Depression is mainly characterized by low mood, during which at least four of the following symptoms are present and persist for more than two weeks, it is recommended to seek medical treatment. 1. The degree of depressed state of mind varies and can range from a mildly poor state of mind to sadness, pessimism and despair. Patients feel heavy, life is not meaningful, happy, depressed, spending time like years, painful, can not be self-reliance. Some patients may also appear anxious, easily agitated, nervous and restless. 2.Loss of interest is one of the common symptoms of depressed patients. Loss of enthusiasm and pleasure in life and work, and loss of interest in everything. The patient does not experience the joy of family, does not care about the past hobbies, often lives alone behind closed doors, alienates friends and relatives, and avoids social life. Patients often complain of “no more feelings”, “emotional numbness”, “no more happiness”. 3. Loss of energy, fatigue and weakness, difficulty in washing, dressing and other small tasks of life, and inability to cope with them. Patients often use the words “mental breakdown” and “deflated ball” to describe their condition. 4. Low self-evaluation: Patients tend to excessively depreciate their own abilities, and look at their present, past and future in a critical, negative and negative manner, saying that they are useless and their future is dark. Strong feelings of self-blame, guilt, uselessness, worthlessness, helplessness, and in severe cases, self-criminality and suspicion may appear. 5.Patients show significant, persistent and generalized depression: difficulty in attention, memory loss, slow brain, closed mind, slow action, but some patients show restlessness, anxiety, tension and agitation. 6, negative pessimism: very painful, pessimistic, despair, feel that life is a burden, not worth staying, to die for relief, may produce strong suicidal thoughts and behavior. 7, physical or biological symptoms: depressed patients often have biological symptoms such as loss of appetite, weight loss, sleep disorders, low sexual function and diurnal fluctuations in mood, very common, but not in every case. (1) Loss of appetite and weight loss: Most patients have poor appetite, poor appetite symptoms, delicious food is no longer tempting, patients do not think about tea and food or tasteless, often accompanied by weight loss. (2) Loss of sexual function: Early in the course of the disease, the libido may be reduced, men may experience impotence, and female patients may experience a loss of sensuality. (3) Sleep disorder: The typical sleep disorder is early awakening, 2 – 3 hours earlier than usual, not falling back to sleep after waking up, and falling into a sad atmosphere. (4) Diurnal variation: The patient’s state of mind has a change of heavy day and light night. Early in the morning or in the morning, the patient falls into a low mood, and in the afternoon or evening, the patient gradually improves and is able to have a short conversation and a meal. The incidence of diurnal variation is about 50%.