DECONSTRUCTING PAIN PERCEPTION THEORIES - CAN PHYSICAL PAIN BE BLOCKED OUT? (PART 2)

Medically Reviewed by Dr. Sony Sherpa, (MBBS) - September 24, 2024

The following article forms the second part of a discussion on what pain is and how it can be blocked out in the most effective way possible.

Theories of pain are reviewed in part 1, including the biopsychosocial theory, which is the most recent and all-encompassing. Part 2 below expands more on this theory and provides suggestions for long-term biopsychosocial pain management.

Expansions on the Biopsychosocial Theory of Pain: Supporting Evidence

Research has further expanded on the biopsychosocial theory of pain by fleshing out aspects of the mind-body connection in more detail. Some of the highlights of this research are summarized below:

Pain in the Brain

The neuromatrix of pain has been further divided into several distinct networks, the most well-known of which might be the ascending and descending pathways to pain:

• Ascending Pathways to Pain. Pain-related signals from the periphery inform the brain via the spinal cord. On their way “up”, they activate the ascending pathways to pain, which are known to generate the experience (as opposed to inhibit it). These ascending pathways are often divided into the following two lesser brain pathways:
  • The Medial pathway refers to the anterior cingulate cortex and the insular cortex. These code sensory information, including painful sensations, sympathetic nervous system function (stress response), as well as emotional, social, and cognitive processing. These processes interact to give rise to the discomfort associated with pain, as well as the way in which it is perceived in relation to the self.
  • The Lateral pathway extends to the somatosensory cortex and parts of the parietal lobe. This pathway is responsible for coding fine details pertaining to painful sensations, such as intensity, localization, and the specific type of pain felt.
• Descending Inhibitory Pathway to Pain. This pathway serves to balance the other ascending pain pathways through inhibition, consisting of the amygdala, a different part of the anterior cingulate cortex, the periaqueductal gray, the parahippocampus, the hypothalamus, and areas of the brainstem (which ultimately feed to the dorsal horn in the spine and then the periphery). It is responsible for putting an end to continuous pain, for context-dependent pain processing, and for placebic pain relief, highlighting how some pain can be either blocked or promoted through one’s interpretation of the painful stimulus. Chronic pain is theorized to be the result of a deficit or dysfunction in the descending inhibitory pathway of pain. This pathway is thought to be governed mainly by noradrenergic and serotonergic neurotransmission (linked with stress, arousal, and mood states). However, it can also be stimulated by dopamine (with respect to the prefrontal cortex and reasoning), several other neuropeptides, and opioids.

Different pain treatment and management approaches tend to inhibit different aspects of the ascending and descending pathways to pain, which may make each approach either more or less appropriate to an individual, depending on the cause.

Neuro-Psychological Inputs

In addition to the ascending and descending pathways to pain, the mind makes its own contributions toward processing or perpetuating pain in both the brain and body. These include the mental, emotional, and social inputs briefly detailed below:

• Pain-Related Association and Memory. Further research has highlighted how pain and its emotional components can go on to create memories that are associated with neural networks. Like any kind of practiced skill, these neural connections can become more developed over time the more the same type of pain is encountered alongside the same response towards it. In those with chronic pain, these networks are believed to be much stronger than in the average person, often able to trigger or amplify pain without an apparent cause or in response to ordinary stimuli that may be inadvertently associated with a past memory of pain. Other factors may form part of these neural connections and contribute towards perpetuating or amplifying signals of pain, including immune, endocrine, cardiovascular, emotional, and social factors, as discussed below.
• Stress, Emotion, and Mood. Pain shares a direct relationship with stress, fear, and panic, as well as the negative emotions associated with these. Nociception is often able to trigger the stress response in the body, which can be amplified by mental-emotional stress (anxiety) that can promote increased pain perception and intensity. The stressful and emotional components of pain help to create a memory that tends to promote future avoidance of pain, which is associated with the threat. Fearful memories of pain can also contribute to amplifying future pain. Regulating one’s mood can help to reduce the perception of pain and suffering in response to it, even if the body becomes stressed as a result of a painful stimulus.
• Cognition and Perception. Many ways of thinking affect overall perception and have been shown to enhance emotional regulation, with pain being no exception. The way one thinks of pain sets the tone for one’s connection with it, which can both increase or decrease the way in which it is experienced. In this way, pain and the response towards it are learned phenomena different from nociception. Positive memories, beliefs, and mental associations can serve to change one’s concept of pain, regulate one’s mood, and moderate one’s relationship with pain for the better.
• Pain catastrophizing is linked with increased pain perception^[1], amplification, and activity in pain-related brain networks, which are far more pronounced in patients with chronic pain.^[2] 28-40% of pain-related disability is said to correlate with suffering and pain catastrophizing, compared to the 0-3% correlation seen with enhanced pain intensity.^[3] Examples of negative thoughts that consist of pain catastrophizing include excessive thinking about pain, exaggerating the outcomes associated with the pain, and asserting to oneself that nothing can take the pain away. Positive personality traits such as self-efficacy, optimism, and hope were shown to guard against pain catastrophizing, reduce pain intensity and interference, and promote a higher tolerance for pain.^[4] While these traits are often thought to arise in response to positive emotion and an absence of pain, they can be strengthened through reflecting upon oneself, focusing on them, meditating, and understanding pain.
• Social Influences. Cultural and social conditioning largely contribute to the way in which we perceive and experience pain. Studies have shown that perceived injustice and stigmatization with respect to pain can increase its perceived intensity and substantially inhibit the healing process. These are greatly enhanced by social support, social standing, and similar related influences. Furthermore, socializing itself represents an important buffer against stress that enhances motivation, aids recovery from injury, and can further reduce perceived pain intensity as well as moderate negative pain-related behaviors. Pain appears to also be associated with antisocial behaviors and withdrawal. As a result, pain can be amplified by prolonged social isolation and exclusion where social support is withdrawn.^[5] Studies show that these are associated with a higher degree of pain interference, lower pain thresholds, and greater experiences of pain intensity.^[6]

