CFS Definition

In order to receive a diagnosis of chronic fatigue syndrome, a patient must satisfy two criteria:

1) Have severe chronic fatigue of six months or longer duration with other known medical conditions excluded by clinical diagnosis; and

2) concurrently have four or more of the following symptoms: substantial impairment in short-term memory or concentration; sore throat; tender lymph nodes; muscle pain; multi-joint pain without swelling or redness; headaches of a new type, pattern or severity; unrefreshing sleep; and post-exertional malaise lasting more than 24 hours. The symptoms must have persisted or recurred during six or more consecutive months of illness and must not have predated the fatigue.

Centers for Disease Control and Prevention