My cousin who is 38 now is a war vet. He was a paratrooper in Iraq and was lucky to escape alive, relatively unscathed, considering what happened to his friends. It's a truly awful thing, to see that happen to your friends. It most definitely gave him PTSD and he definitely gets paranoia nowadays. He's got four guns in his house, one of which is a Glock that he puts under his pillow at night. The other three are in hidden areas (which he won't say) "in case someone breaks in and tries to stab me, I will be able to quickly grab a gun." He's constantly paranoid like that. And he's afraid that someone is watching him 24/7 and that he has to "be prepared to escape." He thinks there are cameras, the FBI, etc..

The PTSD hits him real hard and it's heartbreaking.

So imo, I think PTSD can trigger paranoia and vice versa. You could be experiencing both like he does... because I've definitely seen it before. He just gets afraid of little things because they remind him of the PTSD, and that in turn triggers paranoia. Things just ramp up pretty quick with him. He's permanently disabled for those reasons, and he uses his disability money to stock up on protective weapons.