I. Symptom Criteria: Depressed mood mainly, and at least four of the following: 1. loss of interest, no sense of pleasure; 2. loss of energy or fatigue; 3. psychomotor retardation or agitation; 4. low self-esteem, self-blame, or feelings of guilt; 5. difficulty in association or reduced ability to think; 6. recurrent thoughts of death or suicidal or self-injurious behavior; 7. sleep disorders, such as insomnia, early awakening, or 8.Decreased appetite or significant weight loss; 9.Decreased sexual desire. Severe criteria: Impaired social function, causing pain or adverse consequences to the person. 3. Duration of the disease: the symptoms and severity criteria are met for at least 2 weeks. Exclude organic mental disorders, psychoactive substances and non-addictive substances caused by depression.