Chronic fatigue syndrome (CFS) is a complicated disorder in which sufferers experience extreme fatigue that worsens with physical or mental activity, but is not resolved with rest. There are varying theories as to the cause of CFS, from viral infection to psychological distress, but ultimately the cause is unknown.
In addition to extreme fatigue, CFS is also characterized by loss of memory or concentration, sore throat, painful and enlarged lymph nodes, muscle and joint pain, and headaches of varying severity.
Patients can often be effectively treated for CFS, and may recover in a few months time. Common treatments include moderation of activity, steady exercise, cognitive behavior therapy, and treatment for underlying conditions including depression, muscle pain, or sleep problems. There is also some research into experimental therapies and the use of various medications.