The Nature of Chronic Pain

Chronic pain has been defined as pain or discomfort that has persisted continuously or intermittently for longer than three months. By this reckoning chronic pain is very common. Some studies have found that one third of people between the ages of 25 to 35 described themselves as suffering from chronic pain. This rises to fifty percent of respondents in those older than 60.

Pain that doesn’t go away can have serious and insidious effects. The long-term consequences of the disability and depression caused often affects family and friends.

Reasons for Chronic Pain

Pain is normally a response to injury to the body’s tissues. Sometimes the reason pain continues is simply that the damage hasn’t been or can’t be repaired. Inflammation is a cause of pain and sometimes it persists if, for example, a wound will not heal because of a stubborn infection.

In other cases however the initial cause of the pain has gone or the damage seems insufficient to cause the degree of pain it’s producing.

Mechanisms of Chronic Pain.

The reasons for the development of chronic pain are not completely understood but as you would expect there are a number of ideas.

• Continuous sensitisation of pain receptors: these receptors send pain signals along the nerves to the brain. However there is also traffic going the other way. Signals coming to the pain receptors down the nerve cause the production of chemicals which stimulate fluid accumulation and swelling in the area of the tissue damage. This is to help the healing process. But sometimes the system goes wrong and the swelling persists for longer than normal. Pressure then builds up on the surrounding tissue which limits blood supply to the area and this in turn will cause more pain signals to be generated. In this way a vicious cycle is produced.
• Increase in nerve traffic: pain will cause the number of pain receptors in the area affected to increase. This in turn will increase pain signal traffic to the brain. This change occasionally persists after the injury has healed so the even minor stimulation of the receptors will be interpreted as pain.
• Disturbance to anti-pain system: some pathways from the brain and going down the spine have an anti-pain function – they seem to dampen down the pain signals. It’s common in many systems of the body for a balancing and control mechanism to exist and pain is no exception. It’s suggested that something goes wrong with this process so that pain is not dampened down as it should be. The pain signal then gets to the brain at maximum strength.
• Psychological factors: signals coming from pain receptors are interpreted by the brain as pain – we don’t feel pain until this interpretation takes place. This requires processing through a number of areas of the brain such as memory centres and emotion areas. It’s possible that individual areas like these vary from person to person or from time to time. Such variation means that the same intensity of pain signals could be interpreted differently and therefore cause variation in the degree to which pain is felt. In these circumstances quite minor signals from the pain receptors would be magnified by these areas of the brain so the pain experienced would be quite considerable.

Resource

Muscle Pain by Mense and Simons. Pub. Lippincott Williams and Wilkins 2001.

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