Fibromyalgia is a frustrating condition. Not only can it be incredibly painful, but we, unfortunately, know relatively little about it. Doctors have yet to determine fibromyalgia's exact cause, which makes treating it a sizable challenge.

Women are also 10 times more likely to suffer from fibromyalgia than men. A fact that, unsurprisingly, has no known explanation.

There is evidence on what might cause fibromyalgia, but the results are varied. Findings include:

• The chronic pain associated with fibromyalgia may due to abnormalities in the endocrine system and autonomic nervous system. Some researchers believe that changes in the autonomic nervous system (which is activated when you are stressed) and endocrine system (which releases hormones in response to stress) causes the widespread chronic pain associated with fibromyalgia. An over-active autonomic nervous system induces excessive hormones that sensitize pain receptors, causing pain and tenderness.^1,2

• Fibromyalgia may be linked to physical or emotional trauma via post-traumatic stress disorder.²

• Genetics may play a role since fibromyalgia seems to run in families.³

• Bacterial or viral infections may cause the condition. Hepatitis C virus, HIV and Lyme disease have been associated with fibromyalgia and some evidence suggests vaccinations may also cause the disorder.³

• Muscle tissue abnormalities may be to blame. Muscle abnormalities can be structural, metabolic, or functional. Muscle abnormalities may be caused by disturbances in the endocrine system in that decreased growth hormone levels that may prevent muscle tissue from properly repairing.⁴

• Some research suggests that the musculoskeletal pain of fibromyalgia may be caused by central sensitization. Central sensitization occurs when the central nervous system becomes sensitized, which increases the amount of pain you feel.⁵

• It may be linked to abnormal blood flow. A November 2008 study determined that fibromyalgia may be connected to abnormal blood flow in two areas of the brain. The study found that women with fibromyalgia have too much blood flow in the area of the brain that interprets pain intensity. Conversely, they have too little blood flow in the area of the brain that is involved in pain response. The researchers also found that the more severe the symptoms, the more severe the abnormal blood flow.

Like many disorders, it's quite possible that fibromyalgia does not simply have one cause; rather, many factors may impact your likelihood of developing the condition. The research may yield separate conclusions, but it is giving the medical community a better understanding of fibromyalgia. In turn, it will help create effective treatments.