Thank you for this post, DeLellis. I suffer from most, if not all, of the symptoms listed for DPAFU. I've experienced depersonalization and derealization before, and I think I was oversimplifying them as only feeling like I or the world around me isn't real. The part that especially rings true for me at the moment is the bit about "spend[ing] excessive amounts of time worrying about abstract, existential, metaphysical or hypochondriacal issues, such as the meanings of words, how other people experience the world, the meaning of life and concepts of space and time." So often I find myself wondering about these kinds of things. What is reality? What are we as people? Why are we here? How did we come to be here? The whole concept strikes me as so strange and alien that it scares me. Also, the feeling of disconnection is where I think my worries about delusions come from. I'm constantly "testing" myself to see if I believe in certain things, and when I can't clearly see the answer, it scares the living daylights out of me. The minute my anxiety starts to fade, though, the worries about being delusional usually do, too.
I'm going to see if I can order the book recommended on the page. I've always wanted to try CBT, and I think this could be very helpful.