1.Broad sense of old age depression disorder Broad sense of old age depression disorder refers to the depressive disorders seen in old age (usually greater than or equal to 60 years old) of this specific group of people, including both the first onset of old age depression disorder, also includes the onset of old age before the continuation of old age or old age recurrence of depression disorder, also includes a variety of secondary depression disorders seen in old age; 2.Narrow sense of old age depression disorder Narrow sense of Depressive disorder in old age refers specifically to the primary depressive disorder with first onset in old age, with persistent depressed mood as the main clinical manifestation and clinical features of depressed mood, anxiety, sluggishness and a wide range of somatic discomfort. Mental disorders cannot be attributed to physical illness or organic brain pathology. Generally, the course of the disease is long, with a tendency to remission and relapse, and some cases have a poor prognosis and can develop into refractory depression. 3.Characteristics of depressive disorder in old age The age of onset of monophasic depressive disorder has a bimodal distribution, with another peak of onset after the age of 50. In all patients with depressive disorder in old age over 65 years old, about 2/3 of them have late onset. The first onset of depressive disorder in old age reaches more than 40-50%. Bipolar disorder, on the other hand, is very rare. The prevalence of depressive disorders in old age in Beijing is 12.89%, with 10.43% in men and 16.89% in women. There are numerous differences between monophasic depressive disorder in old age and young adulthood. It is thought that geriatric depressive disorder may be a subtype of mood disorder and the name late-onset depression is suggested. It is one of the most common functional disorders in old age. However, epidemiological studies on depression in old age are still relatively few. It accounts for 7.59%-7.36% of all annual geriatric primary cases. Hospitalized patients account for 21%-54% of all geriatric mental disorder patients. As people’s life expectancy increases, the absolute number and proportion of elderly people suffering from depressive disorders will grow accordingly. Depression has become one of the major problems that seriously affects the mental health of the elderly. Another problem closely related to depressive disorders is suicide. The death rate of suicide and attempted suicide among the elderly is 4.8 per 10,000, which is the fourth highest among 39 countries reported to the World Health Organization, with the death rate of suicide among rural elderly women being more than three times that of urban elderly women, and the death rate of suicide among rural elderly men being four times that of urban elderly men. The diagnosis of depressive disorders in the elderly is more complicated than in young adults because of the special characteristics of the physical, psychological, and social relationships of the elderly; on the other hand, the treatment of depressive disorders in the elderly is much more complicated than in young adults because of the physical illnesses that often accompany them and the changes in their physiological conditions.