About 100 million Americans live with chronic pain. For them, a condition like arthritis, fibromyalgia, nerve damage, migraine headaches, or cancer has caused unrelenting pain that persists day after day, month after month.

Migraine headaches are a common source of chronic pain, affecting 1 in 10 Americans, most of them women. These are not just everyday headaches. Migraine symptoms also include nausea, vomiting, light and sound sensitivity, auras, and other visual disturbances. Because doctors still don?t fully understand what causes migraines, they haven?t been able to develop a cure for this condition. Treatments aim to reduce the frequency of migraine attacks and relieve symptoms when they start.

Fibromyalgia is another poorly understood condition. The estimated 5 million Americans who have this condition experience fatigue and pain in particular spots around their body. Other fibromyalgia symptoms include sleep problems, headaches, sensitivity to heat and cold, bowel issues, and memory problems.

Back problems are another source of chronic pain. Sciatica affects the lower back and legs. It starts in the sciatic nerve, which runs down the lower back, hips, buttocks, and legs. A herniated disk that puts pressure on the sciatic nerve often triggers sciatica. Spinal stenosis?a narrowing of the spine?can also put pressure on the sciatic nerve. Sciatica can be very painful, but medicines, physical therapy, and other treatments usually improve the pain within a few weeks.

Sometimes back pain can be traced to the kidneys, which are located on the back side of the body. Many people mistake kidney pain for back muscle strains. The most common causes of kidney pain are infection, kidney stones, polycystic kidney disease (in which growths called cysts form in the kidneys), bleeding, and kidney cancer. Because kidney pain can signal a more serious condition, it?s important to call the doctor for any constant, dull pain on one side of the back.