Physical Inputs

In addition to the brain and mind, which are arguably responsible for generating the bulk of our pain, the body also makes several contributions toward pain processing:

• Spinal Column Neural Networks. Just like in the brain, the nervous system in the spine is capable of creating its own neural networks pertaining to pain as well as movement and other physical sensations. Those with chronic pain have been shown to develop projections of nerves from the spinal column that can perpetuate and amplify signals of pain, serving as extensions of pain processing in the brain.
• Peripheral Nociception. The skin has a distinct type of neuronal fiber (A delta fibers) involved in detecting pain in the muscles and internal organs (C fibers). These fibers send sensory information to the spinal cord when alerted by affected cells. Cells contain thousands of receptors that can be activated by temperature, touch, or pressure in the skin, as well as chemical stimuli in the muscles and organs. Due to nerve fiber differences, painful sensations from the skin are often more specific, short-lived, and felt as sharp, itching, or burning, while the pain from the organs and muscles is often less localized and duller.^[7]
• Inflammation. During injury, the immune system becomes active in localized damage control and wound healing. Injury often triggers inflammatory compounds (cytokines), stress hormones, growth factors, neuropeptides, a higher degree of acidity at the injury site, as well as chemicals, temperature, and touch receptors, depending on the nature of the wound. Combinations of these chemical compounds can be enough to trigger nociception in either the brain or the periphery. Neuroinflammation (in the central nervous system) is also known to heighten pain processing, as well as neuroexcitation, and may be triggered by inflammatory stimuli in the body or brain. It may also result from prolonged negative emotion or ideation. In certain inflammatory diseases and other conditions such as allergies, inflammation can cause generalized pain through association, even in the absence of a true painful stimulus.
• Nerve Conduction and Excitation. The sensation of pain also depends on the balance between nerve excitation and inhibition. Overstimulation of nerves is associated with a higher degree of experienced pain and intensity, while lower stimulation and slow nerve conduction are associated with a lower perceived pain intensity, a higher pain threshold, and better tolerance. If peripheral signals are weak (lacking enough excitation), then they may terminate in the spine before being processed by the brain or occur to the individual as an itch. Heightened excitation from pain processing centers of the brain can also mediate an increase in peripheral pain without nociception. This is normal during hyperalgesia, where tissues surrounding an injury become sensitized and painful. However, it tends to occur chronically in pain disorders and is associated with a loss of function in the descending inhibitory pathway. Excitation may be enhanced through imbalances in glutamate expression, states of arousal, and electrolyte levels, while inhibition may be enhanced via GABA transmission and optimal potassium status.

Other Factors that Influence Pain Perception

The way in which one processes and perceives pain is affected by overall health and metabolism. In line with this understanding, some of the below factors are known to further influence the experience of pain:

