The word depression is used for a wide range of mental states. On one side are passing moods of disappointment, regret, or anxiety that almost everybody has at one time or another. For many of us, Sunday evenings are depressing in this sense, because the weekend is over and the responsibilities, pressures, and uncertainties of the week lie ahead.
On the other side is so-called clinical depression, a harrowing week-after-week emotional despair that is a major health disorder. Although there is a huge gap between an occasional case of Sunday blues and a deep clinical depression, the difference is not in the kinds of moods but in their intensity and duration.
Doctors make a diagnosis of clinical depression when a person suffers most or all of a group of symptoms for longer than two weeks. These include despair, bouts of uncontrollable weeping, lethargy, self-hatred, exhaustion, hypochondria, and, in extreme cases, delusions and hallucinations. A paralysis of will can make the clinically depressed person incapable of functioning at home or at work, at times even unable to get out of bed. Those who suffer from clinical depressions can often see no end to their pain and no prospect of happiness in the future.