3 Meditation and Pain Perception

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Meditation is a Buddhist derived cognitive control practice in which an individual sustains attention nonjudgmentally on the current moment. It redirects attention away from thoughts of past or anticipatory experiences when they arise[1].

Meditation is being used for pain control[2]. Many studies have shown that meditators experience a painful stimulus differently than non-meditators [e.g. 3-6]. Pain has a strong subjective component. It is for this reason that clinicians are studying the application of medication to pain management.

Currently, research lacks a clear and universal understanding of the therapeutic mechanisms behind meditation as a modulator of pain [7]. Meditation research could provide a better understanding of the subjective nature of pain perception and potentially provide the opportunity of improving non-pharmacological analgesic treatments.

Pain

The Need for Pain Management

Persistent pain is pervasive. A stratified survey of over 2000 Canadians found that 29 percent of respondents are currently experiencing pain that has lasted at least six months[8]. Similarly, according to the Institute of Medicine, as many as a third of Americans experience chronic pain[9]. The Centers for Disease Control report that a quarter of Americans have had a day-long occurrence of pain within the past month[10]. Although pain is a necessary experience to alarm the body of assaults or damage, persistent pain impacts both the individual and society at large. In the United States, lost productive time and health care expenses contributable to pain costs as much as 635 billion dollars annually[3]. This cost is more than for cancer or heart disease[3]. Although many drugs are currently prescribed to treat pain, several of them have severe side effects, such as addiction and vomiting, and some have limited empirical support for their long-term benefit11.

Psychology of Pain

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Henry Beecher
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Until World War II, pain studies assumed that a pain stimulus produced a proportional painful feeling; the greater the pain stimulus, the greater the resulting pain. Henry Beecher, a Harvard Medical school graduate who served as a military doctor during the war, challenged this assumption. While in the military, Beecher observed that numerous soldiers with severe injuries showed little to no signs of pain while in the combat zone[12]. Consequently, he conducted an observational study of 225 newly, severely wounded soldiers. It was found that three quarters of the soldiers felt not enough pain to accept the offer of pain relief medication. This observational study concluded that during battle, wound severity often does not correlate with the degree of discomfort resulting from that wound[13]. Beecher postulated that if a wound does not necessarily lead to pain then perhaps the perception of pain could be treated without the use of drugs[12]. It raised the question that if we modulate these psychological factors, can we attenuate or even eliminate the experience of pain like in the case of many World War II wounded soldiers?

The Power of Meditation
Dr. Herbert Benson demonstrates Tibetian monks changing their body biochemistry through meditation.

When looking at ways to control the psychological aspects of pain, many approaches were examined and studied. One of these proposed solutions is meditation. Meditation had already been shown to decrease psychological stress[2]. It is used as a method of relaxation. Meditation could also induce physical changes in a meditator, lowering oxygen intake and increasing skin resistance, signs of lower stress levels[14]. For these reasons, meditation was an eminent candidate to attempt to control the psychological factors of pain. The video below demonstrates the ability of meditation to control physiological changes.

Meditation Practices

Meditation is a mental practice that promotes a state of non-judgmental observation through self-regulating attention[15]. Although it is an umbrella term for a variety of practices that achieves this mental and physical state, in general, meditation techniques can be divided into two distinct classes of mental practices[15]. Many different terminologies exist in the literature for these divisions of meditation but the most used terms in recent scientific publications are focused attention and open monitoring.

Focused Attention

The premise of focus attention techniques is to engage attention on a single entity for a set period of time. The specific fixation of attention varies with the style of meditation. In transcendental meditation, attention is focused on a mental sound. Focusing on breathing or a single visual object are other common points of fixation. Focused attention is often a prerequisite for the second class of meditation practices called open monitoring[15].

