I can't speak to whether the second person's reply is accurate, but it sounds just about right for the ancient world.
I mean, if you didn't understand PTSD or even mental health as a thing, and if you pretty much had to turn to the supernatural since nobody had scientific explanations for jack shit back then, it makes sense that your first instinct would be ghosts.
Boggles my mind to think of how scary and magical the world must have seemed before science took away so much of the mystery. I barely understand magnetism now (InsaneClownPosseMeme.jpeg). Of course everyone thought they were blessed rocks. Can you even fathom what you'd be thinking back then if your town, which had been around since recorded history, suddenly got annihilated by a flood? You'd be looking sideways at N'gallah for committing adultery for sure.
Think of how insanely brilliant and brave scientists had to be early on to go against everything that everyone else thought was obvious.
It's kind of interesting because in most cases the recommended remedies for various issues like that were bonkers. But sometimes they'd manage to arrive at a kind of correct answer through trial and error, and would just come up with an explanation for why it worked that made sense to them. Trepanation for example. It can release pressure on the brain in some cases and thus is a valid treatment for certain brain injuries or conditions, but ancient Egyptians who used it obviously didn't have access to something like an mri, so they figured that they were just letting evil spirits out.
This is such an interesting perspective on ghosts and their prevalence in history across the world. Reoccurring violent dreams or anxiety and fear in the middle of the night from PTSD would make sense.
Maybe not to you in our modern Western cultural context with a Christian definition of what a demon is. There's no telling how an ancient Sumerian would imagine the supernatural, other than that it's extremely unlikely to conform to the dogmas of any modern established religion.
I dunno, epileptic seizures were "demons", cancer would be a "demon", so ghosts of slain warriors could certainly be thought of a "demon" as well? You would have to ask that Sumerian Healer though: I wasn't there, so cannot speak for them:-).