Why is the time of day important in determining pathologies of Yang or Yin deficiency?
Answer:
In the natural order of bodily functioning, yang activities should take over during the day, dawn through afternoon, and yin activities should predominate during the evening and nighttime. This is why we wake up and become active in the morning and naturally become quiet and calm in the evening. Two common conditions illustrate what happens when yang or yin are deficient. If a person is deficient in yang energy, when morning comes, their own yang cannot perform its warming function, and diarrhea may result. This is what’s known as daybreak, or cock’s crow, diarrhea. Why would this person not have diarrhea at night? Because night time is not when we expect yang to be at its zenith, but morning is when we do. For yin deficient patients, as afternoon and evening approach, the natural cooling and calming cannot take place. These people will have afternoon and evening heat, fevers or sweats, and insomnia, nervousness and restlessness. The yin energy cannot overcome the yang influence on the body, so the heat rises, unchecked.
This is why going to sleep at a normal hour is so important for health. When our Yueying Li helped me counsel a patient suffering from insomnia, she asked him what time he went to bed, and he said “1:00 am." She said, “That is the next day!” If people turn night into day, it is no wonder that their yin and yang will become disordered.