The recovery rate of first-episode depression is around 70%, and about 30% of patients are refractory patients i.e. cases in which the use of two or more antidepressants of different chemical structure does not work after sufficient doses for sufficient time (more than 6 weeks). Persistent depression, chronic depression, double depression, atypical depression, psychotic depression, geriatric depression, co-morbid problems, etc. are common. Treatment principles: 1. emphasis and intensive psychotherapy; 2. increase the dose of drugs; 3. extend the duration of use; 4. change the route of medication; 5. antidepressant booster therapy; 6. antidepressant combination therapy; 7. electroconvulsive therapy application; 8. transcranial magnetic stimulation therapy; 9. phototherapy, sleep deprivation therapy.