It's an appealing and comforting thought. Friends, family and even total strangers pray for you when you're seriously ill. When you recover, you may be grateful for those prayers. But did they contribute to your recovery? How would you know? Is it a question even worth asking?

Does prayer work?

Praying on another person's behalf to improve their health is called "intercessory prayer." And, believe it or not, researchers have attempted to scientifically study its effects on health and recovery from disease. The results are intriguing:

  • A 1988 study found that when patients in the hospital with heart disease had prayers said for them, they had less breathing trouble and required less antibiotic therapy than otherwise similar patients for whom prayers were not said.

  • A study published in 1998 suggested that prayer improved the health of AIDS patients. Although those receiving prayers had no change in an important measure of immune function over the six months of the study, they did have fewer serious illnesses, fewer doctor visits and better mood than those who were not prayed for.

  • In 1999, patients in a Missouri intensive care unit recovered faster after prayers were said for them compared with those who did not have prayers said. This study was unique due to its size—nearly 1,000 patients—and neither the patients nor their doctors knew which patients had prayers said for them.

  • A 2001 study published in the Journal of Reproductive Medicine supported intercessory prayer for women who were infertile. In that study, women for whom others prayed became pregnant twice as often as those who were not the recipients of prayer.

Skeptics criticize these studies, suggesting that the study designs were flawed or that something other than prayer could explain the findings.

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Several of the best studies of intercessory prayer in recent years have come to the conclusion that it doesn't work. For example:

  • A 2005 study from researchers at Duke University showed no benefit from distant prayers for patients undergoing high-risk heart procedures.

  • In 2006, perhaps the largest study of intercessory prayer to date showed no benefit of prayer for 1,802 heart bypass surgery patients. The complication rate was actually a bit higher for those who knew others were praying for them.

Does the answer matter?

The value of prayer is not something that scientific study can easily settle. Besides, the results are unlikely to change what people do. Here's why:

  • For advocates of prayer, the belief that it will work is enough for both the person praying and the person who is ill. And would or should a negative study stop believers from praying for others' health? This is about faith, not scientific proof.

  • Skeptics looking for scientific proof would probably not be convinced that prayer works even if studies found that prayer increased survival, speeded recovery or fended off disease. After all, such results would require a distinctly unscientific explanation—unmeasureable energy, supernatural phenomena or a religious explanation.

  • It's very difficult to maintain a good control group in studies of prayer. If assigned to the "no-prayer" group, a sick person, his family and religious strangers all over the world might still pray for him. If prayer truly is beneficial, such "uncontrolled" prayer might invalidate the study's findings.

  • It's possible that a study of prayer will find that it's harmful as the 2006 study of bypass surgery patients did. If future research confirms this finding, would doctors urge their patients, families, friends and religious groups to stop praying for the sick?

  • What if a patient died despite the prayers of family, friends and strangers? Would those who prayed blame themselves for not praying hard enough, long enough or well enough?

Prayer could be useless, but do you care?

It's natural for friends and family to hope for the best when a person is sick. To the extent that praying is an active expression of that hope, is it worth proving if it's worthwhile or not?

Doctors tend to do all they can to help patients and families maintain hope while also being realistic about the situation. Why should scientists go out of their way to scientifically analyze an activity that is nearly universal, defies logic or known scientific principle, and may discredit a source of hope?

Large, expensive studies to prove or disprove prayer seem to me a bit like trying to make a case that the chicken came before the egg. It's hard to see how the outcome of such a study could be useful, and it's unlikely to settle anything.

My guess is that when a person is ill, it may be comforting to know that others are praying for him or her. Similarly, people praying may feel that they are at least doing what they can to help.

A recent survey of more than 1,100 U.S. physicians found that 85 percent believed religion and spirituality (including prayer) had a positive influence on health and recovery. But, only 6 percent of these doctors believed it had any effect on the "hard" medical endpoints, such as speed of recovery or death. About three-fourths of these doctors thought religion and spirituality helped people cope and maintain a positive outlook. As you might expect, more religious doctors endorsed the value of religious resources, such as prayer, more readily than non-religious doctors.

The bottom line

Is the value of intercessory prayer a myth? Maybe it is. I doubt there will ever be consensus on how to answer this question. But I don't think that's such a problem.

Compared with many other unproven remedies, there is little cost or risk associated with prayer. And at the least, it provides some measure of comfort to both the people praying and the people they are praying for.

I believe that the decision to pray or not pray should be decided by individuals and those praying for them, not researchers. If I controlled the world's research funding, I'd spend it on something other than assessing the value of intercessory prayer. This will never be easily settled. And I'm not sure it should be.

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