Yes, but the LESSON was for medical, in which we commonly use "Depression" as a diagnosis. Doctors would say, "You're depressed," but write as a diagnosis, "Depression," not "A depression." I think that if a Hispanic person said, "Oh, my poor friend; he has a depression," I would be waiting to hear if he had a dent in his head.
Looks like it can mean several things, from physical to emotional. A depressed financial market, a depression left by pressing into something, the medically diagnosed depression. http://www.spanishdict.com/translate/una%20depresion