You know, it shouldn’t exist. Human history and prehistory is crammed with all kind of mayhem and trauma: infant mortality, infanticide, genocidal fights with neighboring tribes. You routinely lost family and routinely killed enemies. Childbirth hurts a lot. What’s the adaptive strategy, in all of these situations? ? Get over it.
Although you can find academic papers talking about PTSD in the ancient world, they’re bullshit: people coming out of the Legions after putting in their 25 were not famous for screaming in their sleep. Neither were veterans of the American Civil War: nobody worried whether veterans like Benjamin Harrison or Garfield were damaged goods. But although it was the bloodiest war in American history it was mainly a rifle war, not an artillery war. You rarely got your brain thumped.
But in WWI, we heard a lot about ‘shell shock’. Later, in WWII, ‘combat fatigue’ or ‘battle neurosis’. Artillery wars. I would guess that what actually happened was a combination of people finding a way to avoid getting killed, and brain damage due to nearby explosions. After experience in Iraq and Afghanistan, plus football and boxing, people are thinking seriously about those explosions as a cause of PTSD.
Psychology in the 20th century looked for social/environmental causes of mental problems – toilet training, ‘refrigerator mothers’, ‘absent father/overprotective mother’, ‘double binds’. And of other social problems: school could make you smart or dumb, kids were ‘depraved because they were deprived’, blah blah.
As far as I can tell they were entirely wrong. Genetics and physical trauma ( which includes iodine shortages). No real sign that they were right about those other problems either: certainly interesting that the programs designed to ameliorate those problems, based on the standard environmental assumptions, never, ever work.