Definition: Although most people may feel down from time to time, few of these people are actually suffering from what psychologists consider depression. Depression is a mental illness, classified by psychologists as a mood disorder. It affects a person's mood, how she thinks and even how she feels physically. Generally, doctors will make a diagnosis of depression if someone has suffered for an extended period of time (two weeks or more).
History: Depression is not a new phenomenon; rather, it has been well documented throughout history. In ancient times, people believed that mental illness was caused by supernatural forces. To rid the person of their illness, many may have practiced trephanning, which required holes to be cut into the afflicted person's head in order to let evil spirits out. The Greeks later explained mental illness in terms of four major humors, or fluids in the body. According to this theory, melancholia (or depression) was caused by an excess of black bile (the humor connected to the element of air) in the body.
