Pain has a complex character and is best understood by considering biological, psychological and social factors. In this article we briefly consider the theories that have developed to help understand the process of pain.
Our interpretation of pain seems to vary over time and across cultures. Pain, it seems, is a very personal experience and does not always need to relate to physical or pathological factors. In a previous article (“The Nature of Pain”) it was pointed out that even when physical trauma occurs it may not equate with the sense of pain and in some cases may not even appear at all.
Because of its variable nature attempts to explain pain from a theoretical perspective have not always met with success. Descartes (1664) likened pain to the ringing of a bell at the end of a rope. As the rope is pulled, so at the almost the same instant, the bell rings (prick your finger, you feel the pain). The idea of specific pathways for pain was to remain for a further 300 years. Theories became more elaborate as ideas about pain ‘spots’ over the skin (von Frey, 1894) were superseded by ideas involving different types of pain fibre and pain receptors. Whilst the specificity model has illuminated information about neural pathways, its main weakness is the fact that it cannot explain how or why sensations of pain varies so much according to individuals and circumstances. In such a model we should all perceive pain the same.
As a result of Beecher’s research with wounded servicemen (1959) it appears that psychological aspects play a crucial role in how we perceive pain. Severely wounded men will often complain of very little pain. One idea is that the relief that follows removal from a combat zone acts as analgesia, but it is also possible that the bodies own natural opiods may also have such an effect.
One of the most influential alternatives to specificity theory is a model of pattern theory developed by Melzack and Wall (1965). The ‘Gate Control’ Theory as it is known, is also a prime example of the biopsychosocial model in that it attempts to encompasses biological, psychological and social aspects into our understanding of pain:
According to the model, a system exists within the spinal cord in which messages to and from the brain serve to open or close the ‘gate’. So, if I bang my knee, a neural message is passed to transmission cells in the spinal cord which in turn alert the brain to my discomfort. The physical injury has opened the gate via small & large diameter nerves. My psychological state also has an effect on opening the gate. If I’m anxious for example, or if I dwell on the injury, the longer the chance I will perceive discomfort. The gating system is a two way process however. Conditions that help to close the gate are counter-stimulation (rubbing it better), or taking an aspirin, or being distracted by something more important than the injury.
Does this mean we understand how pain works? Well, not quite. Even though the Gate Control Theory provides an elegant way in which to conceptualise the pain / analgesia process, there are one or two issues still to be addressed. The first is that, to date, no gating mechanism has actually been found. Secondly, the theory still assumes an organic basis for pain and although an attempt has been made to link mind and body it is still the case that physical states are seen to influence psychological states and vice versa. Therefore the theory provides a mind-body overlap, rather than a truly integrated model.