Scientific Studies of the Effectiveness of Intercessory Prayer

By Darwins Beagle - Posted on April 20th, 2007
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There is a long history of scientific investigation on prayer with mixed and contradictory results. However, I think now there is enough information to come to a rather strong tentative conclusion. It doesn’t work.

The first study I am aware of on the effectiveness of prayer was made by Sir Francis Galton. Galton was an interesting person. He was a cousin of Charles Darwin. He pioneered the science of biometry (the application of statistics, systems analysis and engineering to the life sciences). He also was a strong advocate of eugenics.

In his prayer study Galton reasoned that many people pray for the health of the King. If prayers were answered then kings should live longer than well-to-do but not regal people. He took a look at records and found they live less long. So he concluded that the effectiveness of prayer was not supported.

More recently there have been a number of studies published in peer-reviewed scientific journals. Four in particular have made a “media splash”. The first three were hailed as scientifically showing the power of prayer without critical analysis. The last study was one which used over 2 million dollars in grant money, involved several centers, had the best controlled model. It failed to show a positive effect for prayer.

I will critically evaluate all four studies and show you that in actuality the other three didn’t either.

Study 1: Positive therapeutic effects of intercessory prayer in a coronary care unit population. Byrd, R.C. (1988). Southern Medical Journal, 81:826-829.

This was the first on the scene. It was hailed as the first double-blind study on the effects of intercessory prayer. Byrd looked at 393 patients who were admitted to the coronary care unit of San Francisco General Hospital. The patients were divided into 2 groups. The experimental group contained 192 patients; the control group contained 201 patients. Both groups were told that people may pray for them as part of a scientific study. However, only the experimental group actually received prayers.

The intercessors (the people who did the praying) were “born again” Christians. Their normal religious activity included daily prayer and regular church attendance. They were affiliated with several protestant sects and with Roman Catholicism. Each patient in the experimental group was assigned to between 3 to 7 intercessors. The intercessors were told the first name, diagnosis, and general condition of the patient. They were also told of pertinent updates to their condition. Intercessory prayer was done daily until the patient was discharged from the hospital. Each intercessor was told to pray for a “rapid recovery and prevention of complications and death”.

Experimental and control groups were compared on 29 different outcome measures during their hospital stay. The experimental group fared statistically significantly better on 6 of those criteria. They were congestive heart failure (4% of the experimental group and 10% of the control group developed congestive heart failure); Diuretics (5% of the experimental group and 8% of the control group required drugs that stimulate the kidneys to reduce fluid volume); Cardiopulmonary arrest (2% of the experimental group and 7% of the control group had a period in which their heart stopped and required electrical stimulation to restart); Pneumonia (2% of the experimental group and 7% of the control group came down with pneumonia); Antibiotics (2% of the experimental group and 9% of the control group required antibiotics during their hospital stay); and Intubation (0% of the experimental group and 6% of the control group required intubation during their hospital stay).

That sounds pretty good, doesn’t it? In every case in which a significant difference was found the group that received prayer fared better than the control group. Prayer works … or so it seems. But just reporting the results is not critically examining the study. To do that one needs to look at the design of the study and the results that were not statistically significant.

The first thing to note is that there was no statistical differences in what most of us would consider the most important outcomes. Patients in both groups had similar mortalities. There was no difference in the length of their stay in the CCU or in the hospital. No statistical difference in the cases of unstable angina, readmissions to the CCU, coronary angiography, or major surgery. The prayers for the patients specifically asked for speedy recovery (no difference between controls and experimental groups), no deaths (no difference between controls and experimentals), and no complications (no difference in MOST indices). So the question that immediately arises is why some things and not others. No obvious answer arises, nor does any testable hypotheses immediately jump to mind. That is never a good sign.

Dr. Byrd claimed that his was a double blind study. Neither the patients nor the persons determining the outcome were aware of who was being prayed for. In fact Dr. Byrd claimed that the patients, the staff doctors, AND HE, HIMSELF were all “blinded”. So in a sense that is triple blinded. That is the way such studies should be done. In studies like this it is important. Why?

