- The patient must have severe chronic fatigue of six months or longer duration with other known medical conditions excluded by clinical diagnosis.
- The patient must 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
- Post-exertional malaise (deep fatigue and exhaustion following physical exertion) 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.
Source: Chronic Fatigue Syndrome MayoClinic.com, 2005