[tyleraland]

Ancient warfare: anxiety as one anticipates impending war, which may be known months or years in advance (armies were slow), and very bloody melee combat which probably left survivors with PTSD.

Pre-modern warfare: relatively few people lined up and shot each other to death from long distances. People on the front lines knew they were likely going to die.

Modern warfare (WWI and beyond): constant artillery fire inflicts chronic and acute shell shock [1].

[1] https://en.wikipedia.org/wiki/Shell_shock

[dbcurtis]

Except thar I recently read that some are thinking that PTSD is the result of concussion from being near explosions. PTSD may well be mechanically induced.

[DenisM]

It doesn't explain non-e plosives PTSD, such as procured by military drone operators.

http://www.salon.com/2015/03/06/a_chilling_new_post_traumati...

[specialist]

IIRC, actual combat hours have increased, a lot. Soldiers were doing front line combat duty for a few weeks during WWII, for months during Vietnam, for years during Iraq. That duty will scramble your brain, sooner or later. With longer combat duty, it's becomes ever more likely.