Chronic pain is considered by the World Health Organization as a disease in itself.
We call chronic pain that appears every day or the vast majority of days in the last 6 months, or that which persists at least 3 months after the normal duration of the causal process.
It is usually linked in its origin to a tissue, bone, vascular or visceral lesion, which induces modifications of the nociceptive nervous system both at the peripheral and central level, and which lead to a greater sensitivity to noxious stimuli (hyperalgesia) and an increase in the duration of pain responses to them.
Chronic pain is therefore not, in many cases, proportional to the damage caused by it.
Small lesions such as those caused by shingles or a small surgical incision can lead to great pain. Sometimes spontaneous pain appears, that is, in the absence of a manifest stimulus. In these cases, the pain usually has a neuropathic component, a consequence of the nerve damage produced by the initial noxious stimulus.
Despite all the therapeutic alternatives currently available, 30% of patients with chronic pain do not find effective relief.
In the experience of chronic pain, in addition to the injury to the nervous system, another series of factors influence such as previous experiences of pain, the personality of the subject, or his emotional state. The combination of biological, psychological, and social factors determine that the pain experienced by human beings is difficult to reproduce in all its complexity in other animals.
In addition, the participation of multiple neurotransmitters, receptors, and ion channels in very different nerve structures, makes it necessary to use integrative approaches (pharmacological and non-pharmacological) to try to alleviate this type of pain.
According to data from 2009 on the prevalence of pain in Primary Care in Spain, one in three patients suffered pain and of them, half were diagnosed with chronic pain.
The most common symptoms of chronic pain are migraine, trigeminal and postherpetic neuralgia, diabetic neuropathy, low back pain, carpal tunnel syndrome, and chronic osteoarticular pain.
There are other medical conditions, such as multiple sclerosis or cerebrovascular accidents that, obviously affecting the motor system (progressive lack of mobility, or immobility of certain areas of the body), can also cause alterations in the sensitive nervous system that frequently cause pain chronic.