Lecture 7 - Meditation and Pain

what is pain?

a feeling resulting from injury, linked to the healing process, it can be studied relatively easily, the feeling lasts as long as the tissue disruption lasts, also defined as a feeling that injury has occurred (outlives the healing process), it can extend beyond the healing process, its a private experience and hard to study objectively (doesn’t overlap with an injury), it allows us to identify and withdraw from danger which is why its conserved

insensitivity to pain

a serious condition so you’re in more danger without pain cause you can’t sense danger, causes higher frequency of injury and early death rate, injuries process significantly and become more severe before being noticed, extraordinary vigilance is required

acute pain

brief and overlaps with healing process following injury

chronic pain

persistent so more than 3 months, persists beyond the healing period for injury, includes more disorders

lower back pain

the most common type of pain

role of injury

pain is gonna change the nervous system, it is responsible for sending signals that are responsible for causing pain, what if you change the signaling system to change activation of the response, entry rewires system for signaling pain

allodynia

lowered threshold, innocuous stimuli elicit pain

hyperalgesia

noxious stimuli elicit enhanced pain

spontaneous pain

recurring pain without an identifiable stimulus

chronic pain problem

widespread and more severe, 20-40% lifetime prevalence, associated with reduced quality of life, poor mood (anxiety/depression), impaired sleep, impaired memory and reduced employment functioning, one of the highest economic costs, pain issues are hard to control, intensity of the pain affects quality of life, mood, etc

chronic pain by age group

rate increases significantly with age, it is higher in low income, obesity and women, even when we use animals, we use the male ones causing severe understudy in women, committing error of generalization, important physiological differences between men and women

impact of pain

disrupts mood and lifestyle, tests for assessing impact vary by age group, illness (back pain, leg pain, dementia, etc) and verbal proficiency

pain treatment issues

hard to treat, 50% of patients do not feel pain is properly controlled, its not that pain relieving drugs don’t work but rather they come with a lot of serious drawbacks, many pain-relieving drugs like analgesics/opiates carry risks of use disorder, overdose and tolerance, particularly in severe cases there is an interest in complementary alternative medicine (CAM)

complementary alternative medicine (CAM)

15-20% of chronic pain, patients try CAM therapies, 40% would try meditation, major reasons ppl come to meditation is because they have a pain related problem and they cant treat it easily

meditation in CAM

people with more neuropsychiatric symptoms so that are more likely to experience pain are more likely to seek out meditation

measuring pain in the lab

challenging, it is a private experience inferred via self report, a painful experience might have many features or dimensions of pain (threshold/sensitivity, intensity and unpleasantness), we can use specific tests to examine each one

threshold

point in a stimulus gradient at which pain is first experience (temperature at which you report pain for example), experimentally determined by exposing people to stimuli of varying intensity, a low threshold means that weak stimulus induced pain (same as high sensitivity), the auditory threshold for pain is 130db, no pain is experienced below that

sensitivity

inverse of threshold, so if you have a low threshold you are very sensitive to pain and vice versa

intensity

strength/magnitude of a painful experience, low intensity ratings reflect very little pain, via pain intensity rating scales, different scales for different groups, with kids you have to measure intensity with physiological responses

unpleasantness

the emotional quality we attach to a painful experience, a painful stimulus could be rated as slightly, very or extremely unpleasant or some might say its pleasant, this is assessed via self report unpleasantness scales

treatment effects on pain measures

the effect of treatment on pain measures varies, effective quality of pain is most likely to change with meditation which is associated with mood

distraction

may reduce the intensity of pain, less significant effects on the unpleasantness, if i distract you the pain seems less intense

positive mood

may reduce unpleasantness, less significant effects on the intensity

differential sensitivity

includes distraction and positive mood having different effects on pain, shows that intensity and unpleasantness can be dissociated

cognitive factors affecting pain

meaning of pain, view of self, coping skills and strategies, previous treatment, attitudes and beliefs, factors influencing pain

behavioral factors affecting pain

communication, interpersonal interaction, physical activity, pain behaviors, medications, interventions and sleep

sociocultural-ethnocultural factors affecting pain

family and social life, work and home responsibilities, recreation and leisure, environmental factors, attitudes and beliefs, social influences (ex; in certain communities like athletes, pain is the goal, no pain no gain)

affective factors affecting pain

mood state, anxiety, depression and well-being

sensory factors affecting pain

intensity, quality and pattern

physiological factors affecting pain

location, onset, duration, etiology and syndrome

pain catastrophizing

involves describing pain in more exaggerated terms, ruminating on pain excessively, feeling more helpless about pain than is typical, this results in brain being reported as more intense and distressing than expected, may interact with mindfulness, reducing it is associated with better treatment outcomes

appraisal

how we frame things cognitively

pain processing pathway

nociceptive signals is the same as pain related signals, the info is sent to the spinal cored then into the brain where pain experienced is generated, signal comes from peripheral tissues, brain in meditators is the most studied part of the nervous system

pain matrix

includes the insula, anterior cingulate cortex, somatosensory cortex and prefrontal cortex, variations in these regions are linked to individual differences in pain and chronic pain disorders, all these regions exhibit meditation induced neuroplasticity

how does pain get signaled after the cortex?

