A condition that causes extreme fatigue over a prolonged period, often for several years. It is most common in women aged between 25 and 45.
The cause is unclear. In some cases, the condition develops after a viral infection or after a stressful event such as bereavement. In other cases, there is no such preceding illness or event.
The main symptom of chronic fatigue syndrome is persistent tiredness. Other symptoms vary, but commonly include impairment of short-term memory or concentration, sore throat, tender lymph nodes, muscle and joint pain, muscle fatigue, unrefreshing sleep, and headaches. The disorder is often associated with depression or anxiety.
There is no diagnostic test for chronic fatigue syndrome, and investigations of the condition are usually aimed at excluding other possible causes of the symptoms, such as anaemia. A physical examination, blood tests, and a psychological assessment may be carried out. If no cause can be found, a diagnosis of chronic fatigue syndrome can be made from the symptoms.
Analgesic drugs (painkillers) or antidepressant drugs may help to relieve the symptoms. Physiotherapy or psychotherapy may also be helpful. Chronic fatigue syndrome is a long-term disorder, but the symptoms clear up after several years in some people.