Chronic fatigue syndrome and fibromyalgia (CFS and FM, respectively) are both illnesses that have been given a name based on a presentation of signs and symptoms.
They are both very similar, and have historically generated controversy on how to diagnose them, what causes them and how to treat. Both are characterized by persistent pain and fatigue, and many people who experience these syndromes can also have difficulty sleeping, trouble thinking, depression, headaches, digestive issues and swollen lymph nodes.
More than 1 million Americans have chronic fatigue and about 5 million have fibromyalgia, as estimated by the CDC. Both occur more often in women and adults.