Pain: Psychological Correlates 1

By Dr.Thilini Rajapakse, Dr. Dilani Wijeratne

and Dr. Ranjith Pallegama

 

Introduction 

     Pain is a complex emotional experience and not merely a simple physical sensation. Pain has been defined by the International Association for the Study of Pain (IASP) as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, and described in terms of such damage". A thorough understanding of the complex nature of the pain experience (especially the chronic pain experience) will let clinicians appreciate the fact that they should attend to patients with a broad and open mind and avoid “one size fits all” approach in management.

     Clinically, chronic/ persistent pain conditions are the scenarios where pain exists for days, months or years, and may arise from ongoing inflammatory conditions (inflammatory pain) or due to injury to the peripheral or central nervous system (neuropathic pain). Psychosocial issues are more related to chronic pain conditions due to the ongoing nature of the symptoms and suffering.

     A particular stimulus will be perceived as painful depending on the nature of the stimulus and the overall context within which the stimulation occurs, and the pain experience is often influenced by past memories, current emotional state and mood. Hence, the perception of pain is thought to be a multidimensional experience, having physiological (somatic), social or environmental (e.g., support system, societal response, presence of significant other), and psychological (e.g., associated cognitions and emotions) components.

     In the following sections, the relationship between pain and emotion, reasons as to why chronic pain conditions are associated with depression, and other psychological issues related to chronic pain will be discussed.

 

Pain and emotion

How is pain and emotion connected?

     Think about a time when you yourself experienced an acute severe pain.  It could have been due to any reason- e.g., an injury, a toothache, or even broken bone.  Was it a pleasant experience, or an unpleasant experience?  Looking back at it now, would you willingly undergo that same pain experience again?   Or would you do your best to avoid it?

     Most people would describe their experience of physical pain as ‘unpleasant’- and in the case of severe pain, the experience would be more than unpleasant, it could be extremely distressing.  One of the integral aspects of physical pain is that it always associated with an unpleasant emotional reaction. So much so that the International Association for the Study of Pain (IASP) in their definition, describes pain as an “unpleasant sensory and emotional experience”.

     This ‘emotional aspect’ of pain is an important feature that makes it stand out from other sensations, e.g., such as touch.  And it is this unpleasant emotional component of pain which makes it so difficult to tolerate; this is why, as individuals we attempt to avoid pain, and as clinicians we endeavour to reduce the suffering caused by physical pain.

 

Pain and emotion – the biological basis

     The afferent ascending pain pathway has been described in previous chapters.  When the ascending pain pathways are activated, and the pain sensation is localized at the level of somatosensory cortex. 

     But how then, does activation of the ascending pain pathways lead to an unpleasant emotional experience?

     The inevitable association between pain and emotion occurs due to associations between the ascending pain pathway, and the limbic system of the brain.   The limbic system is made up of a group of neuronal grey matter situated deep within the brain, and a rim of cortical tissue around the hilus of the cerebral hemisphere.  The limbic system is an older part of the cerebral cortex. The functions of the limbic system in humans are complex, and one important function relates to the experiencing of emotions, such as fear and anger.

     When the ascending pain pathway passes through the thalamus, it also has connections with the limbic system of the brain.  Therefore when the ascending pain pathway is activated, the limbic system is also activated, which results in the emotional component of pain.

 

Psychological state and pain

     Just as pain causes an emotional experience, the emotional state of a person also can influence the way pain is experienced.  An obvious example is that of a sportsman who sustains an injury during a match, but is able to carry on playing without noticing the pain; he notices the pain only after the match.  A likely mechanism for this ‘reduced’ experience of pain is the release of endogenous opioid peptides (such as endorphins), in situations of heightened arousal.  As discussed in previous chapters, opioid peptides cause inhibition of the ascending pain pathways by activating the descending inhibitory pain pathways.

 

Pain in depression  

     Can the emotional state of a person also increase or worsen the experience of pain?  Again, the answer is most definitely, yes.  Patients suffering from a major depressive episode are more likely to report pain symptoms.  A WHO study conducted over a two year period in 14 countries reported that about 60% of patients with depression presented to primary care clinics with somatic symptoms.  Clinical experience suggests that pain symptoms such as headache, backache, and body aches are commonly reported by depressed patients in Sri Lanka too.

     Recent evidence point to the likelihood that increased pain sensitivity in depression has a biological basis.  Depression is associated with reduced monoamine neurotransmitter levels in the brain, particularly serotonin. Serotonin is also a main neurotransmitter in the descending inhibitory pain pathways.  It is thought that the change in serotonin neurotransmitter levels is likely to be contributing to the increased pain perception reported by patients with depression.  Elevated blood levels of cortisol and inflammatory cytokines seen in depression may also contribute towards increased pain sensitivity in these patients.

 

The role of expectation and anxiety in the experience of pain

     Neuroimaging studies suggest that even in non-depressed subjects, the expectation of pain, and the conviction that pain will occur, can increase the subjective sensation of pain.  The expectation of pain appears to exert a direct priming affect on certain areas of the limbic system, leading to increased experience of pain.

                                                                                     

Summary and Clinical Implications

Pain is defined as an unpleasant sensory and emotional experience. Emotion is an integral part of the experience of pain, and this is secondary to the associations between the thalamus of the ascending pain pathways, and the limbic system in the brain.

The emotional state of a person can influence how a person experiences pain.  In situations of high arousal, pain maybe felt ‘less’; this is likely to be due to opioid peptides acting on inhibitory descending pain pathways of the spinal cord.

Patients suffering from a major depressive episode may experience more pain symptoms.  This is probably due to changes in the neurotransmitter systems in depression- particularly reduced serotonin levels, a neurotransmitter which also plays a role in the descending inhibitory pain pathways.

In any individual, the expectation of pain – for example the expectation and anxiety about pain due to an impending surgical procedure- can result in increased levels of subjective pain being reported by the patient. Psychological interventions have been shown to be effective and important in reducing pain symptoms. 

In a clinical setting, even basic psychological support, such as reassurance, provision of information and giving the patient a sense of control over events, is likely to be helpful in reducing the degree of pain experienced by the patient.

 

Figure 6:  An illustration to show associations between the ascending pain pathway and the limbic system