Unipolar depression is the most common mood disorder and is generally characterized by a dismal, dark view of life lasting at least two weeks.  Depressed persons may feel that the simple tasks of everyday life are overwhelming.  A sufferer of unipolar depression must have no history of mania (a highly elevated, euphoric mood lasting at least one week), and her mood will return to normal following a depressed episode.  In the United States, approximately 7% of adults have a severe episode of depression each year, and 5% of adults experience mild forms.  Depression may begin at any age, but the median age for a depressed person in the United States is 34.  The condition is twice as common in women as in men, and varies greatly over specific populations (see Sociocultural Perspective under the Etiology link for more information).  Anyone who suffers from a major depressive episode without a history of mania is diagnosed with major depressive disorder.  Dysthymic disorder is another type of depression which lasts for two years but is milder than major depressive disorder.