The emotional factors which cause disease are joy, anger, brooding, sadness, and fear or fright. Under normal circumstances, these emotions are the appropriate reflection internally of stimuli from the outside world. Crying, laughing, and being happy are feelings normal to the human body. When they are not out of control, they do not adversely affect the zang fu and no disease ensues. But, when they are out of control, excessive anger can injure the liver, excessive joy can injure the heart, excessive brooding can injure the spleen, excessive sadness can injure the lungs, and excessive fright can injure the kidneys.
Anger arouses the ascent of qi.
Joy induces sluggishness of the qi. Excessive sorrow dissipates the qi. Fear causes the descent of the qi. Fright causes disturbance of the qi. And worry causes stagnation of qi.