• Insulin Resistance and Excessive Body Fat. Increased stress levels, hyperglycemia, increased sensitivity towards pain, a prolonged pain response, and higher pain interference levels are associated with obesity and insulin resistance. ^{[8] [9]} Animal studies have revealed that fructose-induced insulin resistance is capable of creating neuropathic pain in which nerves signal for pain in response to non-painful stimuli.^[10] Insulin resistance is also known to occur during severe acute states of pain and stress, possibly sharing a close relationship with pain processing.^{[11] [12]}
• Sleep Deprivation. A lack of sleep is linked with many factors that can increase sensitivity towards pain, such as higher anxiety levels, inflammation, a worse mood, and reduced cognition. Preliminary evidence suggests that complete sleep deprivation may reduce the pain threshold in healthy individuals and increase perceived pain intensity in those with chronic pain disorders. Partial sleep deprivation may increase pain intensity perceived in response to spontaneous pain. Fragmented sleep may be worse than sleep deprivation, as it is associated with reduced pain thresholds and tolerance, as well as heightened sensitivity. Interestingly, selective sleep deprivation in a positive context (e.g., staying up all night for a party) had little to no effect on pain perception, tolerance, or intensity. ^[13] Females may be more sensitive to the “pain-promoting” effects of sleep deprivation.
• Circadian Signalling. The expression of chemicals, hormones, cytokines, and neurotransmitters all fall in line with the body’s circadian rhythm. This serves to increase or diminish painful sensations throughout the day and night, depending on the type of pain and the context. Those with inflammatory autoimmune conditions like rheumatoid arthritis have been shown to experience worse stiffness in the morning, in line with the circadian peak in metabolism. This improves when immune-suppressing medications are taken the night before compared to if they are taken in the morning when the symptoms are experienced.^[14] Light exposures also have a profound impact on circadian signaling and pain sensitivity, with the light of different wavelengths (and colors) showing promise for pain relief.
• Gender. Women are known to experience a higher degree of pain than men due to having lower pain thresholds and tolerances on average, as well as experiencing higher pain intensity and exhibiting a larger stress response towards pain than men. These findings have been attributed to differences in genetics, reproductive hormones, brain pain processing, immune function, and sociocultural norms.^[15]
• Aging and Pain Sensitivity. The aging process may affect pain perception. In an overview of studies investigating pain perception in older adults and the elderly, low-intensity pain thresholds were shown to increase with age. However, overall pain tolerance diminished.^[16]

How to Block Out Physical Pain (in Theory)

While it may seem daunting in some scenarios, pain can be effectively blocked out in a way that sees lifelong benefits. This is achievable by taking all the biopsychosocial components of pain into consideration. This form of pain management has been estimated to be 21 times more cost-effective than other current treatment methods that only truly treat nociception.

The following suggestions may help improve pain perception and tolerance. However, effective lifelong pain management can only be made possible when the individual and their circumstances are taken into consideration.

For more medical pain management solutions, contact a medical expert.

Abolishing Pain Resistance. Pain is a necessary requirement for healing to take place. Blocking it out completely ignores its prime benefit as a signal for injury or harm. Instead of fearing pain, which can increase its perceived intensity, it is useful to abolish any resistance toward the experience. This can be achieved through lowering stress, rethinking a painful situation, or distracting from the pain. All these methods can have a profound impact on both ascending and descending brain pathways to pain:

• Breathing and Meditation. Meditation is known to have a positive effect on many areas of the brain, including the insular cortex and amygdala. In theory, consistent mediation can lessen pain-related associations by reducing stress (particularly when coupled with deep breathing), putting a pause on memories and associations capable of amplifying pain, as well as having a positive effect on one’s perception of self and connection to the world at large. This, in turn, promotes a positive self-image, improved mental health, and better social functioning. Other studies have confirmed that meditation is capable of regulating excitatory brain activity in pain-processing areas and is associated with reduced pain intensity and unpleasantness.
• Cognitive Reappraisal and Perception. Positively changing one’s perception of a painful stimulus can help to regulate one’s mood, minimize suffering, reduce associated inflammation, and may help to lower its perceived intensity. This can also serve to improve personal resilience by emphasizing an approach to pain that supports self-efficacy and the ability to cope without requiring any external input. In line with these observations, Psychotherapy has been shown to moderate pain in those with depression and other similar disorders by promoting activity in the anterior cingulate cortex and the descending inhibitory pathway. This has been shown to be effective in approximately 50% of patients, which may pertain to the functioning of this brain area.
• Shifting Attention to Something Else. Constant rumination that supports pain catastrophizing, stress, depression, or anxiety does not help to alleviate aspects of pain in the same way as cognitive reappraisal might. Instead, these actions have the opposite result and may serve to enhance pain perception, discomfort, and suffering. If one cannot change to a more positive frame of mind, distracting from these kinds of thoughts can help lower the volume of pain-related brain networks. Physical activity, meditation, breathing, and other hobbies are tried and tested ways for positively shifting one’s attention off painful stimuli and associated thoughts.

Social Support. Individuals who have social support have been shown to experience less pain on average than those without.^[17] This is thought to be related to the stress-buffering effects of social support and possibly oxytocin release as well. Oxytocin, the “trust hormone,” appears to improve connectivity in the medial pathway in anxious or depressed individuals, which can serve to reduce pain catastrophizing, discomfort, perception, and suffering.

