PTSD is one of those things that's been a lot longer than people think- IIRC one ancient chronicler mentions something along the lines of a greek (or macedonian I don't remember) hoplite who 'upon seeing his friend being killed next to him was struck blind'.
Many soldiers historically come back from wars effected in one way or another, but it of course was first widely bought to attention as 'Shell shock'- with the advent of modern war and constant shelling, it was like some of you up there have said, impossible to switch off, as death could come whistling from the sky at any moment.
Now in addition to this they also have to worry about drones coming to merc them at any moment.
There's going to be a lot of it on both sides, and it will probably be widely studied and documented, which is quite interesting if in a morbid way...and it's going to be a big part of rebuilding after the war. When people think of the costs of rebuilding it's usually in terms of material costs, not human.
Whilst I feel less sympathy for the invading Russians (for those with enough money or resources, simply buggering off to Georgia or bribery or something is an option), you know there are some mobiks dragged in from the rural districts who you know are going to suffer in the same way, but I don't think the 'Russia STRONK' mentality is going to lead to them getting much help- but I'm not russian and I've not really looked into the aftermath of their invasion of Afghanistan as a more modern example, so I could be talking out my ass.
This is KF though, so I don't really know if it's the right place to be worrying about human costs.