American College of Rheumatology. In some cases, the symptoms of this disease may be debilitating. The cause of fibromyalgia is unknown, but it is believed to involve disturbances in the way the central nervous system sends and receives messages, as reported by Whaxy. This chronic health problem, which affects an estimated 5 to 12 million Americans, has no cure but medications and self-care can reduce symptoms for some patients. For the entire article, click here. To learn more about other conditions that can be treated with medical marijuana, click here.