goes to the dorsal column nuclei then the A-alpha and A-beta fibers, then finally reaches the primary afferent nociceptors and the C or A-delta fibers

meditation and pain

pain reduction has long been a purported benefit of meditation but evidence for the effect has only been obtained recently, now one of the major recognized treatment indications of meditation, next to anxiety/depression, early studies demonstrated that transcendental meditation may reduce acute pain and mindfulness stress reduction may help manage chronic pain

meditation in treating pain

better than no treatment at treating pain, active control comparisons are less favorable, lack evidence based treatment comparisons due to pharmacological interventions, effect size is small to moderate

general trends

in general, meditation is associated with pain unpleasantness or related measures, effects on intensity and threshold/sensitivity more rare, studies in zen meditators show a somewhat different pattern and are an exception, long term zen meditation show changes in threshold, intensity and unpleasantness of pain

zen meditation and pain

before mindfulness, intensity and unpleasantness are higher, after a mindfulness session they are lower

controversies of meditation pain studies

duration of pain relief is unclear, investment for pain relief is unclear, studies of experimentally induced pain in healthy subjects are common, but may not generalize to chronic pain patients which we want to understand, to be confident of meditation’s effects, we need more experiment studies on chronic pain

meditation effects on pain

changes breathing, prevents catastrophizing by changing cognitive relationship with pain, reducing anxiety/depression via neuroplasticity in networks involved in mood regulation, changing pain related processing via neuroplasticity in the pain matrix, affects endorphins but this is controversial

meditation effects on breathing

breathing affects pain and changes in meditation, factoring out the influence of breathing removes the effects of meditation, the results of this study explain why pain changes around a meditation session (acute effects)

cardiovascular system component in breathing effects in meditation

higher high frequency heart rate variability during meditation is more strongly associated with lower pain unpleasantness

meditation effects on catastrophization

by encouraging non judgmental acceptance, mindfulness may reduce catastrophization, effects on mindfulness and MBCT is greatest in those with high levels of catastrophization

mood improvements

anxiety and depression are frequently comorbid with pain and may complicate its treatment, meditation may help treat pain by treating these conditions (including neuroplasticity)

pain related plasticity

ACC and somatosensory cortex 2 are thicker in long term zen meditators, thickness is correlated with sensitivity, activation of these regions during pain also changes, experts show reduced unpleasantness but not intensity, experts also differ in pain processing as they have reduced activity in S2, al, aMCC, mindfulness is associated with changes in unpleasantness, anticipatory anxiety and PFC activity which contributes to pain

how much meditation is needed to reduce pain?

short term benefits are possible, length of practice is associated with greater effects on activity in the PFC and ACC which are part of the pain matrix, practice time varies between different meditation studies, variability could explain some inconsistencies in neuroimaging studies, though many studies report the same network of structures is affected being the insula, ACC, SS and PFC, the direction of effect varies between studies as increases and decreases have been reported

other mechanisms for pain management

meditation may treat pain by enhancing the body’s natural physiological system for pain management being endorphin transmitters, endorphins act on opioid receptors to reduce pain, if endorphins were key to the effects of meditation, the analgesic effects of meditation should be abolished by a blocker of opioid receptors like naloxone, the evidence for this is mixed so this theory is not widely accepted

placebo effect

any effect of a substance that cannot be attributed to its active ingredients, when a treatment with no active ingredients works its due to this effect, expectation is a mechanism of this

expectation

plays an important role in the effects of meditation and many people approach the practice with pre-existing beliefs about its effects

meditation vs placebo

meditation may have a placebo effect on analgesia, if we want to know the answer to this question, we can compare the two in a controlled study using placebo groups, meditation has stronger effects on intensity and unpleasantness than placebo, mindfulness has greater effects on the anterior cingulate, anterior insula and OFC than placebo which are regions involved in cognitive evaluation of pain, other studies have show that placebo effect can be reversed by naloxone but the effect of mindfulness cannot