Aug 05 2010

Proximal Intercessory Prayer

One of the core “pearls” of this blog is that not all scientific studies are created equal. It is common for the media and the public to cite the fact that “a study shows” some claim or other, but such appeals to evidence are worthless unless we can assess the quality of the study. We now have a gaggle of science bloggers – real scientists blogging about research – to help explain all the various ways to look at the quality of a study, and hopefully this is resulting in a more savvy population of science enthusiasts (the kind of people who read science blogs).

Let’s take the following hypothetical study: The study included 24 subjects who were all treated openly with the intervention in question. There was no blinding or control group – so everyone in the study, subjects and experimenters, knew that every subject was getting the treatment. The treatment involves active physical intervention with the subject. The protocol also calls for multiple interventions if initial treatments are not effective – essentially the subjects receive repeat treatments as long as possible until they report a response.

The outcome was either a change in vision or hearing. Subjects reported impaired vision or hearing at the beginning of the study and were tested with standard vision or audiology tests before and after treatment. All subjects demonstrated improvement from the intervention.

It should further be noted that the subjects in the study were not chosen from the random population but from a self-selected group that already believe in the efficacy of the treatment. Further, the authors admit, although they do not disclose the data, that previous attempts to document response to the treatment in other populations have failed.

At this point anyone with any reasonable familiarity with how to assess the quality of medical studies should see that this is a worthless study. This barely qualifies as a pilot study. It really doesn’t matter what the treatment is or how plausible it is – you simply cannot draw any meaningful conclusion from 24 self-selected subjects with no controls and no blinding.

Now, I know you can read headlines so you know this was a study of proximal intercessory prayer, but the point is – even if you assess the details of the study divorced from knowledge of what the intervention is, it should be obvious that this study tells us nothing.

The study took place in rural Mozambique among members of a Pentecostal church. The press release for the study says:

“We chose to investigate ‘proximal’ prayer because that is how a lot of prayer for healing is actually practiced by Pentecostal and Charismatic Christians around the world,” Brown said. “These constitute the fastest-growing Christian subgroups globally, with some 500 million adherents, and they are among those most likely to pray expectantly for healing.”

But there is another reason to study “proximal” prayer, which in this study meant physical laying on of hands, not just being near the subject. Studies of distant intercessory prayer have been essentially negative – we see the typical random scatter of results expected of an ineffective treatment, with no consistent pattern of positive results, and with the best studies being negative. A recent Cochrane review concluded:

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. We are not convinced that further trials of this intervention should be undertaken and would prefer to see any resources available for such a trial used to investigate other questions in health care.

Interestingly, this review was sharply criticized for being wishy washy. The “positive” studies they included in their “equivocal” assessment had major flaws that were not discussed in the review. Most notably, they included a study described in the later criticism thusly:

We have not checked all ten included trials but noted that the largest one was published in BMJ’s Christmas issue. This trial seems to be meant to amuse rather than being a scientific study, in line with the tradition of this special issue, as the trial evaluated the effect of prayer taking place 4–10 years after the patients had either left the hospital alive, or had died from their bloodstream infection. Thus, the trial evaluated the effect of retroactive intercessory prayer using historical data and its author argued that we cannot assume “that God is limited by a linear time”. The authors of the Cochrane review did not mention anywhere in their review that the patients were randomised many years after their outcomes had occurred and did not discuss the likelihood that time can go backwards and that prayer can wake the dead.

Another review of the research concluded:

There is no scientifically discernable effect for IP as assessed in controlled studies. Given that the IP literature lacks a theoretical or theological base and has failed to produce significant findings in controlled trials, we recommend that further resources not be allocated to this line of research.

Bottom line – intercessory prayer does not work. Perhaps the studies are negative because they were properly blinded – it is easy to blind a subject to the fact that someone distant is praying for them. It is much more difficult to blind someone to the fact that someone is placing their hands over their eyes and asking God to heal them and banish any demons from them, over and over again until you tell them you are better.

I find that argument that a deity is better able to heal when the person asking them to do so is physically close to the person they are praying for absurd, lame, and convenient. It is a nice excuse to unblind the protocol, and nothing else –  a way of generating false-positive results.

The authors imply that improvements in sight and hearing are objective and cannot be explained by suggestion or hypnotism, but this is naive. Any visit to a faith healer’s performance clearly demonstrates the power of suggestion in a religious context. There is even good neuroscience to document this effect – belief in the healing power of a faith healer actually inhibited the critical thinking parts of the frontal lobes of the brain. This effect is tied to the perceived charisma of the healer. This might explain why the researchers had to go to rural Africa to find positive results – maybe they are just not charismatic enough to sway Western audiences.

I will also point out that hearing and vision are subjective – even when standard tests are used, subjective feedback from the subject is necessary. This allows for subjects to exaggerate their limitations prior to treatment and try hard to perform better after an intervention.


In my opinion this study represents a larger trend that I have discussed before – clinical research going backwards in quality after higher quality studies yield negative results. We have seen this with acupuncture – after well-controlled trials were negative, some proponents decided that “pragmatic” (i.e. unblinded) studies were better. We see this with homeopathy, where well-controlled studies are negative and then dismissed because treatments were not individualized.

Now we are seeing the same pattern with intercessory prayer. The research is clearly negative, so now some proponents are turning to “proximal” intercessory prayer, which just happens to require unblinding.

In the final analysis it is all an elaborate excuse to dismiss high quality negative studies in favor of low quality studies that are more likely to yield false positive results.

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