Chronic fatigue occurs when symptoms of exhaustion or lack of energy last for more than six months. The specific cause of this long-lasting exhaustion is unknown. However, it is thought that sleep disturbances, hormone levels, and stress may play a role. In many cases, a person's lack of energy may be a symptom of another problem, such as fibromyalgia, cancer, or a reaction to medication.
Most people will experience fatigue at some point in their lives. In most cases, fatigue:
- Refers to exhaustion during or after usual daily activities
- Refers to a lack of energy to begin these activities
- May result from exertion, lack of sleep, or illnesses such as colds
- Generally goes away after getting more rest or recovering from a cold.
However, chronic fatigue occurs when symptoms of exhaustion or lack of energy last for more than six months.
Chronic fatigue is a symptom of many diseases. While chronic fatigue syndrome (CFS) is a condition, chronic fatigue is only one symptom. In order to be diagnosed with chronic fatigue syndrome, a person must have chronic fatigue and 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 (insomnia)
- Post-exercise fatigue lasting more than 24 hours.
(Click Chronic Fatigue Symptoms for a closer look at the symptoms of chronic fatigue.)