The Science behind the Silence

The Science behind the Silence: The Use of Meditation in the Management of Chronic Pain

Andrew Gibson Third Year University of Liverpool School of Medicine Word Count: 2,652

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The Science behind the Silence

“If you are distressed by anything external, the pain is not due to the thing itself, but to your estimate of it; and this you have the power to revoke at any moment.” “You have power over your mind - not outside events. Realize this, and you will find strength.” Marcus Aurelius Introduction

The premise is simple. If you think hard-enough the pain will go away. These words spoken by the philosopher and sixteenth emperor of the Roman Empire may be interpreted as rather inconsiderate to someone suffering from chronic pain. Surely one who experiences pain for long periods knows their condition better than anyone, and believes it is not a figment of their own estimation that they have to endure? However, Aurelius was not speaking of 'normal thought' as we know it, but of the benefits of meditation.

Meditation is mental skill that increases the user’s sense of awareness, attention and regulates emotions. The overall goal, if it can be called that, is to improve the meditator's well-being. The earliest recorded form dates back to BCE 1500 in the Hindu tradition of Vedantism, or scriptures known as Vedas (1). Here the practice of meditation, or Dhyana, consists of fully immersing and concentrating the mind on a subject, and excluding all other thoughts and ideas. It is one of the eight aṣṭāṅgas (limbs or branches) of Yoga. (2) Around one thousand years later, other meditative practices emerged such as Taoism in China, from which the martial arts Tai Chi and Qi Gong emerged. Since then, numerous religions have conceived their own brands of meditation and various sub-types exist to this day. Two similar variants that will be considered in this essay include Mindfulness and Zen.

Zen is centred around direct focus of the mind, typically on the user's breathing, with some schools regarding it as a method of considering the nature of our very existence. Mindfulness provides a much less existential direction for the meditator. Mindfulness involves the individual becoming consciously aware of the present moment and non-judgmentally accepting all thoughts which enter the mind. A recent explosion in the interest of mindfulness can be attributed to Professor Jon Kabat-Zinn, who developed the mindfulness based stress reduction (MSBR) program. This program has been taken up by hospitals and other institutions across the world to help people cope with stress, anxiety, illness and pain. In essence, it is the lack, rather than the use of thought, that produces the effects of meditation.

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The Science behind the Silence

Today, meditation has been adopted in some form by all of the major religions. It has also been implemented in many non-religious practices, notably in the management of chronic pain. It is categorized by the National Health Service as an alternative or complementary form of Medicine, alongside its relatives Tai Chi, Yoga and Qi Gong. In the past twenty years, much research has gone into determining the mechanisms of pain relief that meditation provides. This essay will consider current theories on how the brain processes pain sensations, along with how meditation structurally changes the brain and alters pain tolerance. How meditation assists with the emotional burden of suffering with long term pain will be discussed. Finally, the current place of meditation in western health care will be evaluated.

Brain and Pain

Pain is a vital function in the natural world, warning an organism about actual or impending tissue damage and allowing for subsequent escape from insult. However pain becomes problematic when the sensation persists without actual harm. The manner in which pain is processed from stimulus to perception is a complex subject which is not yet fully understood. Since the inception Engel's biopsychosocial model in 1977, medicine has accepted that pain is not just a biomedical mechanism independent of the mind. Pain interpretation is dependent on the sufferer's perception (3).

In 1983, Leventhal et al suggested the dual process theory of pain to rationalize how the mind manages pain. The first aspect is based around the “objective-cognitive” processing of pain. That is to say, appraising the size and threat of a pain stimulus by using prior knowledge and memories, in accordance with the level of the stimulus. The second facet is based around the “subjective-emotional” processing of pain. In other words, how the person thinks about the pain, and the emotions it stirs up such as fear, anger and depression. (4) Since the introduction of Leventhal's theory, it has been demonstrated that these two processes are non-linear. A relatively small pain stimulus may conjure a large and devastating emotional response from a certain individual. Conversely, large pain stimuli may elicit a modest emotional response (5). Whether this is due to genetic or psychological tendencies is unknown, and reminds us that we are all intrinsically different.

The functional anatomy of the pain signalling networks has been mapped comprehensively. It begins as tissue damage releases substances known as pain mediators, which are detected by specialised sensors called nociceptors. From the nociceptors, pain signals are sent towards the brain along two main types of nerve fibre.

