(h/t Bodhi Haraldsson for bringing this to my attention)
Interestingly, at the same time that the Journal Club is examining the effects of massage on cortisol, Arthritis Today just came out with an article on the benefits of massage therapy for people with arthritis, where the research on that claim is mentioned. You'll also see a couple of familiar names from Journal Club quoted in that article.
In the section titled "How Does Massage Work?" they repeat the claim that massage can lower cortisol levels:
While some studies show that massage can reduce pain and anxiety for people with arthritis, how exactly does massage make these results happen? Research has shown that massage can lower the body’s production of the stress hormone cortisol, and boost production of serotonin, which, in turn, can improve mood. Additionally, massage can lower production of the neurotransmitter substance P, often linked to pain, and improve sleep as a result.
They follow up with another study where the reduction in cortisol levels was not significant:
In 2010, researchers at the University of California, Los Angeles, School of Medicine and the nearby Cedars-Sinai Medical Center studied 53 healthy adults receiving just one Swedish massage therapy session and found that the participants’ levels of key hormones and white blood cells were positively affected. For example, the hormone arginine-vasopressin, which may lower blood pressure, was decreased, along with some inflammatory cytokines like IL-4 and IL-10. Cortisol levels were reduced by massage in this study as well, although not significantly.
and then they proceed to the research we're discussing in Journal Club.
Commenters Christopher Moyer (first author on the Journal Club research article) and rchunco (who is facilitating this month's Journal Club are quoted in the article. It's definitely worth a read.
I also find the claim about substance P interesting, and worth a follow-up. The Arthritis Today article doesn't mention the provenance (source) of the claim, stating only that:
massage can lower production of the neurotransmitter substance P, often linked to pain, and improve sleep as a result
To follow up, I did a PubMed search on
massage AND "substance P"
and got 5 results, the following 2 of which bear relevance to the claim:
Abstract: Many animal species invest a large amount of time in grooming behavior without deriving any apparent benefit. In order for this behavior to have survived, however, it must confer some survival advantage. In seven of eight humans tested, an elevation in the skin's temperature was documented after massaging of the cheeks of the face. The elevation of the skin's temperature reached a plateau after about 40 min of massaging and was correlated to visible erythema. This effect could be inhibited by repeated pretreatment of the skin with topical capsaicin, a chemical that results in the release of substance P from peripheral nerve endings. Thus, it appears that the temperature elevation induced by stroking of human skin is controlled, at least in part, by release of the neurotransmitter, substance P. In conclusion, it appears that the release of neurotransmitter(s) may be the survival advantage that grooming confers to animals.
Abstract: Massage therapy has been observed to be helpful in some patients with fibromyalgia. This study was designed to examine the effects of massage therapy versus relaxation therapy on sleep, substance P, and pain in fibromyalgia patients. Twenty-four adult fibromyalgia patients were assigned randomly to a massage therapy or relaxation therapy group. They received 30-minute treatments twice weekly for 5 weeks. Both groups showed a decrease in anxiety and depressed mood immediately after the first and last therapy sessions. However, across the course of the study, only the massage therapy group reported an increase in the number of sleep hours and a decrease in their sleep movements. In addition, substance P levels decreased, and the patients' physicians assigned lower disease and pain ratings and rated fewer tender points in the massage therapy group.
Reading the abstracts instead of the articles is never safe; there are just too many errors in published articles and too much lack of detail to rely on the abstract to fairly represent the article enough to base an analysis on.
But I can read an abstract and decide on that basis whether it makes sense for me to go to the effort and expense of obtaining the entire article or not.
The first one may be interesting, based on the abstract. I think they make quite a huge leap from the results of their study to the conclusion that grooming necessarily confers a survival advantage in animals, and that that survival advantage may lie in the release of neurotransmitters. However, the abstract itself is necessarily quite telegraphic, for reasons of space, and the article itself may do a better job of connecting those dots.
But the evolutionary biology claims aren't what we're interested in here. We're looking for the source of the claim that massage lowers levels of substance P, and there is enough information in the abstract of the article to determine the answer to that question.
Morhenn is claiming the following:
40 minutes of firm massaging of the cheeks leads to
increased temperature [C] in the facial skin.
Topical capsaicin pretreatment inhibited massage from producing these results [D].
Therefore, the temperature elevation caused by massage involves--at least as part of the process if not the entire cause--release of the neurotransmitter substance P.
If, at this point, you're wondering whether you missed a step, no, it's not you. Morhenn is using one piece of knowledge implicitly--she is assuming that all her readers already have all the pieces--rather than stating it explicitly.
That piece of knowledge is that since capsaicin causes peripheral nerve endings to release the neurotransmitter substance P, and there is a lag time before they "recharge" with more substance P to release, that when the massage is taking place, there is temporarily no more substance P left for anything else to cause to release.
So her implicit (not fully spelled out) argument is that since massage causes increased temperature, etc. and that since this effect no longer occurs when capsaicin has caused the peripheral nerve endings to discharge their substance P, that the reason massage effects are blocked must be that massage produces its effects (at least, in part) through that very release of substance P. Since it's no longer there, due to the capsaicin, massage cannot produce the effects it normally would.
I can't tell from the abstract whether she's connected the dots thoroughly enough for a convincing interpretation--I'll have to look up the article later--but what I can tell is that this is not the source of the claim that massage reduces substance P.
In fact, Morhenn is claiming the opposite--that massage causes substance P to be released in this situation--so while I'll have a look later to see whether she connected the dots, both on this claim and on the larger evolutionary biology argument--I'll put it aside as a source for the claim in the Arthritis Today article.
That leaves only the Field article as the source of the claim, and indeed it is stated in the abstract. Since--as we're examining in Journal Club--her team used a weaker, non-standard methodology for the claims that massage lowered cortisol, I suspect the same may be true in their analysis of substance P levels.
I won't have a chance to get out to the medical library until this weekend, but when I do, I'll check it out, and report back on my findings.