[A simpler article, written for clients, can be found here.]
For a number of years I've followed the research of Touch Research Institute at the University of Miami School of Medicine. They've been doing research on touch therapy since 1992 and have been pioneers in the field of massage therapy research in the United States. One of the markers they use in their studies is cortisol, a stress hormone that can be measured in blood, saliva, and urine.
TRI studies have repeatedly claimed that massage lowered cortisol levels. Massage therapists welcomed what appeared to be objective confirmation of the benefits of massage and embraced this information.
And then one day I read there was a study that challenged this claim.
My initial reaction was, "What? What about all those TRI studies for the last 18 years?" I wanted answers, so I tracked down Christopher Moyer, Ph.D., the author of the study. He was polite, sent me a copy of the study, and told me he'd be happy to answer any questions.
Making sense of research
If you are not accustomed to reading scientific studies, let me tell you - they are very difficult to read unless you've been trained to read them. I had no idea what the numbers meant or what the study was talking about. However, I could understand the introduction and the conclusion and what it boiled down to was this: massage didn't change cortisol levels nearly as much as had been previously claimed. The Moyer study acknowledged that massage has been shown to decrease anxiety and depression but it appeared that cortisol was not the mechanism by which this occurs.
I learned some interesting things during the course of trying to understand this study. First, I learned what is a "meta-analysis." A meta-analysis is a method of looking at all the studies that have been done on a particular subject and analyzing them as a group. Any one study may be flawed or may be a fluke. Or studies may vary widely in their results. In addition, the smaller the number of subjects, the more likely that your results may be distorted. If you have ten studies that all come up with similar results, then the results of those studies are more likely to be valid. The Moyer study looked at all the studies they could find and analyzed their results. They considered many different factors, including size of study and the quality of the study design. It was also important that the Moyer study analyzed studies from a number of different sources. If all of the studies come from only one source, there may be biases at play in that one source that do not become evident. Each person and institution comes from a particular point of view. If many sources show similar results, then that is significant. They looked at the numbers from all these various studies. What did they find? Some studies showed a decrease in cortisol, some showed an increase, some showed no change at all, but what was very consistent about the studies was that these changes were, in fact, minimal. Massage did not significantly change cortisol levels.
Coincidentally, shortly before I heard about the cortisol study I'd noticed, while doing a search on PubMed, that some studies found that massage had little or no effect on cortisol levels and one study actually showed an increase, although not very great. I thought that was curious in light of the TRI studies but didn't give it much thought at the time. Now the Moyer study was pointing this out very clearly.
In-group vs. between-group changes
There was another element of the Moyer study that I didn't understand until I watched these two videos explaining in-group and between-group comparisons. Moyer gives an excellent explanation, with graphs, that helped make sense of it all.
One way to demonstrate the efficacy of a therapy is to compare it to a control group. Perhaps one group is given a half hour massage and the control group lies down and listens to relaxing music for half an hour. In this way, you can see if massage has any more benefit than just relaxing or having caring attention for a period of time. This is where the significance of the "within-group" and the "between-group" comparisons became important. Although the cortisol levels of those getting massage dropped, so did the cortisol levels of the control groups. When the two groups were compared, they weren't all that different. Massage wasn't making nearly as much a difference as it appeared.
What does this mean for massage therapists?
At first I was disappointed because all these years I'd had an idea that seemed like a very good idea and now I'd learned it was wrong. However, I got over the disappointment pretty quickly. I'd rather have correct information than believe in, and perpetuate, incorrect information. My practice is not built on reducing cortisol, it's built on helping people feel better in whatever way I'm able and on being as honest as I can with my clients. My clients appreciate that I try to stay well-informed and be very honest with them. Since I am not running a cortisol-reduction service, I have nothing to fear! When my clients feel better, they don't care if it's cortisol or not cortisol. They just know they feel good and that's what's important to them.
So, we don't yet know exactly how massage makes us feel better, but we now know that one of the more easily measured stress hormones, cortisol, is probably not what creates that change. That's okay. I'm not going to stress about it. Massage still helps people feel really good. I look forward to the day when we know more, but for now, that's good enough for me.
Thanks to Dr. Moyer for his helpful comments during the writing of this article.
More discussion of the cortisol study can be found in the Journal Club at POEM, the Project for Open Education in Massage.