I have this theory that in my case, my anxiety disorders arise at least partially from the fact that I have above average intelligence. (Like how Matilda has superpowers. Except my superpowers look like this. [Scroll down to Take #5; this was before I started using Jen's awesome HTML anchors.]) Basically, my brain has a LOT of processing power, and its preference is to devote that processing power to imaginative pursuits. (This is why I hate math even though I'm good at it.) When my brain isn't occupied by something creative, it sort of turns on itself and starts devising elaborate scenarios about how WE'RE ALL GONNA DIE!!11!
I am posting this mainly so I can refer to it later. Be prepared. (But don't hold your breath. That's bad for you.)