Intercessory prayer
In a comment to my post on Placebo logic, reader CET mentions double-blind studies on the effects of prayer. The “double-blind” means that the subjects (hospital patients) did not know whether they were being prayed for. This factors out any placebo effects, as opposed to people praying for themselves. There have been a number of such studies, with mixed results. Here are two examples:
- Byrd, 1988, showed a statistically significant effect.
- Aviles, 2001, showed no statistically significant effect.
A cautious conclusion would be that the effect of intercessory prayer, if it exists at all, is at the limits of statistical detectability. The placebo effect, on the other hand, is so strong that it is possible to measure the difference in effect between expensive placebos and inexpensive placebos.
After several thousand years of experience with prayer, one would think that the basic effectiveness would have been established long ago, and we would have moved on to more interesting questions, such as whether invoking one of the saints is more effective than praying directly to God.