The cause of fibromyalgia is unknown. However, people with fibromyalgia have abnormal levels of a chemical messenger called Substance P in their cerebrospinal fluid. Substance P is a neurotransmitter that is involved in sending pain signals to the brain and it is possible that people with fibromyalgia are more sensitive to pain because their levels of this neurotransmitter are higher. It is as if their threshold for pain has been turned down so low that even a slight touch or movement within a joint is perceived as painful. The cause or causes of this abnormality in Substance P levels remains unknown.

There are several theories as to what leads to this heightened sensitivity to pain and it may be due to a combination of factors. One theory is that repeated nerve stimulation causes the brains of people with fibromyalgia to become more sensitive to pain. Once the brain circuitry is altered, the brain develops a “memory” for pain sensation, causing any touch stimulation to be perceived as painful. But what initiates this process of so-called “central sensitization” has not been explained.

Some of the factors that may be associated with developing fibromyalgia include:

• Genetics:  Fibromyalgia tends to run in families. Genes may regulate the way people react to stimuli. Specifically, certain genes may cause people to react strongly to stimuli that other people would not perceive as painful.
• Stress: Many people believe fibromyalgia may be triggered by physical or emotional stresses such as a car accident or the death of a loved one.
• Injuries: Injuries that are caused by repeating the same motion over and over or trauma to the upper spinal region may be triggers for fibromyalgia.
• Infection: Some researchers believe that a viral or bacterial infection may trigger fibromyalgia.
• Nervous system abnormalities: Problems with the body’s “alert system,” the sympathetic division of the autonomic nervous system, may lead to fibromyalgia.