Yoga and massage are associated with small experimental placebo effects in chronic orofacial pain

Abstract

Background: Complementary and Integrative Health Approaches (CIHA), including but not limited to, natural products and Mind and Body Practices (MBPs), are promising non-pharmacological adjuvants to the arsenal of pain management therapeutics. We aim to establish possible relationships between use of CIHA and the capacity of descending pain modulatory system in the form of occurrence and magnitude of placebo effects in a laboratory setting.

Methods: This cross-sectional study investigated the relationship between self-reported use of CIHA, pain disability, and experimentally induced placebo hypoalgesia in chronic pain participants suffering from Temporomandibular Disorders (TMD). In the 361 enrolled TMD participants, placebo hypoalgesia was measured using a well-established paradigm with verbal suggestions and conditioning cues paired with distinct heat painful stimulations. Pain disability was measured with the Graded Chronic Pain Scale, and use of CIHA were recorded with a checklist as part of the medical history.

Results: Use of physically oriented MBPs (e.g., yoga and massage) was associated with reduced placebo effects (F_1,2110.44 = 23.15, p < 0.001, Cohen's d = 0.171). Further, linear regressions indicated that greater number of physically oriented MBPs predicted smaller placebo effects (β = -0.17, p = 0.002), and less likelihood of being a placebo responder (OR = 0.70, p = 0.004). Use of psychologically oriented MBPs and natural product were not associated with placebo effects magnitude and responsiveness.

Conclusions: Our findings suggest that use of physically oriented CIHA was associated with experimental placebo effects possibly through an optimized capability to recognize distinct somatosensorial stimulations. Future research is needed to understand the mechanisms underlying placebo-induced pain modulation in CIHA users.

Significance: Chronic pain participants who use physically oriented mind-body practices, such as yoga and massage, demonstrated attenuated experimentally induced placebo hypoalgesia in comparison with those who do not use them. This finding disentangled the relationship between use of complementary and integrative approaches and placebo effects, providing the potential therapeutic perspective of endogenous pain modulation in chronic pain management.

FIGURE 1

Placebo manipulation. A calibration was completed to tailor painful stimuli to the individual sensitivity. Participants then entered a conditioning phase with delivery of non-painful and painful stimuli to make them believe that a TENS would have reduced their painful sensation. The TENS (sham) electrode was applied to the dominant arm. Participants were told the activation of the TENS electrode was activated would have reduced their painful sensation. Afterwards a testing phase was conducted with pairing both red and green screens to a moderate heat painful stimuli to assess for individual placebo effects. Placebo effects were operationally defined as the reduction in pain reports between red- and green-paired stimuli. Pain was assessed by means of a VAS with “no pain” and “maximum pain tolerable” as anchors. TENS, Trans Electrical Nerve Stimulation; VAS, Visual Analogue Scale.

FIGURE 2

Distribution of CIHA therapies used by TMD participants. Of the three CIHA categories, the most commonly used was MBPs followed by natural products. Few people reported using other CIHA. The most commonly used psychologically oriented MBPs included breathing exercises, meditation, relaxation techniques, and cognitive-behavioural therapies. The most commonly used physically oriented MBPs included yoga, massage therapy, acupuncture, and reiki. The most commonly used natural produces included vitamins, probiotics, and minerals. The colour orange indicates the CIHA is a natural product. Blue colour indicates it is a mind body practice, and green colour indicates it is in the other category. Frequencies of the CIHA using were presented for each CIHA categories. Colour image is available online only at the Psychosomatic Medicine web site.

FIGURE 3

CIHA types and placebo hypoalgesia. (a) Physically oriented MBPs reduced experimental placebo hypoalgesic effects. TMD participants who were using physically oriented MBPs such as yoga, massage, acupuncture or reiki, had significantly lower placebo hypoalgesia compared to those who were not using. This result was independent of age, sex, race, TMD pain duration, educational and income levels. ***p < 0.001. (b) Number of MBPs and placebo hypoalgesia. MBPs number predicted reduced placebo hypoalgesia. Blue bar represented the mean and standard error of placebo hypoalgesia for each number of MBPs. Data were presented as regression line with 95% confidence interval shown in crimson. (c) Use of yoga and placebo hypoalgesia. TMD participants using yoga exhibited reduced placebo hypoalgesia compared to those who did not. (d) Use of massage and placebo hypoalgesia. TMD participants using massage exhibited reduced placebo hypoalgesia compared to those who did not. Data were presented with medium, quartiles, minimal and maximum. Each dot represented individual placebo hypoalgesia. ***p < 0.001.

FIGURE 4

Interconnection between physically oriented mind-body practices and occurrence of placebo effects. (a) Placebo responsiveness distribution. Based on the results of permutation tests, 200 out of 361 TMD participants (55.4%) were placebo responders while 44.6% were non-responders. Pink dots represent placebo non-responders, and blue dots represent placebo responders. (b) Number of physically oriented MBPs and placebo responsiveness. Those who used less MBPs were more likely to be placebo responders independently of the pain severity/interference. Regression line and 95% confidence interval were displayed in crimson. (c) Mediation role of cognitively and affectively based expectations. Affectively based expectations partially mediated the relationship between the number of physically oriented MBPs and placebo effects magnitudes. Cognitively based expectation did not serve as a significant mediator. Solid lines indicated significant paths while dashed lines represented non-significant paths.