No one knows what causes fibromyalgia, although there are a number of theories. Some studies show that an injury or trauma, physical or emotional, may affect the central nervous system’s response to pain. For example, a 2002 Scottish study of 136 patients with a diagnosis of fibromyalgia and 152 controls found that 39 percent of those with fibromyalgia had significant physical trauma in the six months before they were diagnosed compared to only 24 percent of the controls. 

Some scientists theorize that trauma leads to biochemical changes in the muscles and, later, the central nervous system, leading to chronic pain, or that injury to the central nervous system interferes with brain wave patterns. Other researchers believe hormonal changes or infections, such as a flu virus, may trigger fibromyalgia.

Other studies have suggested that people with fibromyalgia have abnormal levels of several different chemicals in their blood or cerebrospinal fluid that help transmit and amplify pain signals to and from the brain. There also is evidence that the central nervous system’s ability to inhibit pain is impaired in these people. 

In addition to patient reports, brain-imaging studies have confirmed that when fibromyalgia patients are given a small amount of pressure or heat, they experience much higher amounts of pain, as if the “volume control” is set too high on pain processing. Whether these abnormalities are a cause or a result of fibromyalgia is unknown.

There are some scientists who suspect that lack of exercise and changes in muscle metabolism may play a role in fibromyalgia or that the opposite, muscle overuse, may be the key.

Sleep disturbance, a symptom of fibromyalgia, may also be a cause. Sleep disturbance lowers the production of a growth hormone crucial to the repair of muscles.

An established link exists between fibromyalgia and depression, but no one knows if depression is a cause or effect of fibromyalgia. What does seem to be true is that all of these conditions may contribute to fibromyalgia for different reasons.

Research is continuing to examine these and other potential causes in hope that a better understanding of what causes fibromyalgia could lead to ways to prevent it or to treat it more effectively.