What Is Chronic Pain?
Chronic pain is pain that lasts much longer than would be expected from the original problem or injury. When pain becomes chronic, your body may react in several ways. Chronic pain may be characterized by abnormalities in brain hormone, low energy, mood disorders, muscle pain, and impaired mental and physical performance. Chronic pain worsens as neurochemical changes in your body increase your sensitivity to pain. Then you begin to have pain in other parts of your body that do not normally hurt.

What Happens With Chronic Pain and Depression?
If you have chronic pain and depression, you've got plenty of company. Depression is one of the most common psychological issues facing people who suffer from chronic pain, and it often complicates the patient's conditions and treatment.

Consider these statistics:
According to the American Pain Foundation, about 32 million people in the U.S. report have had pain lasting longer than one year. From one-quarter to more than half of the population that complains of pain to their doctors are depressed.
On average, 65% of depressed people also complain of pain.
People whose pain limits their independence are especially likely to get depressed.