I discovered RSD only in the last year or so and it has made so much sense of our family dynamics. I have wondered about the roots of it as well, and your perspective is in line with my own suspicions. I can see the origin of my own RSD in significant rejection by a parent in early childhood. On the other hand, my daughter, who has grown up in an accepting, loving family, has shown extreme sensitivity to things like perceived negative tone of voice from a young age, even without as many obvious rejections in her life. We're an entire family of NDs trying to learn to manage these big emotional reactions.