Difficult to say, as I, like many others, experienced multiple traumas that began in infancy. Looking back, though, there was a definite spike in what I now see as PTSD symptoms when I was about 23 -- at the time, my parents separated in a violent fashion, and I was starting psychotherapy. As often happens, therapy (with a wonderful, sturdy and willing-to-go-deep therapist) allowed long-repressed emotions, flashbacks and memories to emerge with all the subtlety of an erupting volcano!
I find it interesting that the condition is always known as post-traumatic stress disorder. The traumas themselves are excessive stresses. Sometimes it's hard to discern what's "post-" and what's not. In my own case, there was recently a two-year period of chronic stress/trauma ... so there were symptoms both during and afterward. The breaking point arrived with one event ... and then there were symptoms that were more identifiable as post-traumatic stress. It seems to me that symptoms during that two-year period were repressive --> I was hanging on, getting through, continuing to work and function until I became actively ill. The symptoms that arrived after the source of stress was removed (in this case, brutal, violent next-door neighbours from hell) were more expressive --> panic, outbursts of crying, dissociation, etc.