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The Science behind the Silence Aδ fibres are myelinated and quickly conduct the instant sharp sensation. C fibres are unmyelinated and transmit a slower throbbing sensation following injury. These nerves enter the dorsal horn of the spinal column, and decussate shortly after. Pain is carried up the spinal column in two tracts; it is here where the precise mechanism of pain perception becomes more obscure. The Spinothalamic tract synapses in the thalamus and continues into the somatosensory cortex. It is mainly involved in pain localisation. The Spinoreticular tract ends in the thalamus and hypothalamus and is active during the emotional processing of pain. Using functional magnetic resonance imaging (fMRI), distinct areas of the cerebral cortex have been mapped which are also associated in the pain experience. This collection is known as 'The Pain Matrix' and consists of the anterior cingulate cortex (ACC), insula, PAG (Periaqueductal Grey Matter), two somatosensory cortices (S1 and S2), the prefrontal cortex (PFC) and the amygdala. (6) A simplified summary of these networks is shown in figure 1. With regards to pain processing, the 'how?' remains unexplained. However since we know the 'where?', we can observe changes to these locations using fMRI under different conditions.

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Figure 1: A schematic showing a simplified version of the pain signalling network. Adapted from 'An introduction to pain pathways and mechanisms', and Human brain mechanisms of pain perception and regulation in health and disease (6)'

The Science behind the Silence

I Feel, Therefore I Think

Interoception is the ability to recognise stimuli originating from inside the body. It can be considered as the sensory component to homoeostasis. In terms of anatomy, it is to the sympathetic system what the IXth and Xth nerve are to the parasympathetic system (7). This is important since the conventional view of stimuli dictates that the distinct, well-discriminated feelings of pain, temperature and itch are associated with an 'exteroceptive system', that is to say, sensitivity to external stimuli. However Craig offers that since lesions in the somatosensory cortex do not abolish pain, this convention cannot be fully true. Furthermore, the subsequent emotional response following a painful stimulus that is not seen during simple mechanoreceptor stimulation necessitates the view for an alternative model. (8)

Herbert et al concluded that those with a greater sense of interoception had greater behavioural self-regulation, therefore linking it with the emotional aspect of pain cognition (9). Pollatos et al went on to demonstrate that individuals with heightened interoception were less tolerant and more sensitive to painful stimuli. (Levels of interoception were measured by asking participants to count their own heart rate by merely sensing it). These studies therefore heavily implicate the interoceptive sense with pain modulation. Although this system remains poorly understood, cortices that have been associated with it include some of those found in the Pain Matrix: AAC, insula, and certain nuclei along the spinothalamic tract. (10)

Meditation versus Misery

In recent years, good evidence has emerged showing how meditation techniques alter pain sensation. These studies can be grouped into those that assess organic functions within the body, relating them back to prior knowledge of pain stimulus and processing. Other research has focused on the way meditation modifies the emotional experience or response to pain. Each of these avenues of research are valuable since as each represents one arm of Leventhal's dual processing of pain.

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The Science behind the Silence Organic Changes

In the last ten years, much work has been carried out to determine how inflammatory mediators are modified by mind body therapies, like meditation. Bower and Irwin reviewed the current literature base, which assessed the effect of mind body techniques such as Tai Chi, Qi Gong, Yoga and various types of meditation on circulating inflammatory markers. Many chronic inflammatory conditions cause long term pain. Markers are a useful tool in tracking inflammation levels and disease severity. The most common marker studied was C-reactive protein. Results were mixed across all mind body therapies, with significant reductions in circulating inflammatory markers in some studies, but not in others. From the evidence, Bower and Irwin postulate that a neuroendocrine mechanism may play a key role in how mind body therapies reduce inflammation. The hypothalamicpituitary-adrenal axis is responsible for the regulation of cortisol. Cortisol is a steroid hormone which regulates inflammation and is believed to be increased in times of stress. Therefore, mind body therapies could in theory reduce stress leading to lower cortisol levels, reduced inflammation and therefore reduce pain (11).

Physical changes to the brain have been observed in meditators by using fMRI techniques. A meta-analysis by Boccia et al outlined areas of the brain that were activated during various types of meditation. They concluded that the caudate nuclei, insula, precuneus, middle & superior temporal gyrus, ACC and claustrum were accessed during meditation. Structurally, increased grey matter volume was seen in the ACC and thalamus, medial frontal gyrus, precuneus, and fusiform gyrus.(12) In other studies, zen meditators have shown reduced activation in the prefrontal cortex, amygdala ACC, thalamus and insula (13). The ACC and insula form the salience network, which functions in the perception and attention of stimuli. Lutz et al showed that mindfulness mediation reduced activity in this area before the painful stimulus was applied. This lead to the conclusion that experienced meditators were able to down-regulate anticipation of a painful stimulus, thereby reducing its overall effect (14).