Balancing the Metabolism. The balance between pain mediation and relief is governed at a deeper level by cellular metabolism. Regulating the metabolism can help to improve baseline pain tolerance by promoting balanced immune signaling, nerve conductance, mood, cognition, and brain connectivity. The following lifestyle factors help to keep the metabolism stable and promote lifelong pain relief:

• Sleep and Sun. It is important to get a night of good sleep in order to promote emotional stability and optimal neurological function, which encompasses pain signaling and relief as well. Getting enough sun throughout the day serves to stabilize the circadian rhythm and improve melatonin levels^[18], which helps to improve sleep quality, reduce inflammation, and regulate pain-related signaling. Sunlight exposure during the day is associated with a reduction of up to 21% in painkiller requirements for hospitalized patients in recovery.^[19]
• Exercise helps to improve pain thresholds and lower pain intensity in a number of ways, depending on the kind of exercise. It stimulates the descending pain pathway by releasing pain-relieving opioid compounds such as endorphins, anti-inflammatory cytokines, and neurotransmitters such as serotonin.^[20] Exercise can also improve the health and functioning of the nerves in the spinal column, which may help to reshape neuronal extensions from the spine associated with promoting pain, as well as improve the function of the descending inhibitory pathway. Aerobic exercise is known to protect the brain from neurodegeneration, enhance overall cognition and mood, and beneficially activate various brain areas associated with pain processing.^[21]
• Diet. Consuming a whole food plant-based diet high in nutrient-dense fruits and vegetables has been shown to be good for optimal health, well-being, and pain reduction. Specific dietary recommendations for pain management have focused on increasing omega-3 intake, reducing omega-6, refined sugar, and overall fat intake, and focusing on brightly colored foods rich in vitamins, minerals, and flavonoids. B vitamins, vitamin D, zinc, beta-carotene^[22], magnesium, and potassium are associated with lowering pain intensity in those with chronic pain disorders. Magnesium especially serves to lower the activation of glutamate-dependent NMDA receptors, which helps to relax muscles, lower pain intensity, and improve pain thresholds. Some flowers, teas, herbs, and spices with potent anti-inflammatory and immune-regulating properties can also help to moderate pain, such as chamomile, mint, clove, and ginger.^[23]

Other Therapeutic Approaches to Pain Relief. Many other therapies have been developed for pain relief that aim to stimulate pain pathways through tactile stimulation, as described below:

• Temperature. Both heat and cold therapies have been used for hundreds of years in the management of pain and injuries. Each type activates unique receptors in the skin, has unique pain-relieving effects, and is capable of improving pain tolerance.^[24] Cold therapy reduces blood flow, metabolic activity, swelling, and muscle contractions or spasms, while heat therapy improves blood flow, increases metabolic activity, and enhances connective tissue elasticity.^[25] Applying heat may be more beneficial with respect to lower back pain and delayed muscle soreness, while applying cold might show better results in lowering the risk for injury after working out and lowering pain before receiving an injection.^[26]
• Touch. Touch therapy, massage, and reiki have been shown to impart a mild degree of pain relief in recipients. Hand holding, stroking, and gentle touch, also known as affective touch, which slowly and gently stimulates the skin, are known to alleviate pain by activating specific touch receptors. This type of stimulation can activate most brain areas pertaining to pain processing in a way that usually reduces pain intensity, except in some forms of neuropathic pain. The emotional component of gentle touch contributes towards pain relief as well. After a while, gentle touch is also capable of lowering the intensity of peripheral sensations (when touch no longer registers) through inhibition at the spinal cord level, which also dampens down on signals of pain. ^[27]
• Spinal Cord and Transcranial Stimulation. There are several techniques used for pain relief that stimulate the spinal cord and brain, helping to promote the activity of the descending inhibitory pain pathways, reduce inflammation and stress, and promote balanced brain activity in most areas pertaining to pain processing. These techniques include electrical and/or magnetic spinal and transcranial stimulation and acupuncture. Low-level laser therapy can also stimulate the brain and spinal cord in a similar way. In addition, these methods have been shown to improve pain intensity related to the medial pathway, suggesting it can improve personal resilience and reduce the tendency for suffering.

Conclusion

After hundreds of years of investigation, it is now understood that pain comprises biological, psychological, and social components that are unique to every individual.

On the biological level, pain is detected by the periphery, sent to the spinal cord, and if the signal is strong enough, transmitted to the brain for further interpretation. Pain is involved in shaping the quality of memories, and rendering aspects of self-identity. It is also linked to our thoughts, feelings, and stress response, all of which allude to its psychological and social components.

Pain detection can be further moderated through making healthier lifestyle choices, such as meditating, getting enough sunlight, resting well, consuming a plant-based wholefood diet, and participating in regular exercise. In addition to these, touch-based therapies that stimulate the nervous system have shown great promise in strengthening the physical control mechanisms designed to control and inhibit pain.

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