For instance, during the civil war, revolutionary war, and even further back?
PTSD questions are popular and have been asked a lot so I'm just going to link the PTSD section of the sub's FAQ
There was a recent article about post-traumatic stress in ancient Mesopotamian warriors, specifically those of the Assyrians (1300-600 BC). Here is a link to the article:
The basic gist of the paper is that several ancient medical texts describe symptoms similar to what we diagnose as PTSD. One criticism of the article is that much of it is centered on establishing the brutality and trauma that "must have existed" rather than establishing the evidence. It starts off with a lot of circular reasoning. However, they do eventually cite some case studies of texts referring to PTSD-like symptoms. Interestingly, the ancient Mesopotamians refer to these symptoms as the effects of the ghosts of the enemies they killed.
Here are the threads from the FAQ section linked by /u/8BallTiger:
How did the soldiers of antiquity/medieval times deal with the inevitable PTSD type issues that come from brutal hand to hand combat? - 147 comments, over 1 year old.
More examples from all across time, with analysis and source criticism present in several of the comment threads.
Was PTSD any more, or any less, prevalent amongst ancient and medieval soldiers than todays soldiers? - 16 comments, over 2 months old.
This thread delves into a discussion of the merits and flaws of an often cited work on PTSD amongst pre-modern warriors.
Did Ancient peoples suffer from Post-Traumatic Stress Disorder or similar psychological issues? - 55 comments, over 2 years old.
There's a wealth of examples drawn up in this thread though not as much analysis.
Is there any information on Post-traumatic Stress in societies in which warfare was looked at in a more favorable light (e.g Sparta)? - 41 comments, over 2 years old.
The topmost comment draws examples from the thread above this, but down below there's a source brought in to analyze pre-modern combat which results in a debate both about such occurrences and the value of the source.
Are there any indications of combat PTSD in societies like the Spartans, Khan's or Alexander's armies? - 31 comments, over 1 year old.
This thread narrowly focuses on Roman soldiers and thus is able to do strong analysis of the available texts and evidence in a way not done in the threads above.
Is there evidence of PTSD in ancient warrior cultures? - 14 comments, over 1 year old.
A few more examples ancient examples as well as dealing with a book on the topic of PTSD.
Did men of the past suffer emotional trauma from war and killing? - 6 comments, less than 1 month old.
This thread goes deep into the source criticism and interpretation when making judgements of whether or not pre-modern peoples were experiencing what would be diagnosed as PTSD in the modern day.
Did soldiers in the middle ages get PTSD? If so, was it different then PTSD now? - 83 comments, over 2 years old.
There's some debate in this thread whether or not the circumstances that people lived in during the Middle Ages made them more resilient or not to PTSD.
Is there any mention in medieval books and records from those times of what we now call PTSD in knights, soldiers, warriors etc? - 9 comments, less than 1 month old.
There's one large quote given in this thread about how clergy specifically cited the psychological toll of combat as a reason against it.
How was PTSD (Post-Traumatic Stress Disorder) treated in the Middle Ages of Europe (or anywhere during 400A.D. to 1500A.D.)? How well documented are we upon the subject? - 26 comments, over 10 months old.
Despite the title, this thread focuses on Early Modern Europe and also deals with the difficulty of retroactively diagnosing people through their writings.
How common was PTSD in 18th and early 19th century armies? Particularly in Napoleon's armies - 4 comments, over 11 months old.
One commenter talks about a high level officer who may have experienced PTSD such that it impacted his decision making at a critical moment in a major battle.