Some researchers believe that fibromyalgia is due to changes in the way that the brain processes pain signals. Some believe that it is due to changes in the fascia, the thin layer that surrounds all muscles and organs in the body. While others believe that fibromyalgia symptoms are caused by metabolic changes in the muscles due to long term stress or overuse.
According to the American College of Rheumatology, fibromyalgia is the second most common rheumatic disorder in the United States behind arthritis. While some organizations put the number of Americans suffering from fibromyalgia at three million, other sources believe the number is much higher – perhaps eight or nine million.
Symptoms can begin after physical trauma such as surgery, injury, or infection, or after psychological or emotional stress.
Fibromyalgia symptoms can come on gradually over time or begin all at once.