"Depression is a mood disorder that causes a persistent feeling of sadness and loss of interest... it affects how you feel, think and behave and can lead to a variety of emotional and physical problems. You may have trouble doing normal day-to-day activities, and sometimes you may feel as if life isn't worth living. More than just a bout of the blues, depression isn't a weakness and you can't simply "snap out" of it. Depression may require long-term treatment... Most people with depression feel better with medication, psychological counseling or both."
-"Depression: Definition" by The Mayo Clinic Staff