Nociceptive, Neuropathic, and Psychogenic Pain

Pain may be caused by an injury that stimulates pain receptors. Pain receptors, located on the tips of nerve cells, recognize and react to pressure, extreme temperatures (hot or cold), or substances released by other cells. This type of pain, called nociceptive pain, may be accompanied by inflammation. Infections, burns, cuts, a severe lack of oxygen in the blood, and stretching of or pressure within an organ can injure tissues and cause nociceptive pain.

Abnormal nerve activity can cause another type of pain, called neuropathic pain. Shingles and diabetes mellitus are examples of disorders that can produce abnormal nerve activity (with shingles, the pain is called postherpetic neuralgia). Sometimes, after a nerve is injured, abnormal nerve activity causes pain to persist long past the time expected for healing of the injury.

Occasionally, pain is attributed—at least in part—to a psychologic disorder, such as depression. Pain attributed to a psychologic cause when no physical cause can be found is called psychogenic pain.

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