Chronic Pain

The classical model of pain, first articulated by the philosopher Descartes in the 17th century, regarded pain as a sensory experience triggered by tissue damage. Despite the fact that this model is unsupported by empirical research, it continues to be a common misconception. Research on pain has demonstrated that it is a complex biopsychosocial phenomenon, with sensory, affective, cognitive, and social components. The International Association for the Study of Pain defines pain as being both a sensory and emotional experience. It goes on to state that pain is always a subjective experience, and its presence cannot be verified by any kind of objective test. Consequently, the only way of knowing if an individual has pain is through the verbal report or other communication of that individual. Chronic [Page 84]pain can sometimes persist in the absence of any identifiable physical cause.

In the acute phase following the onset of disease or injury, pain is often more closely associated with nociception. Nociception is a sensory system that alerts the brain to actual or potential tissue damage and initiates self-protective behaviors. Nociception, however, cannot be equated with pain, as nociception can occur without pain, and pain can occur without nociception. In contrast, as pain becomes chronic, its cognitive, affective, and social components tend to play a progressively larger role. Research studies using functional magnetic resonance imaging (f-MRI) have shown that the brain activity observed while experiencing physical pain is similar to brain activity observed while experiencing social pain or “hurt feelings.” This blurs the distinction between physical and social pain. Similar f-MRI studies have also found that physical pain and imagined pain also produce similar brain activity.

The complex nature of pain has led some to classify pain as being either “real” or “not real,” but this is a false dichotomy. Consider the example of someone whose foot is traumatically amputated in an accident. Many who experience this type of injury will experience “phantom pain,” or pain in the missing foot. Where is this pain? Is this pain “real” and “in the foot”? Or is this pain “not real” and “in the head”? Pain is an inherently subjective experience, and subjectively, this pain is clearly in the foot. Objectively though, there is no foot there to hurt. Consequently, it could be argued that the pain is actually in the stump, where the severed, damaged nerve ending is transmitting the wrong signal to the brain. However, the patient could counter that the pain cannot be in the stump, because the stump itself does not hurt. It could also be argued that the pain is in the brain, because the brain is involved in all subjective experience. The fact that all three of these explanations are correct in their own way illustrates the complex nature of pain. Because all pain is a subjective experience, the individual's report of pain should be accepted. At the same time, knowing that chronic pain is a complex and multidimensional phenomenon, the various factors influencing pain need to be explored.