Feeling sad and blue occasionally is completely normal. These feelings are uncomfortable, but are temporary and are not something that prevents us from doing our work or enjoying life. Depression is a mood that goes beyond normal everyday sadness. It is an illness that affects thoughts, feelings, physical well-being, and families.
Roughly 25 million Americans have at least one major depressive episode per year. Without treatment, the symptoms may only increase. The different forms of Depression include:
Major Depressive Disorder
Dysthymic Disorder
How to identify and Treat Depression
This video by the Ministry of Health in Israel is a very good overview of what depression and treatment for depression are. It's a little over 9min long and gets right to the point. Worth watching.
Dr. Sapolsky on Depression
This video is almost an hour long, but if you're looking for an in-depth lecture on what Depression is both psychologically and biologically, you won't find much better than Dr. Sapolsky from Stanford University.