I think with PTSD comes hyper-vigilance, which it considered different from paranoia.

I'm not fully sure of the difference but my T always seems to stress there is one. I think it's something like paranoia is when it's without cause, and hyper-vigilance is from past experience and not as "paranoid" as paranoia. I could be completely off base here, though, and wrong.

It's common to me and I'm pretty certain that fear is common amongst many people with PTSD- although I also have a paranoid personality type diagnosed to me, which is where the difference between paranoia/hyper-vigilance comes into play.

Take care- safe hugs if okay?