Do hopes and prayers work? Looks like that’s a no


Three double-blind studies in 20 years find little evidence that praying improves outcomes for heart patients. Andrew Masterson reports.


Praying might be a favourite response to the misfortune of others, but there's precious little evidence that it works.

Jean-Philippe Tournut/Getty Images

It happens with such regularity that, in the US at least, it has become a cliché. Every time there is a mass shooting, or a tornado hits a town, or an epidemic surges, people in positions of power offer up hopes and prayers for the victims.

This, of course, begs the question: do prayers have any effect?

It’s an important consideration, given that in modern American politics prayers are generally deployed instead of other interventions, such as, for instance, gun control laws, climate policy or affordable healthcare.

So, have the healing effects of prayer ever been put to the test by scientists? Yes, a few times, and the results are, at best, uncertain and, at worst, counter-productive.

Most tests have focussed on medical conditions and treatment, which are naturally easier to monitor and quantify than, say, the mental health of mass shooting victims and witnesses. Cardiac surgery has been a particular favourite.

In 1999, a team led by William Harris from the Sanford School of Medicine at the University of South Dakota set up a double-blind trial to test the efficacy of prayer on 990 patients admitted to a coronary care unit (CCU).

On admission, the patients were randomly assigned into two groups. The names of members of the first groups were given to groups of religious believers, who prayed for them daily for four weeks. The second group received no prayers.

The results showed that the patients in receipt of prayer had 11% fewer setbacks than those that did not. There was no difference in length of hospital stay between the two groups.

Writing in the journal JAMA Internal Medicine, Harris and his colleagues noted there was “no known way to ascribe a clinical significance” to the result, but added that further studies should be conducted.

One such was done in 2006 and reported in the American Heart Journal. This had a more complex set-up. It involved patients admitted to six US hospitals, and randomly assigned to three groups.

The first had people praying for them, but were told such a thing “may or may not” happen. The second received no prayers, but were told the same thing. The third group received prayer and was told that it was definitely happening. All up, 1800 patients were involved.

The results were curious. The two groups who did not know whether or not they were receiving prayers had almost identical levels of complications – 51% and 52%. The group which knew for sure people were putting in a good word for them with God fared significantly worse, with a 59% rate of complications.

In 2009, the Cochrane Library – an organisation that specialises in systematically reviewing other research – took a close look at the matter, poring over the methods and results of 10 studies that investigated the clinical power of prayer.

Lead author Leanne Roberts actually came from a religious background, holding a position at the Southwark Diocesan Office at Trinity House in London, UK. Despite that, she and her colleagues came away unimpressed by the data.

“These findings are equivocal and, although some of the results of individual studies suggest a positive effect of intercessory prayer, the majority do not and the evidence does not support a recommendation either in favour or against the use of intercessory prayer,” they wrote.

They added that they were not convinced enough even by a couple of apparently positive outcomes in a few of the studies to feel it was worth recommending further trials.

They concluded that they “would prefer to see any resources available for such a trial used to investigate other questions in health care”.

And that, perhaps, is an outcome we can all hope for.

This article appears in Issue 82 of Cosmos magazine. To subscribe, and have the latest science delivered direct to your door or inbox, click here.

  1. https://jamanetwork.com/journals/jamainternalmedicine/article-abstract/485161
  2. https://www.sciencedirect.com/science/article/pii/S0002870305006496
  3. https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD000368.pub3/full
  4. https://cosmosmagazine.com/issues/life-on-mars
  5. https://cosmosmagazine.com/subscribe
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