Probably, yes. There are also case studies from members of American Indian nations who fought in modern wars and, when returning home, participated in their nation’s traditional warrior rituals; this also seems to help.
It should also be mentioned that ancient warfare has a lot of important psychological differences to modern warfare. Most tactics entailed standing literally, physically, shoulder to shoulder with your comrades in common purpose. People instinctively feel safer in the company of other (friendly) people, which is conducive to traditional formation tactics but not conductive to modern dispersal tactics, where you need to stay a safe distance apart from the next guy so you aren’t both killed by the same grenade or landmine.
Speaking of grenades and landmines, ancient warfare was not as loud and concussive and cacophonous as modern warfare. Its hard to say for sure which is worse—much has been written about the primal human fear of cold, sharp steel—but the constant, deafening gunpowder and explosives of modern warfare are certainly very different. In the First World War, the term “shell shock” was coined, based on the theory that the repeated concussive impact of artillery shells landing nearby could cause some soldiers to experience not just psychological symptoms but also the neurological effects of repeated brain trauma. Later on, people assumed shell shock was just PTSD, but my understanding is that they might have been onto something about the traumatic brain injuries all along. On the other hand, I wouldn’t be surprised if people also got a lot of traumatic brain injuries fighting in a phalanx, too. But on the gripping hand, if you’re fighting in a phalanx, you can actually do something! You don’t have time to just sit around thinking about how you might die the way you would sheltering from a modern artillery bombardment. You’re not at the mercy of terrifying forces much bigger than you are, you’re facing off at close range against a bunch of guys fundamentally no different from you, with a bunch of weapons that are fundamentally no different from yours. Unless they have elephants and you’ve never seen an elephant before, but even they weren’t as scary as you’re probably imagining. When I say “elephant” you’re probably thinking of gigantic African elephants, but nobody ever managed to tame and ride into battle. Instead they used smaller elephants; they were bigger than horses and plenty scary but there were ways to deal with them.
If you were a citizen-soldier of a Greek city-state, the comrades you fought shoulder to shoulder with would be fellow members of your peacetime community. You’d probably live your entire life within the same group of people and if you fought, you’d fight alongside them. There seems to be a lot of value in veterans maintaining social bonds with each other. This is what groups like the VFW were for, except for the ancients, there wouldn’t really be a need to go out of your way to join the VFW because the actual, specific men you fought with would still be your peers in your normal social milieu.
Also, modern warfare probably entails a lot more sleep deprivation. Partly to cope with this, modern soldiers are much more dependent on various stimulants; amphetamines and are out of fashion but nicotine and caffeine are very popular.
Modern culture also has much stronger taboos against violence. In earlier times (and I’m talking about even the 20th century or so), fistfighting was a normal part of life, slaughtering animals for food was something many if not most normal people were accustomed to doing from time to time, and people weren’t as squeamish about this sort of thing. I’m not saying this is a better way to live, but if you take a 21st century kid who might have never even squished a bug and then get him to use 21st century technology to kill people and blow things up, that’s a really big leap. Not every culture has our universal violence taboo. I’ve even read that in some nomadic and tribal cultures, men engaged in warfare practically as sport. They didn’t go raiding their enemies out of some sense of duty or competition for resources; it’s just normal behavior in their culture and if anything they enjoy it. In a lot of modern western accounts, people have admitted complicated feelings of guilt for enjoying the thrills of battle. Not every culture has hangups about this sort of thing.
So all in all I would guess that modern wars push people much farther than ancient wars did. They are operating much farther away from the normal parameters human beings evolved for (which probably were extremely violent by modern standards), in alienated and atomized modern cultures that were designed to scale beyond traditional Dunbar-scale bonds of group identity, inside of a value system that categorically taboos the kind of violence inherent to warfare, using modern weapons that have significantly more violent effects, frequently outside of normal circadian rhythms and under the influence of high doses of stimulants.