No single cause for chronic fatigue syndrome (CFS) has been identified. Suggested causes include chronic viral infections, food allergy, adrenal gland dysfunction, and many others. The current definition is disabling fatigue lasting more than six months that reduces activity by more than half. There may be difficulty sleeping, swollen lymph nodes, and/or mild fever. When there is muscle soreness, fibromyalgia may be the actual problem.
In addition to fatigue, there may also be muscle pain, joint pain not associated with redness or swelling, short-term memory loss, and an inability to concentrate. Some people with chronic fatigue syndrome also experience difficulty sleeping, swollen lymph nodes, and/or mild fever.
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