Sleep is in close relation with the circulation of weiqi and the conditions of yin and yang. Sleep is also, to a certain degree, in relation with the conditions of qi and blood as well as the functions of the heart and kidney. Inquiry of whether the sleep time is long or short, whether the sleep is easy or difficult and whether there is dream or not is helpful for understanding whether yin, yang, qi and blood are predominant or declined and whether the functions of the heart and kidney are strong or weak.

Insomnia
Insomnia is characterized by difficulty in sleeping, or easiness to wake up and difficulty in falling asleep again, or shallow sleep or easiness to be disturbed in sleep, or even inability to sleep all night, usually accompanied by frequent dreaming. The pathogenesis of insomnia is the failure of yang to enter into yin and failure of spirit to maintain calm. The causes of insomnia are various and the nature of insomnia is either asthenic or sthenic. Asthenic syndrome of insomnia is usually caused by depletion of blood or exuberance of fire due to yin asthenia and malnutrition of heart spirit; while sthenic syndrome of insomnia is caused by exuberance of phlegmatic heat inside, or retention of food and disturbance of the heart spirit.

If insomnia is accompanied by palpitation, dysphoria and reddish tongue with scanty fur, it is caused by insufficiency of heart yin; if difficulty in sleeping is accompanied by palpitation and aching flaccidity of the loins and knees, it is caused by imbalance between the heart and the kidney; if easiness to wake up is accompanied by palpitation, reduced appetite, pale tongue and weak pulse, it is caused by asthenia of both the heart and the spleen; if insomnia is accompanied by profuse sputum and yellowish greasy fur, it is caused by phlegmatic heat disturbing the heart; if disturbed sleep is accompanied by dizziness, timidity, nausea and bitter taste in the mouth, it is caused by gallbladder depression and phlegm disturbance.

Dreaminess
The cause and pathogenesis of dreaminess are almost the same as that of insomnia. Dreaminess and insomnia usually appear at the same time and can be treated with the same kind of drugs. Therefore, diagnosis of dreaminess can be made according to that of insomnia.

Somnolence
Somnolence refers to sleepiness in both daytime and night. Somnolence is often seen in diseases of yang asthenia and yin predomination as well as internal exuberance of phlegmatic dampness. For example, somnolence accompanied by lassitude, heaviness of head and eyes, oppression and fullness of the chest and heaviness of the limbs is usually caused by internal exuberance of phlegmatic dampness and failure of lucid yang to rise postscript somnolence accompanied by spiritual lassitude, reduced appetite and indigestion is often due to insufficiency of gastrosplenic qi and failure of the spleen to transform and transport; spiritual lassitude and somnolence following serious disease are signs of healthy qi failing to be restored.