I'm 35 now, but I was officially diagnosed 4 years ago. My PTSD is as a result of being raped when I was 20 (nearly 21). It's only now that I know more about PTSD, that I can see I had many symptoms before my diagnosis (hyper vigilance, always on edge, and very sensitive to other around me, also being really jumpy at any sudden movements).

I have to be quite honest, in that I don't understand what age has to do with it. I'm sure plenty of people here lived with symptoms before they had an official diagnosis. I don't think you can be too young to have a diagnosis of PTSD, if the trauma affects you, and you fit the diagnostic criteria, then age doesn't matter.