The reason is that presumably it would be Dr. Byrd who is entering the data. Data entry is a boring and monotonous job. Mistakes can easily be made. Also mistakes can be unconsciously be made especially in times like that. As Richard Feynmann said the most important thing in science is to not fool yourself, and the first step in doing that is to realize that you are the most easy person to fool.

Unfortunately, it was discovered afterwards that Dr. Byrd did not enter the data. The data was entered by his assistant Janet Greene. She was also the one who assigned patients to each group. She also gave the names of the patients to the intercessors. She closely monitored each and every update. She was totally unblinded. … That is not the way to do it. Each and every place is a place where her personal biases can enter into the experiment.

So the judgment from this study alone is that there are some intriguing signs that prayer may work. But there also some intriguing unanswered questions and some disturbing methodological flaws.

Study 2: A randomized, controlled trial of the effects of remote, intercessory prayer on outcomes in patients admitted to the coronary care unit. Harris, W.S., et al. (1999). Archives of Internal Medicine, 159:2273-2278.

This study was hailed as a “truly blind” study that replicated and supported Byrd’s 1988 study. But did it really? Here is what the study reported.

990 patients from the Mid America Heart Institute (MAHI) were divided into experimental and control groups. There were 524 patients in the control group and 466 in the experimental group. Neither patients nor doctors were told of the study so both were unaware that an outside group was praying for anyone.

The intercessors had a variety of Christian backgrounds. 35% were non-denominational; 27 % were Episcopalians; the rest were from different protestant and Roman Catholic sects. 87% were women. The mean age was 56 years old. All said they agreed with the statement, “I believe in God. I believe that He is personal and is concerned with individual lives. I further believe that He is responsive to prayer for healing made on behalf of the sick.” All prayed daily and attended church at least weekly. A group of intercessors was given the name of a patient only. They were instructed to pray for “a speedy recovery with no complications” and anything else they deemed appropriate. They were told to pray for 28 days regardless of the outcome of the patient. They were not given any updates on the patient’s condition.

Experimental and control groups were compared over 35 different outcome parameters. These parameters were then evaluated on a scale invented by the MAHI that rates outcomes on a graded scale. Each time the patient needed some type of medical intervention he was given points. The lower points were given for simpler procedures. The higher points were given for more serious complications. The highest (6 points) was given for death. A patient’s total score is the arithmetic total of all the scores throughout his hospital stay.

It was found that the score for the experimental group was better than the score for the control group by 11%. This was statistically significant at the P=.04 level. That means that only 4% of the time should you expect to get results like that if there really isn’t any difference between the groups you compare.

Harris et al. proudly proclaimed that they had successfully replicated Byrd’s study and the news media so reported it that way. However, they had not. In order to see that we need to look at the study critically.

Byrd had found statistically significant difference between experimental and control groups on 6 of his 29 outcome measurements. They were Congestive Heart Failure, Cardiac Arrest, Pneumonia, Diuretics, Antibiotics, and Intubation. Each of these is included in the Harris study. But there is no statistically significant difference between experimental and control groups on these parameters in the Harris study. In fact, Harris found no statistically significant difference on ANY of his 35 outcome parameters.

The statistical difference that Harris gets is only when the results are lumped together and “cooked” in a rather subjective grading scale. It appears as though the authors were searching to find something significant. In reality, even the Byrd study can be criticized for this. One needs to specify exactly what factors one wants to look at before these types of studies are performed. If one uses enough parameters one should find things that appear statistically significant but are only so due to chance. Thus, my interpretation of the scientific evidence regarding the effectiveness of prayer at the point of the Harris study is one that says the two studies contradict each other and no viable claim can be established.

Study 3: Does prayer influence the success of in Vitro fertilization-embryo transfer? Cha, K.Y., Wirth, D.P., Lobo, R.A. (2001). Journal of Reproductive Medicine, 46:781-787.

This study was widely touted as evidence of prayer affecting fertility. It was even hailed as a potential breakthrough by Dr. Timothy Johnson on ABC’s Good Morning America. It has become a BIG LESSON of caution for researchers purporting beneficial effects of the supernatural … although you would never know it if you limited yourself to the popular media coverage.

