I've never been diagnosed with either TPI or PTSD, but my T believes I probably manifested characteristics of both in the aftermath of what happened to me. It's all hindsight, but I think there is something to it.
From what I understand, TPI is often stress-induced. I was under tremendous stress from being in a new school just a couple of weeks after my CSA experience. I had trouble with other kids...normal stuff like being relatively well-liked at my old school to being a nobody at the new school. While I did have a problem with a couple of other kids, I withdrew behind walls, because I trusted no one. I even pulled away from my parents. I didn't trust anyone. I kept my guard up all the time...and like you said, the apparent threat would pass and I was left wondering why I was so worried.
This coupled with out of control ADHD led to some really impulsive behavior. I know there is a danger of second guessing everything, but to this day I think two other things happened that made things worse.
First, I had a pretty severe concussion from playing football. Second, that same tackle that gave me a concussion also tore the meniscus in my left knee. A week or so later, I had surgery to repair the knee. After anesthesia, I was in a fog for several days. I know that I have no empirical evidence, but I believe the concussion, anesthesia, and ADHD converged after the CSA to make me more paranoid and impulsive. I was nervous...and at times withdrawn. Previously, I was more of an extrovert and a talker. I'd talk to anybody about anything. Add testosterone to the mix, and I was a moody, impulsive teenage boy who didn't take guff from anyone, even though I was afraid of the shadows in my room at night---like a toddler might be.
Here's what happened:
My parents noticed and took me to see a psych. because they thought I wasn't adjusting to the move we just made.I never mentioned the CSA. I played up the move and deflected suspicion away from anything else. The psych. Prescribed Elavil and Ritalin later on.
The Elavil managed to make me impotent...as a teenager! I got off of the stuff and stayed on Ritalin for the ADHD. The reason I mention this is that while my ADHD is under control, I'm less impulsive AND less likely to experience any PTSD-like symptoms--including TPI. I'm not saying I had/have either one, but I do recognize some of the classic traits associated with them.
As I got older and out of college, I stopped taking ADHD meds for a long time since that is a kid's disorder, right? Wrong. As I took on more job responsibilty, the ADHD issues of concentration and impulsiveness came back...and not so coincidentally, so did all of the CSA issues that had been buried. I pulled away and put up walls again until I couldn't do it any longer. That's when I told my wife, joined MS and saw a T about it. The T recognized the ADHD... I started medicating that again. Doing so really helped me focus on work, family, and taking on the CSA.
Sorry to ramble, but that's my take on it.
"His voice rose under the black smoke before the burning wreckage of the island; and infected by that emotion, the other little boys began to shake and sob too. And in the middle of them....Ralph wept for the end of innocence, the darkness of manâ€™s heartâ€¦â€ť. -----William Golding