Is there any documentation describing or dealing with veterans with possible ptsd in say the Middle Ages? Or even Ancient Rome or Greece? I can only imagine some of their large battles lent themselves to psychological trauma for their soldiers.
This thread answers your question quite nicely, and if it doesn't look into the writings of Geoffroi de Charny. He was a knight from the 14th century that describes what we believe to be PTSD in his Book of Chivalry.
/u/michaeljonesbird has a particularly good post https://www.reddit.com/r/AskHistorians/comments/357ocd/did_soldiers_and_knights_in_the_middle_ages/
There is an entire section of the FAQ devoted to premodern PTSD. Have a look at the threads there - my own answer covers Classical Greece, but there are also comments on Assyria, Rome, and the Vikings.
The overall answer is that there are texts and sources that we can interpret as examples of psychological trauma, but we can never claim with certainty that they provide evidence of PTSD. The disorder is medically defined and cannot be diagnosed without examining the patient firsthand. All historical accounts that are cited in this context fall very far short of the level of detail needed to say with confidence that peoples of the past suffered PTSD.