In this study the authors looked at the fertility rates of women being implanted with embryos at a fertility clinic. Looking at this single trait avoids the problem in the two studies above in which a shotgun approach is taken to search for statistical significance. Both the women being implanted and the doctors doing the implanting were unaware that prayer was going on. Excellent double-blind technique.

The fertility rate in the experimental prayed-for group was 50% while in the control not-prayed-for group it was 26%. Almost a 100% increase… a robust phenomenon. All of these things are things we like to see in a study.

Furthermore, two of the authors were faculty members at Columbia University School of Medicine. One, listed as the study’s primary author, Dr. Rogerio A. Lobo, was chairman of Obstetrics and Gynecology at Columbia. You couldn’t ask for better qualifications than that. So then what was the problem with the study?

The answer is the third author. Daniel Wirth it turns out is a big time con man. Soon after the study was published Mr. Wirth was indicted on fraud charges. E had bilked Adelphia Communications out of 2.1 million dollars by infiltrating the company’s computers and having the company pay for unauthorized consulting fees. An investigation into his background showed that he had used an alias, John Wayne Truelove, to obtain a passport and make several trips abroad. He bilked the Social Security Administration out of $103,178 by having his father’s social security checks sent to him for 10 years after he had died.

While none of these things deal with the article directly it does cause one to wonder. What was Mr. Wirth’s role in the study anyway? It turns out he did almost everything. Although Dr. Lobo was listed as the primary author, Dr. Lobo later admitted he knew nothing about the study until a year after it was over. His TRUE role was to give advice on the wording of the article, check out the statistics, and to facilitate publication … Dr. Lobo was on the editorial board of the Journal of Reproductive Medicine.

Dr. Cha ran the fertility clinic. He was responsible for collecting the data on the people being prayed for. He used the protocol developed by … Daniel Wirth. Mr. Wirth collected the data from the intercessors. He is also the one who collated the data. There was plenty of opportunity for fraud.

Since the paper was published Dr. Cha has left Columbia. He works at his own fertility clinic. Dr. Lobo has requested that his name be dropped from the article. He claims that it was erroneously put on there in the first place (despite the fact that he was initially referred to as the primary author). He has stepped down as chair of the Department of Obstetrics and Gynecology. He is no longer on the editorial boards of any journal. Both Cha and Lobo are effectively out of science and deservedly so.

Mr. Wirth is serving a 5 year prison sentence after having pleaded guilty to all counts of fraud against him.

So, as it turns out this paper is almost certainly fraudulent and offers no support for the efficacy of prayer. At this point I would say that the scientific data is becoming decidedly against it in fact. If the phenomenon were real one would be expecting to see something by this time.

Study 4: Study of the therapeutic effects of intercessory prayer (STEP) in cardiac bypass patents: A multicenter randomized trial of uncertainty and certainty of receiving intercessory prayer. Benson, H., et al. (2006). American Heart Journal, 151:934-942.

This was a highly publicized research project from the moment of its inception. It was funded primarily by the John Templeton Foundation. It was supposed to be the definitive study on the efficacy of prayer. The Rolls Royce of prayer studies, if you will. It is a huge study. It involves several prestigious heart centers. The researchers were familiar with appropriate design of blinded studies. In short, it was a study that prayer aficionados were looking forward to for almost a decade.

A total of 1802 patients completed the study. The patients were all scheduled for non-emergency coronary artery bypass surgery. They were randomized to 3 different groups. Group 1 consisted of 604 patients that received intercessory prayer after being told that they may or may not receive it. Group 2 consisted of 597 patients that did not receive intercessory prayer but as in group 1 they were told that they may or may not receive it. Group 3 consisted of 601 patients that were told they were definitely going to receive intercessory prayer and did receive it.

So Group 1 received intercessory prayer but were unsure whether or not they were going to receive it. Group 2 didn’t receive intercessory prayer and were unsure whether or not they were going to receive it. Group 3 received intercessory prayer after being assured they were going to receive it.

The intercessors were from two Catholic groups and one protestant group. A list of patients to be prayed for was posted at a central location within each church and the intercessors were to pray “for a successful surgery with a quick, healthy recovery and no complications.”

