Depression is a state of low mood and aversion to activity that can affect aperson's thoughts, behavior, feelings and physical well-being. Depressed people may feel sad, anxious, empty, hopeless, worried, helpless, worthless, guilty, irritable, or restless. They may lose interest in activities that once were pleasurable; experience loss of appetite or overeating, have 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 present.

Life events

Life events that may precipitate depressed mood include personal conflicts or disputes with family members or friends, bereavement, moving, losing a job or income, divorce, stress, retirement, menopause,social isolation, and social rejectio

Medical treatments

Certain medications are known to cause depressed mood in a significant number of patients. These include Hepatitis C drug therapy and some drugs used to treat high blood pressure, such as beta-blockers or reserpine.

[edit]Non-psychiatric illness

Depressed mood can be the result of a number of infectious diseases and physiological problems includinghypogonadism (in men), Addison's disease, Lyme disease, multiple sclerosis, sleep apnea and disturbed circadian rhythm. It is often one of the early symptoms of hypothyroidism (reduced activity of the thyroid gland). For a discussion of non-psychiatric conditions that can cause depressed mood, see Depression (differential diagnoses).

[edit]Psychiatric syndromes

A number of psychiatric syndromes feature depressed mood as a main symptom. The mood disorders are a group of disorders considered to be primary disturbances of mood. These include major depressive disorder (MDD), commonly called major depression or clinical depression, where a person has at least two weeks of depressed mood or a loss of interest or pleasure in nearly all activities; and dysthymia, a state of chronic depressed mood, the symptoms of which do not meet the severity of a major depressive episode. Another mood disorder, bipolar disorder, features one or more episodes of abnormally elevated energy levels, cognition and mood, but may also involve one or more depressive episodes.

Outside the mood disorders: borderline personality disorder commonly features depressed mood; 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,^[4] and posttraumatic stress disorder, an anxiety disorder that sometimes follows trauma, is commonly accompanied by depressed mood.