Mechanisms of Mindfulness-Based Pain Relief
Mindfulness-based pain relief shows promise as a supplement, or alternative to drug treatments. Given the prevalence of chronic pain, and the use of opioids for pain relief, this approach may help to reduce treatment costs and the risks of drug dependence. In their review, Zeidan & Vago (2016) found the mechanisms of mindfulness-based pain relief to be distinct from placebo, and associated with the experience level of meditators. Less than a week of mindfulness training can reduce subjective pain intensity and unpleasantness. However, long-term meditation reduces the unpleasantness of pain, without reducing its subjective intensity.
Past experience, expectations, mood and desires are among many cognitive and affective processes which can both increase and decrease the subjective experience of pain. The distinction between the sensory and higher cognitive and affective aspects of pain mirrors a central Buddhist distinction between often unavoidable sensory pain, and additional discomfort which arises dependent on the response to pain sensations. Mindfulness interventions (MIs) have been shown to reduce a wide range of chronic pain conditions including fibromyalgia, migraine, chronic pelvic pain and irritable bowel syndrome. These reductions are produced by a different mechanism to the neurochemical effects of other non-pharmacological interventions, the most well understood being the endogenous opioid system.
Despite MIs being susceptible to placebo effects, randomised controlled trials (RCTs) comparing MIs with placebo indicate that different neural mechanisms underlie their analgesic effects. Compared with a 3-day health enhancement relaxation program, an intensive 3-day mindfulness program reduced the inflammatory stress hormone interleukin-6. Mindfulness based stress reduction (MBSR) lowered inflammatory response after a social stressor, and resulted in lower experimentally-induced pain ratings compared with a Health Enhancement Program control. Four sessions of 20 minute mindfulness were significantly more effective than placebo cream, and sham meditation at reducing pain intensity and unpleasantness. Brain activation in this study suggested that pain relief in the mindfulness condition was a top-down process, in contrast to a more bottom-up process in the sham meditation condition. Finally, a double-blind study found that neither naloxone (an opioid inhibitor) or a saline placebo reversed the analgesic effects of mindfulness meditation.
Notwithstanding the methodological challenges of finding suitably matched control groups, neuroimaging studies show differences in long-term meditators’ subjective evaluation of pain. Compared with age-matched controls, long-term Zen meditators (who weren’t meditating at the time) showed significant deactivation in pain evaluation brain regions, and this was associated with lower pain reports. Expert Tibetan meditators showed reduced activity in regions associated with pain anticipation compared with a control group who practiced 30 minutes of mindfulness meditation daily for one week. In response to noxious electrical stimulation, expert vipassana meditators (whilst meditating) showed no difference in pain intensity ratings, but lower unpleasantness ratings compared to matched controls. These analgesic effects were associated with changes in brain activation consistent with other literature.
As few people will invest the time necessary to reach these levels of expertise, other research has considered the analgesic effects of short-term MIs. After four 20 minute mindfulness meditation training sessions, meditating participants rated a concurrent noxious heat stimulus as 40% less intense, and 57% less unpleasant than when not meditating. Neuroimaging indicated that high level processes, including cognitive and affective control of pain, and the contextual evaluation of sensation interacted with regions associated with attenuating incoming pain signals. In contrast with long-term meditators, less experienced meditators appear to downregulate pain intensity in addition to unpleasantness.
Taken together, these findings appear to show that differing degrees of mindfulness-meditation experience reduce the subjective experience of pain by the ways in which they decouple the cognitive and affective from the sensory components of painful experience.
Zeidan, F., & Vago, D. R. (2016). Mindfulness meditation-based pain relief: a mechanistic account: Mechanisms supporting mindfulness-based analgesia. Annals of the New York Academy of Sciences, 1373(1), 114–127.
Link to Original: https://doi.org/10.1111/nyas.13153