The cartoon below put me in mind of Joseph Heller's quote above from Catch 22. Both make the same point, that being told you're being irrational doesn't help, if you believe either (a) that you're a fraud or (b) that they're "after you".

What does help with Imposter Syndrome, however, is the counsel of your peers. We have found that requesting approval, in advance of publishing on the internet helps brilliant but insecure experts enormously. Having a few helpful and encouraging words can make the world of difference. 

As for the paranoia... you're on your own.