The Study Question
Previous meta-analyses and systematic reviews of massage have concluded that there is weak to moderate evidence that massage may reduce stress, depression, anxiety and cortisol, and enhance some immune parameters. However, the conclusion is always that more rigorous studies are needed. In spite of the popularity of massage with consumers and increasing acceptance by the larger health care system, relatively few studies have investigated the mechanisms by which massage produces its effects on the interrelated immune and neuroendocrine systems.
This study investigated the effects of Swedish massage over five weeks on neuroendocrine and immune outcomes as compared to a light-touch intervention. The hypotheses tested were that (1) there would be cumulative effects of five weeks of massage compared to the light-touch intervention on outcomes measured; (2) the effects would last beyond the end of the intervention session; and (3) twice-weekly interventions would enhance the cumulative effects of weekly massage or light touch.
The Study Methods
Eligibility criteria for participants included normal physical examinations, without psychiatric diagnoses. Exclusion criteria included nicotine use, illicit drug use, active medical problems or regular medication use, pregnancy, shift work, dieting, more than two drinks per day or a history of binge drinking within the last six months. Outcome measures were mean differences between massage and light touch on oxytocin, arginine vasopressin (AVP), adrenal corticotropin hormone (ACTH), cortisol, lymphocyte markers (CD4+, CD8+, CD25+ and CD56+ cells) and cytokine levels (interleukin (IL)-5, IL-10 and IL-13).
Fifty-three participants entered the study and were randomly assigned to one of four intervention groups, receiving Swedish massage once a week or twice a week for five weeks, or a light-touch control condition once a week or twice a week, again for five weeks. Forty-five participants (22 male and 23 female) completed the study. Eight participants dropped out for reasons unrelated to the study intervention, including scheduling conflicts (3), use of prescription medications to treat injury or illness (4) and personal disagreement with the therapist (1). Participants who dropped out did not differ from study completers on any baseline measures.
The 45-minute massage therapy interventions were performed between 3 p.m. and 7 p.m. by licensed massage therapists using a standardized, specified protocol with unscented oil. The light-touch condition followed the same protocol, but with the therapist using only light touch performed with the back of the hand. Fidelity to each protocol was monitored with quality control procedures, including supervision.
Data were analyzed using analysis of variance (ANOVA), and compared baseline and post-treatment values for each outcome variable at week five and at week four to assess both the cumulative effect of treatments and any sustained effect prior to the last treatment of the series.
A Cohen's d treatment effect size was also computed for massage versus touch separately for twice-a-week and once-a-week dose groups, as well as a dose effect (twice-a-week versus once a-week) separately within massage and touch groups. Effect size is a more clinically meaningful test than statistical significance.
There were no baseline differences in demographic or outcome variables among the four groups. Compared to the light-touch control condition, weekly Swedish massage stimulated a sustained pattern of increased circulating lymphocyte markers and decreased cytokine production. These results are similar to a previously reported study of a single massage session by the same research team. However, effects on hypothalamic–pituitary–adrenal function were minimal.
In contrast, within the group receiving twice-weekly massage, increased oxytocin, decreased AVP and decreased cortisol levels were observed. There was little effect on circulating lymphocyte markers and a slight increase in interferon-γ, tumor necrosis factor-α, interleukin (IL)-1b and IL-2 levels, suggesting increased production of pro-inflammatory cytokines.
No large effect-size differences for neuroendocrine measures between once-weekly and twice-weekly massage sessions were detected using either analytic approach. Twice-weekly touch, however, had a consistently greater moderating effect on all stress-related hormones than once weekly touch, especially for ACTH.
Limitations of the Study
Limitations include the small sample size of the four comparison groups relative to the number of outcome variables. Because the participants were young, healthy volunteers, this study may underestimate the effects for stressed or ill individuals. Because it is a pilot study, more research with a larger sample size is needed to confirm these findings.
Implications for Evidence-Informed Practice
This pilot study suggests that there are sustained cumulative effects of repeated massage and light touch on neuroendocrine and immune functions in healthy volunteers, and that these differ by dosage. Weekly massage increased circulating lymphocyte markers and decreased cytokine production with a minimal effect on HPA function. Twice-weekly massage appears to potentiate neuroendocrine differences. One implication is that weekly massage may be better for conditions where increasing circulating lymphocytes would be beneficial, while twice-weekly massage may be better for moderating the effects of stress-related hormones.