I am highly sensitive also, and have read the book (The Highly Sensitive Person). It made a lot of sense to me. One of the things the book does is helps you to see that if you have these traits, it doesn't mean that anything is wrong with you, and they aren't things to try to change but to understand and recognize the benefits as well as the things that you may need to adjust for. I think that a lot of people who are highly sensitive tend to be labled and given diagnoses that may be unwarranted, and sometimes they may develop disorders in response to the way they are treated and/or assume that they are expected to act.

It wouldn't surprise me at all if highly sensitive persons are more susceptable to certain disorders such as PTSD.