Most people have felt sad or depressed at times. Feeling depressed can be a normal reaction to loss, life's struggles, or an injured self-esteem.
But when feelings of intense sadness -- including feeling helpless, hopeless, and worthless -- last for days to weeks and keep you from functioning normally, your depression may be something more than sadness. It may very well be clinical depression -- a treatable medical condition.
WebMD. (2009, September 12). Retrieved from http://www.webmd.com/depression/guide/what-is-depression