Everyone gets the blues or feels sad from time to time, or feels intense grief brought about by the loss of a loved one. These feelings are an unavoidable but normal and temporary reaction to life's stresses. There is a point at which a combination of the intensity and duration of emotion and symptoms indicates that depression has ceased to be a temporary mood and has become a clinical state.
Depressive disorders come in various forms.
Some people who suffer from a major depressive disorder have symptoms so severe that they are unable to function at all. Some have bipolar disorder, experiencing cycles of terrible lows and inappropriate highs. Depressive disorders are the most prevalent of the mental illnesses, but are also the most responsive to treatment. Causes The causes of depression are not yet known. In the past 10 years, compelling evidence has established that depressive disorders run in families.