I think I experienced it from the other side of the fence about 2 months ago, when I started seeing this guy who admitted that he thought he might have ptsd after his 'friends' beat the crap out of him one time when he was tripping on acid. That's gotta be pretty traumatic I'd guess.
He hasn't had a diagnosis, but all the symptoms are there, and he is extremely touchy and takes things I say the wrong way. It's like walking on eggshells, and one time I brought him a cup of tea and responded to something he said, which sounded like he was about to bite my head off...and I backed away, only to have him tell me to get out of his room??
He took something I said the wrong way and thought I was accusing him of something. I was so confused, and I think it was him feeling insecure because he liked me a lot, and we were getting quite close, quite quickly. I backed off and stopped going around there regularly. I see him now once in a while, as a friend only.
It feels terrible to be the one on the receiving end of someone who is suspicious of my motives, purely based on things I say that are taken the wrong way.