It is a sickness just as are heart disease, respiratory ailments and the common cold. Like other diseases, it may range in severity from very mild and short-lived to severe and debilitating. This is when an individual has a single bout with depression. It is usually milder than other forms of depression, and often gets better on its own without any intervention. It may also be caused by changes in the body as it matures, or as a symptom or other illness.
Depression sometimes follows an injury, particularly to the head.
When an individual has a history of depression that keeps 'coming back' again and agian, it is called recurring episode. It is more serious than the single episode type of depression and could indicate ongoing stressors that are not effectively dealt with, or a biochemical imbalance. Chronic This is depression that just won't go away. It has lasted a long time, and is not getting any better. This depression may be most debilitating, and can interrupt family life, careers and possibly lead to suicidal ideations.