Studies on intercessory prayer

Some religions claim that praying for somebody who is sick can have positive effects on the health of the person being prayed for.

Meta-studies of the literature in the field have been performed showing evidence only for no effect or a potentially small effect. For instance, a 2006 meta analysis on 14 studies concluded that there is "no discernible effect" while a 2007 systemic review of intercessory prayer reported inconclusive results, noting that 7 of 17 studies had "small, but significant, effect sizes" but the review noted that the most methodologically rigorous studies failed to produce significant findings.

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. If and when more studies of prayer are done, the issue of prayer's efficacy may be further clarified.

The third party studies discussed here have all been performed using Christian prayers. Some have reported null results, some have reported correlations between prayer and health, and some have reported contradictory results in which beneficiaries of prayer had worsened health outcomes. The parameters used within the study designs have varied, for instance, daily or weekly prayers, whether to provide patient photographs, with full or partial names, measuring levels of belief in prayer, and whether patients underwent surgery.

In 1872, the Victorian scientist Francis Galton made the first statistical analysis of third-party prayer. He hypothesized, partly as satire, that if prayer were effective, members of the British Royal Family would live longer than average, given that thousands prayed for their well-being every Sunday, and he prayed over randomized plots of land to see whether the plants would grow any faster, and found no correlation in either case.

A 1988 study by Randolph C. Byrd used 393 patients at the San Francisco General Hospital coronary care unit (CCU). Measuring 29 health outcomes using three-level (good, intermediate, or bad) scoring, the prayer group suffered fewer newly diagnosed ailments on only six of them. Byrd concluded that "Based on these data there seemed to be an effect, and that effect was presumed to be beneficial", and that "intercessory prayer to the Judeo-Christian God has a beneficial therapeutic effect in patients admitted to a CCU." The reaction from the scientific community concerning this study was mixed. Several reviewers considered Byrd’s study to be well-designed and well-executed, while others remained skeptical. A criticism of Byrd's study, which also applies to most other studies, is the fact that he did not limit prayers by the friends and family of patients, hence it is unclear which prayers, if any, may have been measured.

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