If you are interested, here is a web page where someone has summarized many of the scientific studies of intercessory prayer. I have not read any of these studies in order to tease apart the methods. Luckily for me, Dr. Candy Gunther Brown from Indiana University has done such work and is familiar with the methods. She writes:
Researchers have attempted to design double-blinded, controlled trials of distant intercessory prayer. Intercessors are typically given the first name and condition of someone they do not know and told to pray for a complication-free recovery. Researchers base conclusions on the efficacy of prayer solely on whether subjects in the experimental group exhibit better health than those in the control group.
At this point, I have a very serious theological problem with such studies. From a Christian perspective, I would not expect God an answer such prayers. Give some people the first name and condition of someone they do not know and tell them to pray for a complication-free recovery and, presto, God is forced to act? I previously mocked Stenger’s approach to science here. Is there anyone who can make the case that such prayer studies are substantively different from my parody?
Look, in order to get a scientifically valid conclusion, the research must assume that God is like some magical force that can be compelled to act with the right incantation. From a scientific perspective, a study which replaced prayer and instead focused on saying a magic formula would be exactly the same. Yet from a theological perspective, we Christians do not think God is a magical force and we do not think of prayer as a magical formula that gives us the power to manipulate this force. This is why it is irrational for atheists to ignore theology when they claim science can pass judgment on theology.
So it would seem that if we decided to favor the studies that show negative results, all that science has done is to determine that God does not behave like a Magic Genie. But that is what Christianity has always taught. Does this then mean that negative prayer study results are scientific evidence for the truth of Christianity?