Does Prayer Cure Cancer? What Studies Show

That prayer, particularly prayer offered on someone's behalf, can cure cancer or measurably improve the odds of surviving it. The claim shows up in two very different places: in sincere religious hope, and in marketing by people selling healing services. This page is about what has been measured. It is not about whether prayer is worth doing.

Researchers have tested this. When people are randomly assigned to be prayed for by strangers without knowing it, their medical outcomes have not been better than the outcomes of people who were not prayed for. No trial has ever shown that prayer changes cancer survival, tumor response, or recurrence, because no trial has measured those things.

The largest study is the Study of the Therapeutic Effects of Intercessory Prayer, published in the American Heart Journal in 2006. It enrolled 1,802 patients having coronary artery bypass surgery at six US hospitals, and prayer was offered for fourteen days starting the night before surgery. Among patients who were told they might or might not receive prayer, complications within 30 days occurred in 52% of those prayed for and 51% of those not prayed for. The authors' conclusion was that "intercessory prayer itself had no effect on complication-free recovery."

The MANTRA II trial, published in The Lancet in 2005, randomized 748 patients undergoing cardiac procedures and reported that "neither masked prayer nor MIT therapy significantly improved clinical outcome."

A Cochrane systematic review pooled ten trials with 7,646 patients. Its authors wrote that the findings "are equivocal" and that "the evidence does not support a recommendation either in favour or against the use of intercessory prayer." A separate meta-analysis of fourteen studies found an overall effect that "did not differ from zero."

In the 2006 trial there was a third group, told with certainty that they were being prayed for. Complications occurred in 59% of that group, compared with 52% of the group told they might or might not be. Both groups received exactly the same prayer. The difference was in what patients were told about it.

This is sometimes reported as "prayer made people worse." That is not what the study showed, and the authors did not say it. Being told that strangers are praying for your survival before heart surgery is a piece of information, and information changes how people feel. Whatever produced the difference, it was not the prayer, because the prayer was identical in both groups.

Almost nothing about disease outcomes. The one substantial cancer trial, run at a hospital in Adelaide and published in 2012, randomized nearly a thousand patients and measured spiritual wellbeing on a questionnaire. It found a statistically significant but very small improvement, on a measure of how people felt rather than how their cancer behaved. Two thirds of participants completed follow-up. It did not look at survival, scans, or recurrence.

The National Cancer Institute's professional summary on spirituality in cancer care discusses coping, spiritual distress, and quality of life at length. It contains no claim that prayer affects cancer survival.

An early study from 1988, of 393 coronary care patients, reported that a prayed-for group did better. It is still cited constantly. Later reviewers pointed out that it examined a large number of outcomes without specifying in advance which one mattered, which makes a positive result much easier to find by chance. A 1999 replication attempt found a difference on a newly created composite score but no difference in length of stay in intensive care or in hospital. A widely publicized 2001 study reporting that prayer doubled IVF success was later removed from the journal's website and one of its authors was removed from the paper.

There is also a simpler reason. Most people who share these claims are not selling anything. They are frightened, or they love someone who is sick, and the claim offers something to do.

The danger is not prayer. It is substitution and blame. Delaying a biopsy, stopping a treatment, or declining pain relief because healing is expected can cost a person options they cannot get back. And when the cancer progresses anyway, a framework in which prayer works if you do it properly leaves the patient carrying the failure. The Catechism of the Catholic Church addresses this directly, in a line worth knowing whatever your tradition: "even the most intense prayers do not always obtain the healing of all illnesses."

Trials of prayer as a medical intervention have not found an effect, and none of them studied cancer outcomes. That is a real finding and it should be stated plainly. It is also a narrow finding. It says nothing about whether prayer is meaningful, whether faith helps a person carry an illness, or what a person owes their own beliefs. Those questions were never on the study forms.