The efficacy of prayer has been studied since at least 1872, generally through experiments to determine whether prayer or intercessory prayer has a measurable effect on the health of the person for whom prayer is offered. A study in 2006 indicates that intercessory prayer in cardiac bypass patients had no discernible effects.
While some religious groups argue that the power of prayer is obvious, others question whether it is possible to measure its effect. Dr. Fred Rosner, an authority on Jewish medical ethics, has expressed doubt that prayer could ever be subject to empirical analysis. Basic philosophical questions bear upon the question of the efficacy of prayer – for example, whether statistical inference and falsifiability are sufficient to "prove" or to "disprove" anything, and whether the topic is even within the realm of science.
According to The Washington Post, "...prayer is the most common complement to mainstream medicine, far outpacing acupuncture, herbs, vitamins and other alternative remedies." In comparison to other fields that have been scientifically studied, carefully monitored studies of prayer are relatively few. The field remains tiny, with about $5 million spent worldwide on such research each year.