Where Does Pain Come From?

[Part 1 of a two part guest post from Dr. Pamella Thomas, PRIUM's Medical Director]

What is Pain?

Chronic pain initially begins, appropriately, as acute pain – a biological event in response to noxious stimuli.  However, as time progresses, social, psychological, and cultural factors impede and complicate recovery. 

Pain, generally, is defined by the IASP Task Force on Taxonomy, 1994, as an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.¹  The individual’s experience of pain is mediated by the brain; pain is always subjective.  Commonly the experience of pain is due to physical injury; however, it may also be caused or intensified due to emotional stress: anxiety, depression, exhaustion. The prefrontal cortex of the brain’s frontal lobe plays an important role in interpreting and mediating both types of pain perception.

Role of the Brain

Our understanding of the brain’s role in pain perception has advanced significantly.  For example, we now understand that one's prior experience involving pain, its consequences, and associated moods and stressors, plays an important role in a person’s experience of pain.   One hypothesis is that early adverse experiences and early-onset mental disorders may contribute to a chronic imbalance in hormonal and neurotransmitter mediators linked to neuronal stress response pathways.²  This in turn has been linked to a range of adverse metabolic, cardiovascular, immunological and cognitive effects.^3,4 

Adverse Childhood Events

Additionally we know that adverse experiences with pain occurring prior to age 18 heavily influence our ultimate perception of pain.  Adverse experiences such as abuse, neglect, poverty, parental death, divorce, drug use, and incarceration have been shown in numerous studies to have profound effects on a child’s temperament and psychological and physiological development.

Studies from the Centers for Disease Control and Prevention (CDC) and international surveys from the World Health Organization (WHO) provide mounting evidence and weight to the theory that Adverse Childhood Events (ACEs) predispose a person to poor health as an adult.  Of note, ACEs causing anxiety and/or depression in childhood were positively correlated with chronic pain in adulthood.  Most interestingly, these emotional stressors from childhood are directly correlated with physical disease states in adulthood. Individuals with a history of three or more ACEs were more likely to be diagnosed with each of the six physical conditions measured by the WHO: heart disease, asthma, diabetes, arthritis, chronic spinal pain, and chronic headache.  Those individuals who had suffered from childhood physical abuse had an even longer list of adult chronic disease.

These results suggest that early onset mental disorders may function as endogenous psychosocial stressors that can be associated with poor physical health in adulthood caused not only through increased risky health behaviors, but also through direct biological mechanisms.

Authors KM Scot et al., found in their study, “These results are consistent with the hypothesis that childhood adversities and early onset mental disorders have independent broad spectrum events that increase the risk of diverse chronic physical conditions later in life.”⁵

Anecdotal Experience

As a former medical director overseeing an onsite employer clinic, I had specific insight into the chronicity of some of the workers’ compensation patients filing claims.  Some employees had charts over two inches thick with frequent claims and follow-up visits. I affectionately referred to them as my frequent flyer work comp club members. Given their frequent visits and extensive charts, I began to interview some of these employees and ask questions about their work environment and about their childhood up until 18 years of age. I wanted to see if there were any common experiential themes amongst this population.

I heard frequently from the employees that they had issues with their supervisors or others in authority.  Similarly they had disagreements with those they interacted with at home.  I also frequently heard anecdotally that these employees suffered through poor in-home security, lower socioeconomic status, and circumstances that caused frequent fear and anger in their homes from an early age.

The Doctor-Patient Relationship

Though I likely missed a great opportunity to reproduce the results found in the ACE study, I found that just by taking the time to engage these injured workers in conversation, addressing factors outside those reported as part of the injury, that some seemed to have fewer ongoing problems going forward.  Being heard and validated proved therapeutic for these oft troubled employees.  Actively listening to patients may help prevent chronic pain and its complications from certain treatments. It is my conclusion that the physician-patient relationship should be seen as the critical piece in treating workers’ compensation claims, especially for workers that display a particular subset of characteristics that I will detail in a follow-up post.

1.            Merskey H, Bogduk N. Classification of chronic pain, IASP Task Force on Taxonomy. Seattle, WA Int Assoc Study Pain Press available online www iasp-pain org). 1994.

2.            McEwen BS. Protective and Damaging Effects of Stress Mediators. N Engl J Med. 1998;338(3):171-179. doi:10.1056/NEJM199801153380307.

3.            Miller GE, Cohen S, Ritchey AK. Chronic psychological stress and the regulation of pro-inflammatory cytokines: A glucocorticoid-resistance model.

4.            Chrousos GP, Kino T. Glucocorticoid action networks and complex psychiatric and/or somatic disorders. Stress. 2007;10(2):213-219.

5.            Scott KM, Von Korff M, Angermeyer MC, et al. Association of childhood adversities and early-onset mental disorders with adult-onset chronic physical conditions. Arch Gen Psychiatry. 2011;68(8):838-844. doi:10.1001/archgenpsychiatry.2011.77.