Regarding the startle reflex: for years I considered my startle reflex to be part of PTSD. It is extreme. One time while walking as a tourist, a friend behind me took a map out of my back pocket. I spun around and instantly assumed a hand combat stance, ready to kill. Scared everybody, except my kids, who have learned to laugh it off. Fortunately, a couple years ago, a therapist took me through about 6 weeks of Eye Movement Desensitization and Reprocessing, which looks kinda like hypnosis. My nightly nightmares and daily violent thoughts went away. Woohoo! Cured. Almost, I still have the startles. One evening recently in a movie theater, the bad guy shot in the direction of the audience. I instantly leaped out of my seat and began to jump over the seats, as though I were going to attack the movie screen. Most of my startles are tiny and not dramatic.
So it seems there are a huge number of causes for startles.
