This question comes up a lot! In fact in comes up so much that someone also asked it a few hours ago, haha.

The questions/answers are usually about ancient trauma, but the answers should be relevant for medieval warfare as well.

There was an excellent recent answer by u/Iphikrates about the ancient world:

Did ancient civilians get PTSD? What do we know of the psychological effects of war on noncombatants, and how they dealt with them?

Also by Iphikrates: Are there any examples of PTSD from early wars or time periods such as the Middle Ages? Especially in times where fighting and killing people was honorable and glorified?

And for some other previous answers there is this section in the FAQ.