Mythbusting: Massage Reduces Cortisol
This is a modified version of a blog post I wrote for the Association of Massage Therapists in 2019 as part of a series that challenged some common but unfounded notions of the massage industry.
You can find the original blog @ https://blog.amt.org.au/index.php/2019/12/10/mythbusting-massage-reduces-cortisol/
What is Cortisol?
Cortisol is a stress hormone produced by the adrenal gland that essentially helps fuel the “fight or flight” response that we so often hear about. However, unlike adrenaline, which spikes in high stress environments, cortisol has a slow burning effect and is responsible for the management of inflammation, blood pressure, blood sugar and energy levels amongst other important bodily functions.
How Does It Work?
What Can Go Wrong?
Normally once a threat or stressful situation passes, cortisol levels go back down to normal and all is well. However, some people are constantly in high stress or threatening environments, forcing them to constantly redistribute/reprioritise resources to help deal with the stress. As time continues, other vital areas that haven’t been afforded the resources required begin to show symptoms and a declined level of health as a result (anxiety, depression, heart disease, weight gain, memory function etc.).
So, What About the Claim That Massage Reduces Cortisol?
“Massage reduces cortisol” is a very specific claim and given that cortisol levels can be measured (saliva/blood/urine), finding some evidence that cortisol levels decreased post-treatment should do the trick and we can all carry on claiming “what we always knew”.
But wait! it’s also really important that we compare these treatment levels to a control group so we can see if it was the massage that made the difference in the levels measured and it wasn’t just a natural regression.
What Can Be Found in The Research to Help Us Examine This Claim?
This paper was one of the first narrative reviews on the effects of massage therapy and is largely based around the many works of the author (she was involved in 39 of the 66 referenced works).
The original assertion that massage is beneficial at reducing cortisol comes from this influential paper. However, the findings this claim is based upon are all from the same laboratory (The Touch Research Institute or TRI) and, given the narrative format, a number of crucial details surrounding the studies and findings are not explored in this paper.
The team of Christopher Moyer and co decided to up the game in 2004 and produce a meta-analysis of the massage therapy research. They sacrificed their sanity and went as far as collating the results to produce a standardised mean difference effect size so that the effects of MT could be compared against control treatments. Hell, they even accounted for significant results that may have been influenced by publication bias.
Talk about taking one for the team to help clean up the mixed bag of studies so that we can see quantifiable, objective and replicable results. This is what they found.
“Only seven studies that assessed the effect of MT on cortisol with data sufficient for meta-analysis were located; six of these seven studies were from TRI. Meta-analytic results indicate that MT recipients, on average, had cortisol levels that were only 0.14 standard deviations lower than recipients who had experienced a wait-list condition or a comparison treatment (e.g., engaging in progressive muscle relaxation), a small and nonsignificant (95% CI = −0.10, 0.38) effect. The authors concluded that cortisol levels were not significantly reduced by MT, and noted that this conclusion differs markedly from that reached by Field (1998)).”
Field et al Return Serve
This time they doubled down on the claim and implied that massage therapy can decrease cortisol levels on average by 31%. They came to this figure by identifying 17 studies from research performed at their own institute (Touch Research Institute), which examined the effect of massage on cortisol and calculated the average percentile decrease in cortisol levels.
On the surface this sounds fantastic and I can understand why therapists continue to preach this as gospel.
BUT there are some warning lights flashing on the credibility dashboard when you look at how they got to this number.
Warning 1: They only used studies they conducted. (When a mining company insists on using their environmental impact study and excluding an independent report – would you accept it on face value?)
Warning 2: Regardless of the number of participants in a study, each was weighted the same. They also could have used a more rigorous approach to calculate effect sizes rather than manipulating averages which doesn’t give you an accurate story.
If you pick your groups right and manipulate how you report the data, you can make anything sound great … or gross.
For example, here is some research on the number of massage therapists who love massaging hairy backs:
Therapists who love massaging hairy backs
90%+75%+10% = 175% > > > 175%/3= 58.3%
Over 50% of massage therapists love massaging hairy backs!!
214ppl/32ppl = 6.68%
6% of therapists have a secret fetish for hairy backs!!
