ABSTRACT
Depression is a term that refers both to a transient mood state and a clinical syndrome or disorder. As a mood state, depression is characterized by feeling despondent or unhappy, while depression as a mood disorder is a persistent set of symptoms as described in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM IV). Specifically, major depressive disorder (MDD) is a psychiatric condition in which diagnostic criteria require five or more depressive symptoms, one of which must include either depressed mood or loss of interest or pleasure. Other depressive symptoms include significant weight loss, sleep changes (i.e., insomnia or hypersomnia), psychomotor agitation or retardation, fatigue or loss of energy, feelings of worthlessness or excessive guilt, diminished ability to think or concentrate, and recurrent thoughts of death. MDD is also distinguished from normal symptoms of sadness by criteria for symptom severity and duration: symptoms of depression must have been present during the same two-week period, be present all or most of the time, and represent a change from a previous level of functioning.
