<P> Major depressive disorder ( MDD ) , also known simply as depression , is a mental disorder characterized by at least two weeks of low mood that is present across most situations . It is often accompanied by low self - esteem , loss of interest in normally enjoyable activities , low energy , and pain without a clear cause . People may also occasionally have false beliefs or see or hear things that others can not . Some people have periods of depression separated by years in which they are normal while others nearly always have symptoms present . Major depressive disorder can negatively affect a person 's personal , work , or school life , as well as sleeping , eating habits , and general health . Between 2 -- 7 % of adults with major depression die by suicide , and up to 60 % of people who die by suicide had depression or another mood disorder . </P>
what does single episode major depressive disorder mean
a mental disorder characterized by at least two weeks of low mood that is present across most situations