Open Monitoring

Open monitoring is regarded as a moment-to-moment nonjudgmental state of awareness. During open monitoring, there is an awareness of the entire environment surrounding the practitioner. They are conscious of their environment but they do not attach themselves to thoughts. Learning to segregate each moment in time from the next is an important concept associated with this class of meditation. This segregation is to help avoid judgment and interpretation of the environment. Zen practitioners of ZaZen use this approach[15]. Unlike focused attention, open monitoring emphasizes awareness, which is more of a passive activity than attention. Although, focused attention and open monitoring emphasize different techniques to achieve mental control, both divisions of meditation practices ultimately lead to disengagement from thought.

Mindfulness

The mental state achieved through meditation is often termed mindfulness.
Consequently, many research papers use the word mindfulness interchangeably with meditation. In these papers, mindfulness encompasses both focused attention and open monitoring[16]. However, the use of the term mindfulness in research at large is ambiguous. Mindfulness meditation can also refer to the practice of open monitoring only. This is an important consideration that must be addressed when interpreting research papers on meditation.

Meditation Influences Pain

Since psychological factors have an impact on pain, it can be deduced that there are at least two components to pain. One component is the actual pain message relayed from the pain stimulus. The second component of pain is the overall experience of pain, the unpleasantness of the pain. The overall experience of pain consists of two components:

Pain intensity: the level of awareness of the pain signal from the pain sensors
Pain unpleasantness: the discomfort associated with a painful stimulation

Experimental studies

A series of experimental studies have examined the use of meditation to reduce the feeling of pain. Often in these papers, a painful stimulus is applied to expert meditators and controls during a meditative state and at rest. Self reported pain ratings are recorded. For example, using this experimental approach, Perlman et al. found that experienced long term Tibetan meditators, when practicing open monitoring, could decrease their experience of pain[6]. In this study, highly trained Tibetan meditators as well as age/gender matched novice meditators received painful heat while practicing open monitoring. The Tibetan practitioners and the novice meditators did not differ significantly in their pain intensity ratings but the Tibetan practitioners reported significantly less pain unpleasantness during the heat stimulations6. Another study by Gard et al. confirmed these results[3]. These studies show that meditation experience can lessen pain. They suggest that the meditators remain fully aware of the pain sensations but have less discomfort of the pain.

Zen meditation also appears to lessen pain[5]. Highly trained Zen meditators and age/gender match controls with no meditation experience were asked to mindfully attend to heat induced pain. Pain intensity ratings were reduced by 18 percent in the Zen meditators and pain unpleasantness ratings were reduced by 23 percent when in a mindful state compared to a non-meditative state. Controls reported no significant differences in pain experience ratings[5]. These behavioural studies are examples of the research at large, which suggest that meditation can decrease the experience of experimentally-induced pain.

There are some inconsistencies in the studies on meditation. While all studies on meditation show a reduction in pain unpleasantness, some papers demonstrate a reduction of pain intensity and others do not.

There is an explanation to account for the differing results on the impact of meditation on pain intensity. Meditation that uses the practice of focused attention reduces both pain intensity and unpleasantness. Since focused attention is directed to a single entity, such as a sound, the mind is no longer focusing on the pain stimulus. This could account for a reduction in pain intensity. Behaviorally, this appears similar to distraction which is known anecdotally and experimentally to lessen pain intensity. In contrast, when applying a pain stimulus to experimental subjects using meditation, the open monitoring meditators report less unpleasantness but not reduced pain intensity. Open monitoring meditators are aware and experience their surroundings including any pain stimuli. This could explain why the pain intensity is not reduced during open monitoring[7].

It is important to note that studies using experienced meditators can correlate meditation to pain reduction but they do not show that meditation causes pain reduction. It is possible that someone who takes up meditation and takes the time to routinely practice it is significantly different from the remaining population and this can account for the results[16].

The seminal paper by Zeidan et al. shows causality of meditation on pain management[7]. Its methodology is significantly different from the earlier studies. It employed an experienced meditation instructor to train 15 healthy volunteers in a focused attention meditation practice for four days, 20 minutes daily. These volunteers received thermal noxious stimulation and self reported the intensity and unpleasantness of the pain after stimulation, both prior to and following focused attention training. Remarkably, after meditation training, on average, these volunteers reported a 57 percent decrease in pain unpleasantness and a 40 percent reduction in pain intensity. Importantly, since the meditators had a very short training period, this shows that meditation has clinical applicability.

