Indeed, but not every one of the reactions described idan, mattdeboard, or roqetman is attributable to a disorder. For example, freezing and trying to analyze the sound whenever an explosive noise occurs (or even ducking for cover) is not necessarily a pathological reaction - it could simply be a learned and throughly ingrained response. The patterns you learn in situations where your life depends on a trained behavior tend to be imprinted very deeply.

There are a couple of other things that need to go wrong until the diagnosis of PTSD is applicable. Sadly, this is not exactly made easier by the fact that people tend to have vastly different reactions and symptoms.