Mental trauma appears to have increased over the past century, with a few hundreds in WW1 experiencing shell shock or being executed for "cowardice", more SS in WW2, "post-Vietnam syndrome", and finally PTSD from 9/11, civil war in Rwanda etc.
Prior to 1900 eg: Boer war, Crusades I can't find much talk at all about these kind of mental tolls. Were we just more badass because the baseline for violence was much higher eg: Roman games/pubic executions?
There was a discussion about PTSD last week in which a historian brought up his work with Napoleon's soldiers being diagnosed with "nostalgia". It doesn't seem like we have a clear answer as to whether or not this classification provides an accurate analogue to PTSD like shell shock might, but it should lead you in the right direction.