Acute pain is caused by an injury or health problem that leads to tissue damage. The pain has a clear source and pain signals travel from the injury along the nerves. Gates in the nerve pathways open to allow these signals through to the brain. While you heal, the brain’s normal pain control system lessens the pain through the release of endorphins. These natural chemicals reduce pain by closing the pain gates. Once the injury or health problem heals, the pain goes away.

When pain lasts over a long period of time it is called chronic. This includes pain that you regularly feel, even if it comes and goes. Chronic pain may be due to chronic stimulus from an ongoing injury or health problem. Arthritis, back injury, nervous system damage, and headaches are common causes of chronic stimulus. Chronic pain is not always a signal of harm to your body. Problems with the pain control system may lead to a chronic pain syndrome. Chronic pain syndrome involves the persistence of pain when no cause can be found. This may occur because the brain can not produce enough endorphins to shut the pain gates. Sometimes pain signals continue after an injury has healed.