I've noticed this since at least 2004 (and I wasn't paying that much attention to conventional voters before that). I've called it the post election hangover that generally lasts until February, and is strongest when it's over a POTUS (obviously, I just mean the USA, I don't know about other places). If a choice lost then it was like grief and despair. I hated seeing this in people as it seemed like suffering for no real point, and I've read of people committing suicide over it. And it can happen even in the primaries (and I've also read of assaults, like brothers or brother-in-laws who attacked each other, one stabbing the other, because they argued over dinner whether Hillary or Obama would be the one who should run in 2008). My grandmother has a common rule that politics (and religion) are not discussed while eating because of how badly it can upset people over what many others would consider trivial, or at least not worth getting worked up over.
This one has been the worst, by far. But then I was noticing a big difference even BEFORE the election.
Strangely, issues normally provoke less of a reaction. But then it's interesting how many cared about wars when Bush was POTUS but then those big crowds dried up overnight to the point it was easy to overlook the very few left after Obama won. I don't get it, but it's apparently part of how partisan politics are more important than ethics or issues, something MAD Magazine has done a lot of parodies over so I know it's not just me seeing it. This makes me think it's a tribal thing (I'm speaking of instincts) as opposed to ideals, and probably in the same region of the brain that gets excited or depressed depending on how one's sports team does (which people can get equally crazy about). It's not so much about the issues but who one identifies with, and if their choice loses then they feel rejection at a personal level by their country, and may even feel threatened at an instinctual level.
As for what PBSD is, I'm gonna guess Post Buffy Stress DO 😛