flaws in previous investigations of the subject.
The study's authors stated that the findings should not be considered the last word on the effects of intercessory prayer, and that the study did not cover either personal prayers or prayers from friends and family members.
At least one earlier study seemed to indicate lower complication rates in patients who received intercessory prayers; however, others found no difference.
The current study did not find any difference between patients who were prayed for and those who were not, and a somewhat higher complication rate -- 59 percent as opposed to 51 percent -- for patients who knew they were being prayed for.