What may happen is an infection, a very stressful life event, or an accumulation of persistent stress causes worry and disturbs sleep at night. This leads to irregular times of getting up and going to bed, and more rests taken during the day. Thus, the usual daily routine and normal sleep–waking cycle, both needed to reset the biological clock, are disrupted. The biological clock then loses control over body rhythms, resulting in the mental and physical symptoms of CFS.
