Last updated: Tue, Aug 13, 2024
Melzack and Wall1 have suggested that many forms of chronic pain might be understandable in terms of the nervous system's homeostasic mechanisms. We've seen (How Pain Is Made) that our nervous system relies on constant tuning and retuning of neuronal sensitivities. If the setpoints of our systems change, perhaps due to unusually forceful or unusually long-lasting patterns of stimulation, the mechanisms that keep the system from creeping out of tune in a normal individual may force the system to continue to operate in a range that's hard to bear:
Some pains are best understood as a failure of control. When pain exists and a drug, a surgical lesion, physiotherapy or psychotherapy are initiated, the remaining control mechanisms will react in an attempt to re-establish the pain. This reaction may provide an explanation common to all eventual failures of therapy. A placebo which initially produces an excellent response fails on repeated administration. Many physiotherapies may do the same. An initially satisfactory dose of morphine may not be effective on the third application; but if the dose is raised, the effect may be strong enough to overwhelm the counter-reaction of the control mechanisms. The failure of surgery such as cordotomy [cutting the spinal cord] to control pain after some months of success may also be seen as due to a slow readjustment of control, in which there is enhanced use of previously minor pathways so that they can produce major effects.