Because i doubt the average person, when confronted with a walking corpse chewing on the remains of his or hers loved ones, would calmly headshot the zombie and move on.

After the apocalypse people will be used to the sight and threat of zombies, but by now months of living rough and fighting for survival might have unhinged a few people.

So i'd like to see a mechanic to reflect the stress and mental trauma that comes from living in the end times.

What do you guys think?

I like you idea, it sounds nice, I like the idea of their being a mechanic that displays how much a person might be able to stand seeing, a bit like sanity in cthulhu games.

I'd rather see a sanity system than a fear mechanic. Some people just aren't afraid, nulled to that stuff by various means. That kind of stops at shooting loved ones. