PTSD (as it is known for short) is a very common problem among many soldiers returning home from war. But war is no new thing in human history and we have seen much more carnage in a much larger scale in the past. Humans have not changed much over the years so I would imagine PTSD was also very common in the past. When was the first account of PTSD and what did it describe?
The earliest I can find is during WWI with "shell-shock" that soldiers went through. Are there any earlier accounts?
Something along the lines of PTSD was identified by the time of the American Civil War, when it was known as "soldier's heart."
Before that it wasn't conceptualized as a distinct psychological syndrome, but Shakespeare's Henry IV, Part I has a speech in which Lady Percy asks her soldier husband Hotspur what's wrong. Describing his symptoms, she hits the diagnostic criteria for PTSD with uncanny precision - insomnia, lack of interest in sex, withdrawal from others, zoning out, exaggerated startle reflex, nightmares about his experiences in war, etc.
Before that, Herodotus mentions an Athenian named Epizelus who experienced psychosomatic blindness after fighting in the Battle of Marathon. The battle took place in 490 BCE.