Reading your comments, I can relate. I never found an answer but ptsd, derealisation and schizophrenia all feel like they overlap or fit on a spectrum. Perhaps some of us don't quite have the ingredients to completely detach from reality and can manage our way around symptoms. A lot of the time I think I'm just too imaginative.

If I'm quite upbeat and have good happy mood (not so common) then symptoms are much less likely to occur, so it could also be a depressive state of sorts.