About four out of five people with chronic fatigue syndrome are women, and the condition more often strikes people in their 20s and 30s. Diagnosis is made by excluding other disorders, such as infectious mononucleosis, that could account for the symptoms. Chronic fatigue syndrome can be disabling as well as lengthy, lasting months or even years, with symptoms varying in severity. Relapse is common, but many sufferers retain only minimal symptoms within five years, and other make a complete recovery.

The cause of chronic syndrome is unknown. Sometimes it follows a viral infection (with the flu virus or with the Epstein-Barr virus, which causes infectious mononucleosis); however, some experts think such infections are coincidental or the result of lowered immunity in the early stages of the syndrome. Recent research has found that people with the condition have higher than normal levels of melatonin, a hormone produced by the pineal gland and thought to influence daily body rhythms. Other suggested causes include pesticide or lead poisoning, and a low oestrogen level.

Psychological factors are often significant. One in two sufferers feels depressed, and one in four has some other mental health problem, but it is unclear whether this is a cause or an effect of the disorder. While studies have shown that the strongest risk factors for the condition are depression, anxiety, and stress, these are also an understandable result of the experience of having the illness, especially if it lasts for months or years. Mind and body are intimately linked by hormones, neurotransmitters and other body chemicals whose levels can be altered by both physical and mental illness.

Besides over whelming weariness, chronic fatigue syndrome can cause headaches, nausea, sleep problems and weak, aching or twitchy muscles. Symptoms experienced by sufferers can include poor concentration and memory, difficulty in keeping warm and swollen lymph nodes (glands). Other possible symptoms of chronic fatigue syndrome are dizziness, slurred speech, sore throat, fainting, breathlessness, and an abnormal sensitivity to sound, light, touches and smells.

Improve your lifestyle with a good diet and regular exercise. Try to reduce sources of stress in your life and learn and practice more effective stress management strategies, especially if you have already had one or more episodes of chronic fatigue syndrome.