Is Chronic Pain a Disease?


Some patients who experience persistent chronic pain seem to have no other underlying cause to their pain and it seems to bear all of the hallmarks of a disease. However, many pain specialists remain sceptical about the classification of pain as a disease, but they are in agreement that its treatment is oft neglected.

Pain has always been historically viewed as a symptom of disease. Thus the central tenet of pain management has been based on treating the disease so that the pain resolves.

Classification of pain as a symptom has been based on its subjective description. Pain is usually described in subjective terms, and thus it has many of the attributes of a symptom. There is no objective measure and pain scales are subjective.

Pain is a personal experience and assessment is through asking the patient to rank their pain intensity on a visual analog scale; there is no objective medical test of pain.

As a symptom, pain has been viewed as a warning system through the nerves about damage in some part of the body.

Something is compressing the nerve or causing irritation and so we sense pain. If pain is caused by forces outside the body, external trauma or injury to the body, then how can it be classified as a disease? But what about chronic neuropathic pain?

There are instances when pain persists to occur after the disease has been cured. In these cases of persistent pain there can be changes in the physiology of the body. These can become permanent and irreversible changes, which then trigger chronic pain. Pain has become more than just a symptom and takes on some of the traits of disease.

What does it matter how pain is categorised and whether it be a disease or symptom? Surely the goal is just to remove the pain and it doesn’t really matter whether it is classified as symptom or cause?

Well it does matter to how it is managed in many cases. If pain is classified as a disease or more than just a symptom even, the treatment approach needs to be different. The pain becomes more the central focus of the treatment strategy. There is a general consensus among experts that for persistent pain to be a disease in its own right it needs to fulfil certain criteria:

  • There needs to be signs, symptoms and pathology.
  • Pain pathology must persist beyond resolution of what is considered to be the initial disease state.

Increasingly, persistent pain is being described as no longer being a function of a normal healthy nervous system. In certain cases, nerve injury triggered by a variety of causes may lead to spontaneous firing and a cycle of pain response in the periphery of the body. Also in the central nervous system in the spinal cord there way be an increased pain response when the pain in the peripheral nervous system increases or there is some disease of the nervous system.

Some people may have a genetic susceptibility to developing persistent pain. And pain can occur in the periphery in those patients who have a pathology that is independent of any primary disease.

This kind of thinking has changed the ideas about management of chronic pain in order to attain a cure to pain pathology.

Traditionally, chronic pain is treated with analgesics, systemic and non-systemic opioids, which do not improve function.

Using new imaging technology it has been possible to visualize permanent changes in the brain associated with chronic pain. With chronic pain, a whole cascade of hormones can be released, such as cortisol, which ultimately cause damage to the immune system and the kidneys.

Also if pain is adequately treated it is found that people recover more quickly from surgery and in some cancers it improves outcome. So treating the pain can improve prognosis and it is worth doing early. Treating acute pain early will prevent the brain changes that lead to chronic pain.

Defining pain as a disease however is not straightforward. As there are people who have chronic disability with little pain and others who have no disability with chronic pain.

In this scenario treating the pain or the disability is the question. Abolishing the pain may minimize changes in the central or peripheral nervous system that will contribute to chronic pain. Other issues, such as psychosocial factors and how the patient views their pain in a more holistic context may also be important.

So whether chronic pain should be classified as a self-perpetuating disease remains contentious. The issues around that management of that pain should be viewed in a holistic context. Treating pain aggressively and early may remove the risk of the development of persistent pain, but a more holistic treatment approach to restore function is the ideal.

Conor Caffrey is a science and medical writer.

 

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