Chronic Pain

Chronic pain is persistent long-term pain.

Pain is a localized, unpleasant sensation that can range from a feeling of mild discomfort to an excruciating experience. Pain serves the function of alerting the body to possible causes of injury, or making an affected person (or animal) withdraw from a source of harm. It may be acute (in which it appears and disappears suddenly) or chronic (in which it persists for days, weeks, or even longer).

Mechanism of pain 

Pain results from the stimulation of sensory nerve endings called nociceptors in the skin. Pain receptors are also present in other structures, such as the blood vessels and tendons. Some nociceptors respond only to severe stimulation, such as cutting, pricking, or extreme heat; others respond to warning stimuli such as firm pressure or stretching. Signals that arise from the nociceptors are transmitted via nerves to the brain. In addition, chemicals called prostaglandins trigger inflammation and swelling, and further stimulate the nerve endings. Pain that may be felt at a point some distance from the cause is known as referred pain (see pain, referred).

Psychological aspects of pain 

Pain is usually associated with distress and anxiety, and sometimes with fear. People vary tremendously in their pain thresholds (the level at which the pain is felt and the person feels compelled to act). The cause and circumstances of the pain may also affect the way it is perceived by the sufferer. The pain of cancer, because of fear of the disease, may seem much greater and cause more suffering than similar pain that results from persistent indigestion. Unexplained pain is often worse because of the anxiety it can cause; once a diagnosis is made and reassurance given, the pain may be perceived as less severe.

In some cases, pain may be felt due to emotional reasons rather than any obvious physical cause (psychogenic pain). The experience of pain may be reduced or blocked by arousal or strong emotion; for example, an injury sustained during competitive sport or on the battlefield may go unnoticed in the heat of the moment.

Some people believe that mental preparation for pain, in advance of situations such as childbirth or in experiments to test pain, can greatly reduce the response. A person’s response to pain is also greatly modified by past experience; the outcome of previous episodes of pain may affect the way in which the individual copes with subsequent pain.

Factors such as insomnia, anxiety, and depression, which often accompany incapacitating chronic illness, lower tolerance to pain. Many hospitals now have specialist pain clinics, in which people with severe pain that has proved difficult to control may be assessed and treated. Such patients include those with advanced cancer and poorly understood conditions such as facial pain and various types of neuralgia.


Treatment is for the underlying cause of the pain. It may involve analgesic drugs, electrical stimulation (TENS), surgery, or therapies such as acupuncture.