Overlap can clearly be seen with structures known to be involved in the pain signalling pathway (as mentioned previously), and those that are involved during meditation. The ACC, insula, prefrontal cortex, thalamus and amygdala are used during meditations and in the perception of pain. These areas are also used in evaluation and emotion, furthermore strengthening the association between the two mechanisms. Those with more meditation experience demonstrated greater changes on fMRI. It would appear these brain changes correlate with the core function of meditation, allowing the user to acknowledge the pain, and accept it, rather than block it out altogether (13). This was emulated by Gard et al who found that participants reported no change in

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The Science behind the Silence pain intensity, but a marked decrease in pain unpleasantness. In their study, other organic changes included increased activation to areas associated with interoception during mindfulness meditation, specifically the insula. They offered that this allowed the user to, in accordance with mindfulness, cognitively disengage themselves from the painful stimulus. That is not to say they did not feel the stimulus any less than a control subject, but the stimulus did not carry a greater emotional effect (15).

Unfortunately, these results are difficult to replicate. This is likely due to the highly heterogeneous nature of meditation and its difference between users. Furthermore, participants were subject to acute painful stimuli, a grossly different experience when compared to chronic pain. How organic changed may manifest in chronic pain patients remains unclear. However these studies have nonetheless yielded interesting and exciting results in the way meditation can change the physical structure of pain signalling mechanisms.

Psychological Changes

Despite biochemical and fMRI studies giving us insight into the mechanics of meditation, the external validity of these studies must be brought into question. Whether or not these changes noted on fMRI actually correspond to improved quality of life is key. This is where the psychological changes of meditation are most important. People who suffer with chronic pain often possess depressive, anxious and, fearful mind states. This correlates to the emotional branch of Leventhal's dual processing, exacerbating any pain the person may be experiencing. This often leads to a vicious cycle of pain, low emotions, worse pain, lowering emotions and so on. Meditation has been has been shown to decrease these aspects people who suffer with chronic pain, and break the vicious cycle that perpetuates in many that suffer from it. (16)

Novice meditators who completed a three day course of meditation demonstrated significant benefits. Patients reported reduced pain sensitivity, showing meditation had a significant analgesic effect. This was attributed to participants experiencing less anxiety about the impending pain stimulus, accounted for by anxiety scoring (17). Rheumatoid arthritis patients who underwent Kabat-Zinn's eight week MSBR program exhibited an improvement in overall psychological wellbeing, reducing depression and decreasing psychological distress (18). This signifies that meditation can achieve psychological benefits in a relatively short amount of time, potentially reducing the impact of chronic pain on a person’s life. Kabat-Zinn himself attributes the success of mindfulness in preventing the mind from wandering into negativity (19).

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The Science behind the Silence Meditation and Implementation

All drugs have side effects. In the UK, people coping with pain will most likely find themselves on a certain rung of the WHO pain ladder (20). This includes medication ranging from NSAIDs (non-steroidal anti-inflammatory drugs) which can cause gastric irritation and kidney damage, to strong opioids which cause dizziness, constipation and have addictive properties. Opioid induced hyperalgesia has also been thoroughly discussed (21). Furthermore, other medication may be added to combat these side-effects, resulting in polypharmacy. Thankfully, the analgesic benefits most patients experience from these medicines outweigh the drawbacks.

Meditation by contrast has no side-effects, is virtually cost-free and is available to all ages. However to suggest all patients immediately drop medications in favour of meditation is farcical. Meditation certainly has its limitations. Most of the studies referenced by this text mention that results are difficult to replicate due to the heterogeneous nature of meditation. This means the evidence, exciting as it is, carries little weight when compared to the vast number of drug trials for analgesics.

Additionally, pain relief therapies must be tailored to the patient with a holistic approach. The effectiveness of meditation depends on the type of patient. Are they motivated and want to be an active participant in their treatment? If so meditation may be an ideal therapy. Or is the patient a bystander and simply wants to take a pill and carry on with their lives? A parent working a full-time job may feel they may not be able to make time for any mind-body techniques in a busy household. As mentioned previously, meditation is listed as a 'complementary and alternative therapy' in the NHS. For people with chronic pain, meditation appears to be best used as a complimentary therapy to pharmacological treatments (as opposed to an alternative treatment). An ideal implementation would allow patients to experience less distress, potentially reducing their required dose of analgesia to find comfort, thereupon reducing patient exposure to side-effects and reducing overall cost. A study that assesses combined pharmacological and mind-body therapies against stand-alone pharmacological therapy in a randomized controlled trial could pave the way for mainstream use of mediation in healthcare.

Meditation has been shown to reduce the psychological impact of pain. The intriguing results from fMRI studies also mean that the use of meditation is not merely mind over matter, as Aurelius said. Rather, it is having the mind to change the matter altogether. With mindfulness and other mind body techniques gathering momentum, meditation may become a first line therapy for chronic pain in the future, shifting the stereotype of meditation from the monk to the medic.

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The Science behind the Silence

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