I did a google search and found this, among other things:
One of the most cited studies in prayer literature was conducted by the physician Randolph Byrd in 1988. Byrd looked at the effects of prayer in the Judeo-Christian tradition in a coronary care unit (CCU) population. Over ten months, 393 patients admitted to the CCU were randomly assigned to a treatment group that would receive distant prayers, or a control group that would receive no prayers.
Three to seven people prayed daily for the rapid recovery, and prevention of complications or death, for a single patient in the treatment group. The end result was that statistically significantly fewer patients in the prayer group required ventilation, antibiotics, had cardiopulmonary arrests, developed pneumonia, or required diuretics.
I did a google search and found this, among other things:
http://scientificinquiry.suite101.com/article.cfm/pray-for-me