Clinical studies

In the clinical setting, meditation is operationalized in structured health care programs known as mindfulness based interventions (MBIs). MBIs are a group of similar programs used clinically to treat a variety of physical conditions, including pain[2]. The most common form of MBIs used for pain suffers is Mindfulness-Based Stress Reduction (MBSR). MBSR is an 8-week, two hour daily program, that focuses on training patients with open monitoring meditation. It emphasizes the incorporation of a non-evaluative observation state in everyday life. This program also includes sessions of hatha yoga to which the individual mindfully attends to the body during this exercise[2]. Click here to read more about MBSR.

Clinicians need to know whether MBRI is an effective treatment for reducing stress and persistent forms of pain. A meta-analysis was published in 2011 that investigated the efficacy of MBSR as well as other mindfulness based intervention techniques that are used for pain intervention[17]. This meta-analysis surveyed 22 studies and determined that these techniques were not very effective at reducing pain. It is important to note that uncontrolled studies were included in this survey of the literature. In contrast, a review of controlled studies on chronic pain patients and MBIs published in the same year concluded that these techniques may reduce pain but small sample sizes limit the certainly of their findings[18].

A definitive conclusion on the effectiveness of mindfulness-based interventions (MBIs) to treat chronic pain cannot be made based on the current scientific literature. In contrast, it is consistently reported that meditation decreases experimentally induced pain. This inconsistency may be a result of the large number of poorly designed clinical studies and/or the type of meditation used in a clinical setting. To improve the clinical successes, it may be a matter of determining why successful studies achieve the intended results - the reduction of pain.

Neural Studies

Two key studies examined open monitoring meditators while experiencing pain using brain imaging techniques. Using fMRI, Grant et al studied Zen practitioners using open monitoring techniques but not during meditation[19]. This study found increased activity in the sensory areas of the brain and decreased activity in the emotional and evaluating areas of the brain. Refer to the diagram for the specific brain areas. The decreased activation is proportional to the amount of experience of the meditator. A similar activation and de-activation pattern in the brain was reported in a study conducted by Gard et al[3]. Interestingly, no other psychological factor shown experimentally to decrease pain, has shown to simultaneously lessened the experience of pain while increasing activity in sensory-related brain regions[20].

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The difference in brain activity between painful and non-painful stimulation in A) meditators and B) controls. Orange is strong activity for painful stimulation. Blue is low activity for painful stimulation.

For meditators: increased activity was found in anterior thalamus, insula (INS), anterior cingulate cortex (ACC), and the secondary somatosensory cortex (SII); decreased activity was found in the medial prefrontal cortex (mPFC), orbitofrontal cortex (OFC), amygdala, hippocampus, caudate, and the dorsolateral PFC (DLPFC).

For meditators: increased activity was found in anterior thalamus, insula (INS), anterior cingulate cortex (ACC), and the secondary somatosensory cortex (SII); decreased activity was found in the medial prefrontal cortex (mPFC), orbitofrontal cortex (OFC), amygdala, hippocampus, caudate, and the dorsolateral PFC (DLPFC).

Increased activation in sensory-related brain regions is consistent with the methodology of open monitoring as this practice involves awareness of the entire environment that surrounds the practitioner. Decreased activation in the emotional/executive areas of the brain indicates a suppression of the unpleasantness feeling[19].

The Grant et al and Gard et al studies suggest that there are benefits to long-term meditation practice. Importantly, these papers suggest that the meditative state can be induced when not meditating[4]. Experienced meditators demonstrated pain reduction and similar neural patterning whether in an open monitoring state or not4. Further support for the impact of meditation on the non-meditative state was obtained from the Grant et al structural MRI studies[4]. They found that physical neural changes due to extensive meditation include an increase in density of the grey matter in sensory areas of the brain (midcingulate cortex and bilateral SII). This demonstrates that meditation effects structural changes to the brain.

