The cause of fibromyalgia is unknown.
Studies suggest that an injury, trauma or infection may affect the central nervous system’s response to pain. Some researchers believe that trauma leads to biochemical changes in the muscles, and later, the central nervous system, leading to chronic pain. Others believe that an injury to the central nervous system interferes with brain wave patterns related to pain. Still others believe hormonal changes or infections, such as a flu virus, may trigger fibromyalgia.
Some studies have suggested that people with fibromyalgia have abnormal levels of different chemicals in their blood or the fluid in the brain and spine that help transmit and intensify 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.