Depression
A mood disorder involving disturbances in emotion (excessive sadness), behavior (apathy and loss of interest in usual activities), cognition (distorted thoughts of hopelessness and low self-esteem), and body function (fatigue, loss of appetite). Symptoms extend into many parts of an individual's life and include lack of interest in daily activities, decreased motivation, feelings of worthlessness, and sometimes suicidal thoughts.See also Childhood Depression, Bipolar Disorder / Manic Depression and Mania