Also a psychologist here. This is a great question. Within my field, there definitely has been some theorizing that war-related PTSD is moderated by whether the conflict is considered to be just/glorious or unjust/immoral by society. I'll post more about this later and will try to dig up some research.
In the meantime, here are past threads that contain some great answers:
https://www.reddit.com/r/AskHistorians/comments/4bw9fd/ptsd_in_ancient_up_to_medieval_age/
https://www.reddit.com/r/AskHistorians/comments/1cpusf/is_there_evidence_of_ptsd_in_ancient_warrior/
https://www.reddit.com/r/AskHistorians/comments/tk3nl/did_ancient_peoples_suffer_from_posttraumatic/
https://www.reddit.com/r/AskHistorians/comments/1j6ssm/are_there_any_indications_of_combat_ptsd_in/
There are many others if you don't find what you're looking for.
While on the topic, if such records exist who were mainly affected by PTSD ? Was it noticeable in war oriented cultures like vikings ? or war oriented classes like say knight or samurais ? or was it mainly foot soldiers who were affected by it ?
There's a good answer to a similar question by u/sapere_avde here: https://www.reddit.com/r/AskHistorians/comments/1j6ssm/are_there_any_indications_of_combat_ptsd_in/cbbvfib
I can provide some insight into the military community of Plantagenet England from 1300 to 1421. I , of course, have a limited purview in this area. My sources for this will be Jean Froissart's Chronicles (he exaggerates, but I refuse to stop loving him as a source), Jean Le Bel's True Chronicles, The Chaplain's account of Agincourt, aswell as John Keegan's ever-faithful book 'Face of Battle', Christopher Allemand's Henry V, and the truly astounding compendium put together by Adrian Bell, Anne Curry, Andy King, and David Simpkin titled The Soldier In Later Medieval England.
Fuck, that's a lot of capital letters.
I feel an answer based upon these sources can be discerned, and I didn't find an answer from this particular viewpoint in /u/Rain12913's answer. Furthermore, I encourage said user to correct any inaccuracies I use in the field of psychology, as that is not my area of expertise.
To the meat.
Soldiers, warriors, the military class, probably had developed a great deal of desensitisation to violence from an early age that rendered physical combat less of a traumatic experience. Both Le Bel and Froissart mention accounts of every day violence, and many of the soldiers who thought at Crecy in 1346 had prior experience in major campaigns. However, the implication that medieval combatants coped 'better' with the trauma is up in the air.
Questions arise. Were they recorded? Were their chibbering wrecks at Agincourt and Patay, men reduced to nothing but PTSD? Did medieval kings show symptoms of the illness after vicious battles? For example, one popular theory by my old professor was that Marshal Ney showed clear signs of PTSD at Waterloo, but we cannot ever be sure. Furthermore, if we assume that the amount of combatants showing clear symptoms of PTSD is accurately reflected by the sources (which is by no means certain), then we must take into account that warfare in the medieval world was very different than it is today. Modern combatants often experience contact at distances of 500 yards and over, well beyond the effective range of a Mongol bow or a crossbow. They often experience intermittent enemy action for days at a time; seeing the Battle of Now Zad in Afghanistan. In contrast, even skirmishing and raiding would take up very little of a medieval combatant's time. Bannockburn and Towton were considered very extensive battles, with the former stretching intermittently two days and the latter consisting of combat for -TEN HOURS-. I believe this would have a significant degree upon the actual intensity and longevity of PTSD symptoms. Combining this with a sort of...vaccination against this horrendous violence with a life in which violence was, if not common place, more prevalent than today, and it might go some way to answering your question.
In terms of glory? I feel war was not quite so glorified in this period. The chivalric ideal was a huge overarching theme, yes, but John Barnis in 'War in Medieval English Society' argues for a more...practical outlook favoured by the English.
I'll summarise, but he basically says the English went to war to get fucking rich; chivalry was their manner of etiquette. It was how you popularised your legend, it was how you earned respect from your peers, but it was only one of several reasons to go to war. So, while I see your point, I feel that warfare wasn't quite so glorified as the chronicles lead on. Especially by the post-Bretagne period of 1360 onwards, the Hundred Years War achieved a low opinion in English society.
Yet instances of PTSD do not crop up in this period; perhaps because the English were losing and thereby less was written of it.
I don't know. I'll look anyone in the eye and say it. But my current idea is that PTSD was one of two things; either it simply wasn't recorded by chroniclers (I think this is very likely), or a combination of intermittent warfare and desensitisation meant that fewer individuals showed significant symptoms.
I hope this helps :)
Another previous thread on a very similar question, which has some helpful information: https://www.reddit.com/r/AskHistorians/comments/1les1j/how_did_the_soldiers_of_antiquitymedieval_times/