There is more evidence to fight that PTSD in knights didn't exist. Including that many knights came from upper middle class and nobility. They would typically be raised from a young age, around seven or eight, learning the manners and skills a knight would use in his everyday life. With the goal of knighthood in mind, there is much evidence that through physically preparing one's self, the mind also would strengthen making it easier to handle the strains of war. However, during the First Crusade, in 1096 a bastard soldier, Thomas de Marle, an experienced fighter from his paternal struggles with his father back home, joined up with French and German crusaders. On his travels, to Jerusalem he fought bravely making a name for himself and the Chanson d'Antioche (Song of Antioch) would later tell his story including that he was the first knight to scale the wall. Once the soldiers scaled the walls, a massacre perused, motivated by years of hardship the knights experienced during their pilgrimage including: extreme climate (hot and cold), severe lack of supplies, and fighting in foreign hostile lands. To add to that, it's estimated 1 in 3 crusaders died on their way to Jerusalem. Professor Jay Rubenstein of the University of Oxford University of Tennessee, argues that the First Crusade was a different kind of warfare, unknown to the knights of Western Europe and that they weren't experienced to handle this style of fighting. He writes "The result was a new level of violence, leading to battles that in scale and character were truly apocalyptic...such battles would have been for the soldiers a transformative experience, and probably not a positive one. The levels of bloodshed and brutality were so far beyond ordinary warfare that the experience of it would have changed the warrior's sense of their own humanity. Around 1107, one writer, Baudry of Bourgueil, observed, 'Of the fear of the dead customarily felt by the living there was none, since they had grown used to the dead being everywhere next to them just as the living. The stench hardly bothered them, for it had become natural to know and see and even sleep amongst the dead without revulsion'." - /u/Evolutionary_Mishap