5-Hydroxytryptamine, also known as serotonin, is present in the mucous membrane of the digestive tract in about 90% of the human body, and only 1%-2% in the brain. Due to the existence of the blood-brain barrier, it is difficult for 5-hydroxytryptamine in the blood to enter the brain. 5-Hydroxytryptamine in the brain, as a neurotransmitter, is mainly distributed in the pineal gland and hypothalamus of the brain. Current research suggests that 5-hydroxytryptamine can be involved in controlling mood, anxiety, regulating sleep, body temperature, appetite, sexual behavior, exercise, cardiac blood-to-tube function, and pain perception. Depression and anxiety are common mood disorders, mostly caused by psychogenic factors (such as major trauma or persistent mental stress or adverse environment, lack of good lifestyle habits), organic factors (such as various organic diseases of the body) and other factors that cause a decrease in the level of norepinephrine and 5-hydroxytryptamine in the brain. When 5-hydroxytryptamine and norepinephrine content in the brain is reduced, the following symptoms may occur: 1. Sleep disorders: difficulty falling asleep, early awakening, dreaminess, superficiality, and no sense of recovery after waking up; 2. Depressive symptoms: easy fatigue and weakness; moodiness, frequent crying or feeling of aggression; loss of interest in daily life, no sense of pleasure; poor concentration and memory loss; low self-assessment, self-blame, or guilt; in severe cases (3) Anxiety symptoms: frequent and inexplicable nervousness and uneasiness; irritability, irritability, irritability; fear and apprehension; (4) Somatic symptoms: (1) Nervous system: headache, dizziness, tinnitus, tinnitus, numbness of the face, lips or hands and feet, tightness or foreign body sensation in the throat; (2) Respiratory system: difficulty in breathing or breath-holding, hyperventilation; (3) Gastrointestinal symptoms: abdominal pain (4) somatic pain or discomfort: head, neck, back and limbs; (5) genitourinary system: frequent urination, urinary urgency, loss of libido; (6) cardiovascular system: chest tightness, palpitations, intermittent hypertension, tachycardia, arrhythmia, and even a sense of dying; (7) sympathetic symptoms: dry mouth, excessive sweating, chills or fever in the body. Therefore, insomnia is often a symptom of anxiety and depression. Treatment of insomnia alone can only treat the symptoms but not the root cause. In contrast, antidepressant treatment can fundamentally improve the above four major categories of symptoms by regulating norepinephrine and 5-hydroxytryptamine function, therefore, antidepressant treatment is currently mostly used for insomnia patients.