It's already established that there are records of PTSD occurring in medieval and ancient history, but were there any form of official, sanctioned treatment to handle people suffering from it in those time periods?

You may wish to read the Monday Method's thread by u/hillsonghoods on pre-modern PTSD, and the problems with discussing psychological phenomenon in the pre-modern world. Another answer by u/Antiquarianism goes into great detail about medieval stress, and there are also links in that thread to other, similarly worthy answers on the subject of PTSD in pre-modern times.