PTSD is a natural response to danger. From an evolutionary perspective, it's exactly the response you want to have when your life is in danger: you want to be vigilant, you want to react to strange noises, you want to sleep lightly and wake easily, you want to have flashbacks that remind you of the danger. It's almost unavoidable in the short term and mostly self-correcting in the long term.
The American military now has the highest PTSD rate in its history - and probably in the world. PTSD claims to the Veterans Administration have reportedly risen 60% to 150,000 a year. Anthropological research from around the world shows that recovery from war is heavily influenced by the society one returns to, and there are societies that make that process relatively easy.
Israel is arguably the only modern country that retains a sufficient sense of community to mitigate the effects of combat on a mass scale. Despite decades of intermittent war, the Israel Defense Forces have a PTSD rate as low as 1%.
Two of the foremost reasons have to do with national military service and the proximity of the combat - the war is virtually on their doorstep. "Being in the military is something that most people have done," I was told by Dr. Arieh Shalev, who has devoted the last 20 years to studying PTSD. "Those who come back from combat are re-integrated into a society where those experiences are very well understood." (Vanity Fair)