Warning 3: Control group data was omitted, so it is impossible to tell if the effect is better than the control and the changes, if present, are attributable to the intervention provided.
Claim – My moon dance has a 100% success rate at making the sun go down.
Evidence – I dance every night and the sun has never failed to go down.
^Sounds Legit ^
Control group – No dancing. Sun still went down.
^Moon dance boy has slick moves but he doesn’t make the sun go down^
The Studies, Reviews and Updates Continue
This review focused only on two studies that measured salivary cortisol in paediatric samples who had received massage. Post-massage test results displayed a small and non-significant effect, which reflects the results in adults highlighted in Moyer et al (2004).
Despite no change in methodology to address the limitations of the 1998 paper, the authors published this updated paper and came to the conclusion that “we can confidently say that stimulating pressure receptors under the skin leads to a cascade of events including … decreasing cortisol, which may facilitate immune function”.
Without taking into consideration studies which have conflicting findings to their own, it is hard to use this finding as a supporting argument to the claim that massage therapy reduces cortisol.
Moraska et al took a look at the physiological adjustments to stress measures following massage therapy. They performed a review of the literature in 2008 that included a larger number of studies as there was no exclusion of studies that had insufficient data for the calculation of effect size.
Whilst the review of the literature takes a look at the findings of the included studies, it does not conduct a detailed review of how the studies were designed and conducted, which leaves it susceptible to findings which may not be as credible when the methodology is broken down and accounted for. When reading statements such as the one below taken from the review discussion and conclusions section, we need to keep in mind the quality of information being reviewed.
“Our review of the literature indicated that massage therapy may have a beneficial effect on several physiological variables, specifically salivary cortisol and heart rate, when assessed immediately pre-post massage, but is null or inconclusive for the multiple-treatment effect on physiological indices of stress. A reduction in salivary cortisol was evident following a single massage treatment, yet salivary cortisol returns to initial values when assessed at a later time point, even if massage therapy was administered during the interim timeframe. The single-treatment effect, however, recurred as successive massage sessions also showed to be generally effective at lowering salivary cortisol.”
Not to leave any stone unturned, Moyer et al revisited the question and performed a comprehensive quantitative review of the topic.
In a non-conventional approach, they opted to review the literature using a percentage of change methodology as done by previous groups, as well as a conventional meta-analytic approach which is more rigorous and addresses the many confounds (other variables that are not being directly manipulated by the researchers) which are overlooked when using the percentage of change approach.
Overall, massage therapy’s ability to reduce cortisol resulted in mostly small and non-significant changes. However, they did find statistically significant changes in cortisol reduction when looking at the multiple-dose effect on children, although there were only 3 studies to draw from.
Interestingly, when they looked at the within-group percentage, they generally found smaller reductions than previous reviewers using this approach. But these results were still inconsistent with the findings of the more rigorous approach to assessing treatment effects.
Should/Can We Continue to Claim That Massage Reduces Cortisol?
Based on the current body of evidence, there isn’t much to support this claim.
Small changes may be seen but given how clinically insignificant they are, it is a stretch to suggest massage therapy has any real, direct effect on cortisol levels.
The argument for cortisol reduction often gets linked to the proven effect massage has on state and trait anxiety and depression but this is not the case and perpetuating such a claim without the supporting evidence often tarnishes our professional credibility.
As a profession that is continually looking for better recognition and acceptance of the wider medical community, it is important that we appraise the available research to the same standards that they will look to hold us to. Although it can be challenging to accept that many claims made previously about massage simply do not have the support of the evidence base, good research helps to guide further research. Every therapist can attest to the positive changes our clients have sought and received through massage therapy, and they will continue to vote with their feet. The current trend to overstate, glorify and outright make crap up in an effort to garner attention and generate business at the expense of professional credibility makes us no better than modern day snake oil salesman. Those who came before us made huge advances on our behalf with very limited resources (imagine manually searching for research and having to travel to meet and talk with fellow therapists) but a strong desire to better understand what they were doing for the people who sought their help. We need to ask the tough questions, embrace the unknown and, most of all, be open to change as a profession so that the potential for further integration of our services in the health space continues to grow.
Let’s be better.