What is chronic pain?
If the model below looks very complex to you - and maybe even a little overwhelming - it's because the reasons why some people develop chronic pain and either respond or don't respond to treatment are incredibly complex. Unlike acute pain, which can act as a helpful warning signal, the experience of chronic pain doesn't seem to have an adaptive function. Instead, it is pain that lasts beyond an expected healing time or >6 months. Chronic pain can sometimes develop after an injury, but other times appears out of nowhere (like in the case of irritable bowel syndrome, fibromyalgia, chronic migraine). One obvious question on pain researchers' minds is: why?
The Biopsychosocial Model of Chronic Pain
To date, there is no conclusive answer to this question. However, chronic pain has become universally acknowledged as a "biopsychosocial" experience. The diagram above shows a model proposed by Gatchel and colleagues (read the original paper here) that details the biological, psychological, and social components that interact to produce the experience of chronic pain.
There are several biological factors that likely contribute to the development and persistence of chronic pain. Genetics can make someone vulnerable to expressing certain chronic pain-related traits. Peripheral processes include function of the endocrine (think hormones), immune (think inflammation), and autonomic (think the changes in body sensations during something stressful) systems. Central processes include function and structure of the spinal cord and brain.
Psychosocial factors have been historically overlooked in pain diagnosis and treatment. The biopsychosocial model has emphasized that psychosocial factors are just as critical of a focus as biological aspects of pain. It describes that the way a person responds to and thinks about pain, as well as the role pain plays in their daily lives, can impact the chronic pain experience. In turn, chronic pain can influence a person’s emotional and daily function. .
Psychological factors associated with the development of chronic pain and suboptimal treatment response include pain catastrophizing, depressed mood, and certain personality factors. Social factors are things like cultural norms and social expectations. But many other psychosocial components can also impact chronic pain; some of the review papers listed below provide a comprehensive assessment.
The key aspect of this model is that chronic pain isn’t just a biological phenomenon; all of these factors interact & are important to consider in understanding why a person has chronic pain and finding the best ways to treat it.
How does this model relate to chronic pain treatment?
In the past, chronic pain was primarily seen as a symptom that should be treated from a medical perspective (i.e., bio). If the pain did not respond to treatments, then the patient was sent home without other potential options. The biopsychosocial model helped change the way health providers approached chronic pain treatment - by viewing pain in the context of the whole person.
It is common now for chronic pain treatment teams to include specialists that represent biopsychosocial components. These kinds of teams are called "interdisciplinary" care teams, meaning medical physicians targeting biological aspects of chronic pain work with psychologists and/or social workers who focus on psychosocial aspects. Most of us are not born knowing how to deal with chronic pain and live a rich and happy life. Psychosocial treatments compliment medical care by teaching people how to best cope with chronic pain and connect them with community resources that can help achieve an optimal quality of life, even if the pain persists.
 Gatchel, R. J., Peng, Y. B., Peters, M. L., Fuchs, P. N., & Turk, D. C. (2007). The biopsychosocial approach to chronic pain: scientific advances and future directions. Psychological bulletin, 133(4), 581.
 Denk, F., McMahon, S. B., & Tracey, I. (2014). Pain vulnerability: a neurobiological perspective. Nature neuroscience, 17(2), 192.
 Bartley, E. J., & Fillingim, R. B. (2013). Sex differences in pain: a brief review of clinical and experimental findings. British journal of anaesthesia, 111(1), 52-58.
 Grace, P.M., Hutchinson, M.R., Maier, S.F., Watkins, L.R., 2014. Pathological pain and the neuroimmune interface. Nat. Rev. Immunol. 14, 217.
 Henry, D. E., Chiodo, A. E., & Yang, W. (2011). Central nervous system reorganization in a variety of chronic pain states: a review. PM&R, 3(12), 1116-1125.
 Adams, L. M., & Turk, D. C. (2018). Central sensitization and the biopsychosocial approach to understanding pain. Journal of Applied Biobehavioral Research, 23(2), e12125.
 Quartana, P. J., Campbell, C. M., & Edwards, R. R. (2009). Pain catastrophizing: a critical review. Expert review of neurotherapeutics, 9(5), 745-758.
 Boissoneault, J., Mundt, J., Robinson, M., & George, S. Z. (2017). Predicting low back pain outcomes: suggestions for future directions. journal of orthopaedic & sports physical therapy, 47(9), 588-592.
 Swimmer, G. I., Robinson, M. E., & Geisser, M. E. (1992). Relationship of MMPI cluster type, pain coping strategy, and treatment outcome. The Clinical journal of pain, 8(2), 131-137.
 Darnall, B. D., Carr, D. B., & Schatman, M. E. (2016). Pain psychology and the biopsychosocial model of pain treatment: ethical imperatives and social responsibility. Pain Medicine, 18(8), 1413-1415.
 NIH Interagency Pain Research Coordinating Committee. National Pain Strategy. Available at: http://iprcc.nih.gov/National_Pain_Strategy/NPS_Main.htm