In the Chinese system of health, imbalance in any of seven emotions may be particularly associated with disharmony in the body. However it is only when an emotion is either excessive or insufficient over a long period, or when it is suddenly and powerfully experienced, that it may generate imbalance and illness. A classic text explains that excessive joy is associated with slow and scattered qui; excessive anger induces the Qi to ascend; excessive grief and sadness weakens Qi; knottedness or stuckness is generated by excessive pensiveness; fear induces descending Qi; and fright induces chaotic Qi. The Heart and Liver are considered most susceptible to emotional disturbance.