The data was collected by independent auditors reviewing patient records. All investigators, participating nurses, interviewers, and auditors were blinded as to which group the patients were assigned.

The results were devastating for the efficacy of prayer. The complication rates were as follows:

Group 1 patients - 52.5% (received prayer; uncertain if they would)

Group 2 patients – 50.9% (did not receive prayer; uncertain if they would)

Group 3 patients – 58.6% (received prayer; certain that they would receive it)

The first thing to notice is that the complication rate was significantly higher than either the Byrd or Harris et al. studies. The authors attribute this to the thoroughness of the independent auditors. If this is so then it raises further questions about the first two studies.

Group 3 patients experienced a significantly higher complication rate than did Groups 1 and 2. Why this should be isn’t clear. The authors speculated that perhaps knowing they were being prayed for may have unconsciously convinced them they were sicker than they really were.

The other interesting finding is that Group 1 patients had higher complications than did Group 2 patients. This did not quite rise to the level of statistical significance. However, when the researchers looked at the patients that they had classified as having a major complication then the results did reach statistical significance. Group 1 patients had major complications 18% of the time while Group 2 patients only 13%.

Thus, the group of patients that received prayer did statistically worse than those who didn’t even though neither group was certain as to whether or not they were to receive it. This is another result that is hard to explain.

The authors noted that during the design of the experiment they had elected to include in the major complication group patients that they had lost contact with. It was assumed that the most likely reason they would lose contact with the patient was because the patient would have suffered some major complication and be unavailable for follow-up. There were 35 such patients in the major complication groups. When these patients were eliminated from analysis the results were no longer statistically significant. So the authors suggest that the overall result even though statistically significant were really due to chance.

The results have certainly been criticized. Most of the criticism comes from theological sources and center on the inappropriateness of trying to quantify God. I find this criticism rather disingenuous. I am sure that had the results come out showing that prayer was efficacious these same sources would have found nothing inappropriate trying to “quantify God”.

One valid scientific criticism of the study is that prayer by outside sources was uncontrolled for. It would be impossible to do so. I cannot imagine family members and friends so inclined to pray foregoing such activity to aid in the scientific investigation on the efficacy of prayer. However, this type of prayer is true for control and experimental groups. In a study as large as the STEP study, it should even out.

Other criticisms have come from fringe groups. Some say that the type of prayer is important. The basis for this seems to be the Spindrift studies. These studies were carried out by Christian Scientist members Bruce Klingbeil and his son John Klingbeil between 1969 and 1993. They took plant seeds, stressed them in salt water, planted them in pans, prayed for one side and not the other. They reported that the prayed-for side produced more plants than did the non-prayed-for side. They further prayed in two different ways. One in which they asked God to make the plants grow more robustly – directed prayer. And another way in which they asked God to do what was in the best interest of the plant – undirected prayer. They reported that while both prayers made the plants do better than non-prayer, undirected prayer worked the best. All of the prayer studies listed above used directed prayer (actually the Cha et al. study on fertility claimed to use both directed and undirected prayer, but it is unlikely the study actually did either). So, claim these prayer enthusiasts, it is no wonder the results are equivocal.

But the Spindrift studies were never published in a peer-reviewed scientific journal so were never subjected to formal scientific scrutiny. Furthermore, the studies are bathed in a sea of suspicion. The Klingbeils did publish their results on their own. But very shortly after they published their results both of them committed suicide. Why? Some people claim it was because they were persecuted by both the religious and scientific communities. They were supposedly about to be excommunicated from their Christian Science church (I do not know why). The science establishment had poo-pooed their research.

