是一种免疫性疾病，主要的原因是此类病患缺乏对某种毒（尤其是EB病毒）感染的抵抗力。此外，长期处於压力以及某些荷尔蒙分泌失常亦是导致慢性疲劳症候群的主要原因之一。
慢性疲劳症候群：不明原因的突然虚弱疲劳。
Chronic fatigue syndrome (CFS) : Sudden debilitating fatigue of unknown cause.
慢性疲劳症候群可能是一个更准确的名字，能引起对该疾病与干扰的免疫系统有关的事实的关注。
Chronic fatigue immune dysfunction syndrome would be a more accurate name that would call attention to the fact that the disease is tied to a disturbed immune system.
研究显示，相较于健康的女性来说，有慢性疲劳症候群的女性在早上的皮质醇含量比较低。
The study shows that women with chronic fatigue syndrome had lower cortisol levels in the morning, compared with healthy women.
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