Bibliography
1. Brown, C. A, and Jones, A. K.P. Mediation experience predicts less negative appraisal of pain: Electrophysiological evidence for the involvement of anticipatory neural responses. Pain 150, 428-438 (2010)
2. Carlson, L. E. Mindfulness-Based Interventions for Physical Conditions: A Narrative Review Evaluating Levels of Evidence. ISRN Psychiatry (2012).
3. Gard, T. et al. Pain attenuation through mindfulness is associated with decreased cognitive control and increased sensory processing in the brain. Cereb Cortex 22, 2692-2702 (2012).
4. Grant, J. A., Courtemanche, J., Duerden, E.G., Duncan, G. H. & Rainville, R. Cortical thickness and pain sensitivity in zen meditators. Emotion 10, 43-53 (2010).
5. Grant, J.A. & Rainville, P. Pain Sensitivity and Analgesic Effects of Mindful States in Zen Meditators: A Cross-Sectional Study. Psychosomatic Medicine 71, 106-114 (2009).
6. Perlman, D. M., Salomons, T. V., Davidson, R. J. & Lutz, A. Differential effects on pain intensity and unpleasantness of two meditation practices. Emotion 10, 65-71 (2010).
7. Zeidan, F., et al. Brain Mechanisms Supporting the Modulation of Pain by Mindfulness Meditation. The journal of Neuroscience 31, 5540-5548 (2011).
8. Moulin, D. E., Clark, A. J., Speechley, M. & Morley-Forster, P.K. Chronic pain in Canada- prevalence, treatment, impact and the role of opioid analgesia. Rain Res Manag. 7, 179-184 (2002).
9. Institute of Medicine (US) Committee on Advancing Pain Research, Care, and Education. Relieving Pain in America: A Blueprint for Transforming Prevention, Care, Education, and Research. National Academies Press (2011).
10. Malloy, K. M. & Milling, L. S. The effectiveness of virtual reality distraction for pain reduction: A systematic review. Clinical Psychology Review 30, 1011-1018 (2010).
11. Agency for Healthcare Research and Quality. The Effectiveness and Risk of Long-Term Opioid Treatment of Chronic Pain. Research Protocol. Published 2013. http://effectivehealthcare.ahrq.gov/index.cfm/search-for-guides-reviews-and-reports/?productid=1837&pageaction=displayproduct
12. Best, M. & Neuhauser D. Henry K Beecher: pain, belief and truth at the bedside. The powerful placebo, ethical research and anaesthesia safety. Qual Saf Health Care 19, 466-468 (2010).
13. Beecher, H.K. Pain in men wounded in battle. Ann Surg 105, 123-196 (1946).
14. Wallace, R. K. Physiological effects of transcendental meditation. Science 167, 1751-1754 (1970).
15. Kabat-Zinn, J. An Outpatient Program in Behavioral Medicine for Chronic Pain Patients Based on the Practice of Mindfulness Meditation: Theoretical Considerations and Preliminary Results. General Hospital Psychiatry 4, 33-47 (1982).
16. Zeidan, F., Grant, J. A., Brown, C. A., McHaffie, J.G. & Coghill, R.C. Mindfulness meditation-related pain relief: Evidence for unique brain mechanisms in the regulation of pain. Neurosci Lett 502, 165-173 (2012).
17. Veehof, M., Oskam, M.J., Schreurs, M.G. & Bohlmeijer, E.T. Acceptance-based interventions for the treatment of chronic pain: a systematic review and meta-analysis. Pain 152, 533-542 (2011).
18. Chiesa, A. & Serretti, A. Mindfulness-based interventions for chronic pain: a systematic review of the evidence. Journal of Alternative and Complementary Medicine 27, 9 (2011).
19. Grant, J.A., Courtemanche, J. & Rainville, P. A non-elaborative mental stance and decoupling of executive and pain-related cortices predicts low pain sensitivity in Zen meditators. Pain 152, 150-156 (2011).
20. Grant, J.A. Meditative analgesia: the current state of the field. Ann. N. Y. Acad. Sci. 1307, 55-63 (2014).

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