I certainly do not know why they committed suicide, but they seem to have been a strange family. Here is a quote from an review of a book detailing their life. The quote comes from Deborah Klingbeil, Bruce’s daughter and John’s sister:

As the daughter of Bruce Klingbeil and the brother of John (the two researchers whose work is documented in this book) I read Journey Into Prayer with special interest. I can attest personally to the truth of the incidents in the book. I found the book especially helpful as a resource for newcomers to prayer research who are carrying on my dad's research work because it gives them a sense of context and history. I disagree somewhat [w]ith the author's opinion of the suicides given in this book. I talked on the phone to my dad and brother just hours before their death and I was the only person in communication with them at that time. Based on what they told me, which they asked me not to make public, I felt the suicides were a concession made in order to keep the research from dying entirely while the author of this book states that he feels the suicides sabotaged the research. I gave the suicides my blessing before and after they occurred not because I believe in suicide (which I do not) but because I do believe in concessions that advance the greater good. The author expresses that he thinks the suicides were caused by negative energy. …

What?? The suicides were a concession made in order to keep the research from dying entirely?? She gave the suicides her blessing before and after they occurred?? That seems to be one strange family! It makes no sense to me.

To my knowledge in the 14 years since their suicide no one has replicated their results. From this there is no reason to put any credence in the idea of directed vs undirected prayer.

Other people claim that what is important is the relationship of the person doing the praying to the person being prayed for. These are just the type of studies that the lead author, Herbert Benson, was familiar with. Dr. Benson is head of the Mind/Body Medical Institute at Harvard University. He had written several books extolling the power of prayer. His work had been criticized extensively, however. For one thing he never used a control group. In one study he reported that spiritual relaxation by using prayer increased the likelihood of a woman achieving pregnancy by 35%. It turns out that what he really did was see women who had unexplained infertility problems. He told them to relax and pray. After doing so 35% actually became pregnant. How many would have become pregnant if they would have gone home and read Harry Potter or something innocuous like that? No one knows because it was not controlled for.

If a person has a lot of family members praying for him and he gets better is it because of the praying or is it because of the family support? No one knows, it hasn’t been checked. Thus, there is no reason to assume this is a valid criticism either.

The problem with these fringe objections is that they are ad hoc. One can always come up with potential ad hoc reasons that studies don’t work out the way one wants. The simplest (and most likely correct) answer to failed experiments is that the phenomenon one is examining isn’t like one thinks it is. In this case the way the phenomenon of intercessory prayer is most likely to be different than one thinks it is, is in its very existence. But that is often hard to accept.

It should be noted that many (if not all) of the authors of the STEP study were devout theists. Besides the lead author’s advocacy of prayer, several other authors were hospital chaplains. It comes as no surprise that the implications of their study were hard for even them to accept.

For instance, in the discussion section of the paper the report says, “Private or family prayer is widely believed to influence recovery from illness, and the results of this study do not challenge this belief.” Er … it seems to me that it does at least challenge that belief. The study rather clearly implies that intercessory prayer is ineffective. If intercessory prayer is ineffective with strangers then why would it not cast at least a shadow of doubt on “private or family prayer”? Why is private or family prayer such a different entity that the study would have no bearing on it?

Dean Marek, a hospital chaplain at the Mayo Clinic and coauthor of the study said after the study was published, “you hear tons of stories about the power of prayer, and I don’t doubt them.” Really?? Why not? Why was it not shown in the study?

Bob Barth, spiritual director of Silent Unity, the protestant organization that provided intercessors, said, “A person of faith would say this study is interesting, but we’ve been praying for a long time and we’ve seen prayer work, we know it works, and the research on prayer and spirituality is just getting started.” How does he “know” it works? If it is so obvious that it works, why didn’t the study show it?

The real reason this doesn’t challenge their belief in the power of prayer is that they believe in prayer despite the evidence. It is called “faith” and in this case seems to be directly opposed to reason. Tell me again … why is this a virtue?

But in any case, this study … large in scope and lacking the methodological problems plaguing the Byrd and Harris et al. studies … certainly give no support to the efficacy of intercessory prayer.

So what is the story on prayer so far? These are by no means the only studies published on prayer. They are just the ones that have received the most attention. There are many others and the results are like these … mixed and contradictory. None are as well controlled as the STEP studies however.

As of this point, the efficacy of prayer has been diligently looked for and our best data says it doesn’t exist. This is telling. If the phenomenon was real, studies should have demonstrated it by now. They don’t. Barring extremely impressive results to the contrary in the future, my opinion is that intercessory prayer has been shown to be ineffective beyond a reasonable doubt.


Darwin's Beagle