A completely overlooked area of possibility is the influence of lead from weapon use. Lead is known to cause reactions that are very similar to PTSD with or without the experience of war. In fact, a known side effect of lead contamination is rage which can manifest in many ways that resemble PTSD.
If you consider that the military still uses mercury in dentistry, still feeds soldiers food contaminated with GMO poisons and pesticides and gives little support in the area of mental health, it seems reasonable that the combination of these elements would offer symptoms that strongly mimic what is known as PTSD.
An interesting and practical study would be to test soldiers with PTSD for mercury and lead levels. It seems a very basic first step.