Mood disorders are also known as affective disorders or depressive disorders. These illnesses share disturbances or changes in mood, usually involving either depression or mania (elation). With appropriate treatment, more than 80% of people with depressive disorders improve substantially.
Major depression – an extreme or prolonged episode of sadness in which a person loses interest or pleasure in previously enjoyed activities
Bipolar disorder (also referred to as manic-depressive illness) – alternating episodes of mania ("highs") and depression ("lows")
Dysthymia – continuous low-grade symptoms of major depression and anxiety
Seasonal affective disorder (SAD) – a form of major depression that occurs in the fall or winter and may be related to shortened periods of daylight