In layman's terms, a single episode of depression is also called a single episode of major depressive disorder, which means that it only occurs once and there are no manic symptoms, mixed depression symptoms, or hypomanic symptoms. The first time a person suffers from depression and has the above symptoms is also called a single episode of depression, because it is unknown whether the patient will have the disease in the future. If the disease recurs, it is called recurrent depression. Single episodes of depression are divided into three types according to the severity of the disease. What are the three types? 1. Mild depression (mild depression) In addition to no damage to social function or only mild damage, the episode that meets all the criteria for a depressive episode is called mild depression; 2. Depression without psychotic symptoms In addition to meeting the symptom criteria for a depressive episode, there are also psychotic symptoms such as hallucinations, delusions, or tension syndrome, which is called depression without psychotic symptoms; 3. Depression with psychotic symptoms In addition to meeting the symptom criteria for a depressive episode, there are also psychotic symptoms such as hallucinations, delusions, or tension syndrome, which is called depression with psychotic symptoms;