Steve Peterson points out you rarely see clinical depression in movies and TV. Which is odd, considering it’s much more common in real life than, say, retrograde amnesia.
What makes clinical depression un-cinematic is that it’s a negative affect: it’s characterized by a lack of motivation, a lack of action. Great writing can only do so much when you have a protagonist who doesn’t want to protagonate.
Shortbus has a clinically depressed character who goes off his meds — a decision that is as frustrating in a movie as it is in real life. While the character explains himself fairly well, he’s kind of a drag to be around. Again, realistic, but not particularly cinematic.