The criteria for depression are generally met when the depressed mood has persisted for more than 2 weeks. Depression is a disease with significant depressed mood as the main clinical manifestation and is classified as mild, moderate and severe depression. Patients with depression often show poor mood, distress and sadness, and even pessimism and despair. Patients are worried and depressed all day long, and even spend their days like years. Some patients may be nervous and anxious, and they may lose their enthusiasm and joy for life and lose interest in life. If these symptoms persist for more than 2 weeks, depression is suspected. The effects of depression are large. Mild depression may cause a person to be in a depressed, inhibited state. In case of severe depression, suicidal thoughts and behaviors, or even extended suicidal behaviors may occur, and such disorders are prone to further aggravation. Therefore, if a patient has the above symptoms, regardless of the severity, it is recommended to promptly seek systematic and standardized treatment in the psychology department.