major depressive disorder

n. A disorder characterized by two or more episodes of depressive episodes which are periods between 2 weeks and 6 months in which the person feels depressed, low in energy, worthless, and guilty most of the time; lacks interest and pleasure in daily activities; has disturbed sleep and/or appetite, psychomotor agitation or retardation; has diminished capacity to concentrate and indecisiveness; and thinks often about death and suicide.