The causes of coughing at midnight in winter can be divided into two main categories: 1. cold causes: winter is a cold season, and cold seasons tend to hurt the lungs; midnight is the time when yin is in full bloom, and cold when yin is in full bloom also has a great impact on the lungs, called cold evil hurting the lungs; 2. heat causes: winter is the time when everything is hidden, and what is hidden is yang energy, that is, the fruit that comes out of the summer when yang energy is in full bloom, which has to be collected in winter, and the lower part of the collection The amount of yin is not enough to contain the yang that is latent, so yin does not contain yang, and yang will crash, and yang is hot in nature, and heat has a restraining effect on the lungs in the relationship of the five elements.