It's the "very likely before" part that intrigues me. After the Thirty Years War I pretty much lose interest in military history. Except for playing Panzer General!
Well, a quick search yields this teasing bit, albeit, not evidence per say (War of 1812)
Military Medicine | War of 1812 | PBS :
Capt. Eleazar Wood of Massachusetts, who saw action from Ohio to the Niagara border, observed:
What prospects of recovery had the wounded, dying for a gill of gin or a spoonful of vinegar? Neither were to be had!... The camp exhibited a very melancholy spectacle. It was by no means astonishing that the troops should be generally gloomy and low spirited, when we come to consider that they were principally men of family who were on a tour of duty only for a few days; that many were already dead, others dying constantly.
A further search regarding the American Revolution, yielded much older documentation;
PTSD and Shell Shock :
* For example, in the Epic of Gilgamesh, the earliest surviving major work of literature (dating back to 2100 B.C.), the main character Gilgamesh witnesses the death of his closest friend, Enkidu. Gilgamesh is tormented by the trauma of Enkidu’s death, experiencing recurrent and intrusive recollections and nightmares related to the event.
* Later, in a 440-B.C. account of the battle of Marathon, Greek historian Herodotus describes how an Athenian named Epizelus was suddenly stricken with blindness while in the heat of battle after seeing his comrade killed in combat. This blindness, brought on by fright and not a physical wound, persisted over many years.
* Other ancient works, such as those by Hippocrates, describe soldiers who experienced frightening battle dreams. And outside of Greco-Latin classics, similar recurrent nightmares also show up in Icelandic literature, such as
Gísli Súrsson Saga.
* In the Indian epic poem
Ramayana, likely composed around 2,500 years ago, the demon Marrich experiences PTSD-like symptoms, including hyper-arousal, reliving trauma, and avoidance behavior, after nearly being killed by an arrow. Marrich also gave up his natural duty of harassing monks and became a meditating recluse.
Nostalgia and Soldier’s Heart:
* In the last several hundred years, medical doctors have described a few PTSD-like illnesses, particularly in soldiers who experienced combat.
* In the late 1600s, Swiss physician Dr. Johannes Hofer coined the term “nostalgia” to describe Swiss soldiers who suffered from despair and homesickness, as well as classic PTSD symptoms like sleeplessness and anxiety. Around the same time, German, French and Spanish doctors described similar illnesses in their military patients.
* In 1761, Austrian physician Josef Leopold Auenbrugger wrote about nostalgia in trauma-stricken soldiers in his book
Inventum Novum. The soldiers, he reported, became listless and solitary, among other things, and efforts could do little to help them out of their torpor.
Etc.. The first two links I clicked. What I would look for, wouldn't be so much immediate observations, obviously, such as during or right after battle, yet long term personality changes noted by others.
It would not surprise me in the least to read about any military/warrior culture (Rome would be a good example) where the common man bearing the brunt of battle, very often pressed into service (perhaps 14th-18th Century Naval service), where examples could be found. From personal research, I did encounter texts discussing how Native American warriors and even chiefs after years of combat, eventually lost their taste for battle and dealt with other issues (melancholy-like), where they essentially 'retired,' relegating
themselves to simpler, less stressful sorts of things (painting/decoration and basket weaving/pot making noted).
K2
P.S.: For the record, I've played Panzer Blitz 
