Yīn-yáng disharmony

Imbalance between any yīn and yáng elements of the body and evils within the body. Plain Questions (素问 sù wèn, yīn yáng yìng xiàng dà lùn) sums up the essence of yīn-yáng disharmony as follows, When yīn prevails, yáng ails; when yáng prevails, yīn ails. When yáng prevails, there is heat; when yīn prevails, there is cold. Yīn and yáng can fall out of harmony in more than one way. When the counterbalancing principle observed in ebb and flow breaks down, a surfeit of one pole means a deficit of the other. A fierce sun parches the land, and a long winter shortens the summer. Likewise, a deficit of one complement is often observed with a surfeit of the other, as a lack of warmth manifests as cold. Sometimes, when interdependence breaks down, a deficit of one complement can lead to a deficit of the other. For example, absence of rest can make incessant activity unproductive. Since both evils and aspects of the body may be classified according to yīn and yáng, both health and disease may be viewed in terms of yīn and yáng. When the yīn and yáng elements within the body and between the body and the environment are in balance, the body is healthy. When any aspect of the balance is upset, disease arises. When a person is healthy, the principle of interdependence and mutual counterbalancing of yīn and yáng operates. A morbid imbalance is seen in terms of a failure of these relationships, or in terms of the mutual convertibility of yīn and yáng.