The cause of this disorder is unknown. Pilot studies have shown a possible inherited tendency toward the disease.

The cause of fibromyalgia and chronic fatigue syndrome remains elusive, but there are many triggering events thought to precipitate its onset. A few examples would be an infection (viral or bacterial), an accident or the development of another disorder, such as rheumatoid arthritis, lupus, or hypothyroidism.

These triggering events probably don‘t cause FMS but rather they may awaken an underlying physiological abnormality that is already present in the form of genetic predisposition.

The disorder has an increased frequency among women 20 to 50 years old. It is estimated that women are 70 to 90% of the patients.

Fibromyalgia is not caused by depression.