Depression is a state of low mood and aversion to activity that can affect a person's thoughts, behaviour, feelings and physical well-being. Depressed people may feel sad, anxious, empty, hopeless, helpless, worthless, guilty, irritable, or restless. They may lose interest in activities that once were pleasurable, experience overeating or loss of appetite, or problems concentrating, remembering details or making decisions; and may contemplate or attempt suicide. Insomnia, excessive sleeping, fatigue, loss of energy, or aches, pains or digestive problems that are resistant to treatment may be number of psychiatric syndromes feature depressed mood as a main symptom. Mood disorders are a group of disorders considered to be primary disturbances of mood. Within them, major depressive disorder (MDD), commonly called major depression, or clinical depression, is a condition where a person has at least two weeks of depressed mood or a loss of interest or pleasure in nearly all activities. Dysthymia is a state of chronic depressed mood, the symptoms of which do not meet the severity of a major depressive episode. People suffering bipolar disorder may also experience major depressive the mood disorders, dysthymia is also commonly a feature of borderline personality disorder. Adjustment disorder with depressed mood is a mood disturbance appearing as a psychological response to an identifiable event or stressor, in which the resulting emotional or behavioral symptoms are significant but do not meet the criteria for a major depressive number of psychiatric syndromes feature depressed mood as a main symptom. Mood disorders are a group of disorders considered to be primary disturbances of mood. Within them, major depressive disorder (MDD), commonly called major depression, or clinical depression, is a condition where a person has at least two weeks of depressed mood or a loss of interest or pleasure in nearly all activities. Dysthymia is a state of chronic depressed mood, the symptoms of which do not meet the severity of a major depressive episode. People suffering bipolar disorder may also experience major depressive the mood disorders, dysthymia is also commonly a feature of borderline personality disorder. Adjustment disorder with depressed mood is a mood disturbance appearing as a psychological response to an identifiable event or stressor, in which the resulting emotional or behavioral symptoms are significant but do not meet the criteria for a major depressive episode.文字来源是维基百科,请自己根据需要删节吧