Chronic Fatigue Syndrome (CFS) is also known as myalgic encephalomyelitis. CFS is present most often with patients in their 40s and 50s, and occurs more often in women. It is often a diagnosis of exclusion based on patient history and a sudden onset that is characterized with a flu-like illness or after several months of extreme stress. Symptoms are often unrelieved by rest, increase with exertion, and are present for at least six months.

Possible symptoms of Chronic Fatigue Syndrome may include: