Depression is not a mere psychological problem, it is a disease. In the World Health Organization, in the United States, and in the two mainstream diagnostic criteria that we use internationally, depression is undoubtedly an important disease classification and definitely belongs to the disease. Of course, among the treatments for depression, psychotherapy is a very effective treatment. But it does not mean that depression is a psychological problem rather than a mental problem. In the classification of mental illness, depression is a major mental disorder. Unlike some psychological disturbances encountered in the general population, it is clearly a disease, and a relatively serious disease. From the socio-economic point of view, the disease point of view, the symptoms of the disease and the functional damage caused to the patient, depression is not a trivial matter from any point of view. It can be a significant burden to the individual and to society. On the bright side, severe does not mean difficult to treat, and most depressions are able to return to their pre-morbid condition after treatment.