The Evolutionary Significance of Chronic Pain: Survival of the Whiniest?

Acute pain signals tissue injury. The hand of an unfortunate victim accidentally comes in contact with that hot iron; he pulls the hand away in response to pain, lest the burn become deeper and cause more extensive tissue injury. In a few days all is healed, and our erstwhile casualty is ready to resume life, prepared to do battle with the next acute injury.

So, wherefore chronic pain? What purpose does it serve? Animals generally do not display evidence of chronic suffering due to pain; they dare not show any behavior which may be construed as weakness, as this might invite attack. In contrast, there is a school of thought hypothesizing that humans appear to have learned that talking about chronic pain may garner attention, which in turn may give emotional emollients---and even economic rewards.

But this theory does not explain the stoic ones who quietly tolerate chronic pain, many of whom forego treatments with the potential to positively and remarkably alter their lives.

Chronic pain is difficult to manage, often being refractory to pharmacologic intervention, including opioids. For many researchers, the key to relieving chronic pain is in the disruption of the pain transmission sites at 1) the periphery, where the pain may result from injury or illness such as arthritis, 2) in the spinal cord, which acts as a gate to transmission of the sensation of pain to higher levels of the nervous system, and 3) the brain (that highest of the higher levels of the nervous system).

Chronic pain involves central sensitization, which occurs at each of the aforementioned transmission sites. This sensitization renders chronic pain so difficult to manage, as the same input will have a lower threshold to firing and a magnified sensitivity to light touch, heat and other noxious stimuli.

A variety of cells serve to support and protect the cells of the brain tissue, including microglia, oligodendrocytes and Schwann cells; all of these glial cells play a role in chronic pain. These cells are mobilized after peripheral injury, secreting a variety of nerve growth factors and substances that can sensitize the nerve cells of the brain. Molecules increase in the central nervous system in response to nerve injury, producing behavioral hypersensitivity and an increase in a variety of biochemicals that can cause inflammation.

Unfortunately, efforts to target these rogue cells to alleviate chronic pain have not been successful.

At least some of the science is explaining why we suffer chronic pain. I am waiting for the science that will explain the science of chronic pain.

Chronic pain invariably leads to some degree of emotional pain (for example, depression) in most sufferers. Many in the field of evolutionary psychology have long described manifestations of depression as attempts at signaling unhappiness to close friends and family members: This becomes an elicitation of support from society. The evolutionary psychologists conclude that heretofore "pathologic" behaviors become bargaining tactics to manipulate others into providing the support that might otherwise not be forthcoming.

I believe, however, that evolutionary psychology is at its best when commenting on the daily ramifications of typical human behavior, not the individual variations of suffering. The manner in which human beings deal with pain depends on personality type and the cultural milieu. Philosophers and therapists must not ignore these realities as they consider the individual with chronic pain.