How to diagnose a patient as depressed in clinical practice can be understood in three ways. In the first aspect, depression is considered when there is a persistent low mood that lasts for about two weeks or more, during which four of the following symptoms are present: first, loss of interest in daily activities or life, no sense of enjoyment; second, significant loss of spirit and energy, unexplained persistent fatigue; third, significant reduction in psychomotor retardation; fourth, low self-esteem, self-blame and guilt to the extent of delusions; fifth, difficulty in association and a significant decrease in the ability to think consciously; sixth, recurrent thoughts of death or suicidal behavior; seventh, insomnia, early awakening, or excessive sleep; eighth, loss of appetite or weight loss; and ninth, a significant decrease in sexual desire. The second aspect is that the mental disorder causes at least one of the following: first, impaired social functioning; second, distress and adverse consequences for the person. In the third aspect, the following diseases were excluded: e.g. organic brain disease, somatic diseases, psychotic disorders due to psychoactive substances, and schizophrenia. Meeting some of the entries in the above three aspects will determine if one has depression.