MODEL RELEASED. Depression. Close-up of the downcast, forlorn face of a depressed man. Most people experience the symptoms of mild depression, such as excessive sadness or despair, at some point in life. The condition is not classed as a serious psychiatric illness, however, unless the patient's behaviour or physical state is affected, causing loss of sleep or appetite, for example. Treatment for severe depression includes psychotherapy and antidepressant drugs, and is usually very successful.