Depression is a mental disorder characterized by a significant and persistent depression with corresponding abnormalities in thinking and behavior. The main manifestation of depression is depression, which is what we usually call bad mood, unable to be happy, unable to lift the spirit. Patients often show sullenness and sighing. The depressed mood is accompanied by abnormalities in thinking and behavior, such as slowing down speech, feeling inflexible, weak and inactive, not wanting to do anything, or even sitting alone or sleeping in bed all day and not interacting with others. Depressed mood is the core symptom of depression. Most people define depressed mood as sadness, pain or depression, described as if a dark cloud is about to descend. Anxiety Disorders Anxiety symptoms are predominant, with excessive worrying at the core of anxiety symptoms. Depression and anxiety often occur together, and depression can be co-morbid with anxiety, and if present together can be diagnosed as both depression and anxiety. The key to differentiation is whether the two symptoms exist and disappear at the same time. If anxiety symptoms are predominant and primary, anxiety disorder is still diagnosed despite the presence of depressive symptoms; if depressive symptoms are predominant and dominant, the diagnosis of depression cannot be changed despite the presence of anxiety symptoms.