This week’s edition of Nature Neuroscience carried a paper with the title “Adenosine A1 receptors mediate local anti-nociceptive effects of acupuncture“. The paper was not without interest, but it tells one nothing about acupuncture in humans.
The mice had their paws injected with rather unpleasant stuff called Complete Freund’s Adjuvant. This makes them inflamed and sore, so they are unusually sensitive to pain. When the mice were pierced with human-sized needles, and the needles rotated, they responded a bit less to painful stimuli.
The newspaper reports of this paper were even worse than usual.
The worst of the lot was Richard Alleyne, in the Daily Telegraph: “Acupuncture does work as it stimulates a natural pain killer, scientists find“.
Fiona McCrae in the Daily Mail was marginally better, with “Let’s get straight to the point, acupuncture DOES ease pain“. At least she manages to include a brief critical comment from Edzard Ernst.
Even the usually-excellent Ian Sample in the Guardian was unusually gullible with “Acupuncture may ease pain by triggering release of natural painkiller“. The subheading did say the study was done in mice not man, but there was no critical comment and, as in the other reports, no attempt to summarise what’s known already about acupuncture.
When this sort of misreporting occurs, it often seems to come from the press release (another case documented here). Many journalists never get any further than the press release, Here is Nature‘s press release.
How needles pierce pain
Acupuncture can relieve many kinds of pain, but it remains unclear how it might work, beyond the possibility of a strong placebo effect. A study published online in Nature Neuroscience now shows that acupuncture locally activates pain-suppressing receptors which could be the key to the treatment’s ability to relieve pain.
Maiken Nedergaard and colleagues inserted fine needles into the mouse equivalent of a traditional acupuncture point near the knee, and rotated these needles intermittently as is practiced by acupuncturists. This alleviated the pain reactions of mice with an inflamed paw, and it also strongly increased the local tissue concentration of the neurotransmitter adenosine. Pain relief required the presence of a particular adenosine receptor. It is known that this receptor resides on pain-transmitting nerve fibers and can reduce the activity of these fibers. The authors found that no pain relief or adenosine elevation was observed when the needles were simply inserted into the acupuncture point without rotation. They also noted that a drug that prolongs the lifetime of adenosine in live tissue helped to prolong the pain-attenuating effect of mouse acupuncture.
It should be noted that while this work suggests a mechanism for local pain relief by acupuncture, it does not in any way endorse the ancient mystical idea that the needles work by correcting some aberrant “qi” energy flow along “meridians”. Instead, the authors propose a model whereby the minor tissue injury caused by rotated needles triggers adenosine release, which, if close enough to pain-transmitting nerves, can lead to the suppression of local pain.
The title, and the first sentence, are tendentious, to put it mildly. The false assertion that "Acupuncture can relieve many kinds of pain" misrepresents entirely the current state of the evidence. A lot has been written about acupuncture, not least on this blog, but the current position can be summed up roughly as follows.
- It has been found time and time again that no difference can be detected between real and sham acupuncture in blind comparisons, and
- a non-blind comparison between acupuncture and no-acupuncture usually shows some advantage for the acupuncture, but the effect is small, transient and very variable. A recent review from the Nordic Cochrane group concluded the effect was barely big enough to be clinically significant.
The odds are that acupuncture is no more than a theatrical placebo.
The press release should have made all this clear, but failed to do so. But then the paper itself also failed to make the context clear.
The abstract of the paper starts "Acupuncture is an invasive procedure commonly used to relieve pain." The second paragraph starts "Although the analgesic effect of acupuncture is well documented, little is understood about its biological basis". It is simply not true that "analgesic effect of acupuncture is well documented". It is not. Try reading Barker Bausell’s excellent book, “Snake Oil Science” if you want to know about the strength of the evidence.
The whole paper is written with the underlying premise that acupuncture works, and all that needs to be done is to explain why. How the paper got past the referees in its present form beggars belief.
Journals like Nature Neuroscience, like it or not, have a certain prestige. Of course, the prestige is exaggerated, and like all journals, it has some good papers and some poor ones. With that prestige comes responsibility to ensure that press releases are accurate. But one often has the impression that press releases are written with the aim of getting wide press coverage, and prestige for the journal, rather that as critical evaluations of the science. This is one such case.
Martin Rees said today, in his first Reith lecture, that "science is organised scepticism". It should be, and in the long run, it is. This paper is an exception and sadly it isn’t alone.
Other commentaries on this paper
There have already been some excellent commentaries on blogs. As so often, the best bloggers are sharper than the scientific journals. If it were not for the fact that my comments on Twitter got some criticism from Nature, I wouldn’t have bothered to add to the following excellent analyses.
Ed Yong, in the Discover site was quick off the mark with A biological basis for acupuncture, or more evidence for a placebo effect?. This provides more detail than I’ve given here. It also has an intriguing postscript.
“PS: The paper notes that the authors have no competing financial interests that might have affected their work. However, it is worth noting that one of the co-authors, Jurgen Schnermann, is married to one Josephine Briggs. Briggs is the director of the National Center for Complementary and Alternative Medicine [NCCAM], an institute that has had its fair share of controversy in the past.”
NCCAM is, of course the branch of the US National Institutes of Health that has spent over a billion dollars of US taxpayers’ money without coming up with a single good treatment. This is rather fascinating, because the report in the Telegraph ends with a laudatory comment from, ahem. Dr Josephine Briggs.
Dr Josephine Briggs, director of the National Centre for Complementary and Alternative Medicine at the National Institutes of Health in the US, said: “It is clear that acupuncture may activate a number of different mechanisms.
“This carefully performed study identifies adenosine as a new player in the process. It is an interesting contribution to our growing understanding of the complex intervention which is acupuncture.”
James Cole at the Stuff and Nonsense blog has another take on the same work, under the ironic title Acupuncture Works, Say Scientists
At Respectful Insolence, Orac gives a superb and thorough account. Read it: When what an acupuncture study shows is much more interesting than what acupuncture believers think it shows.
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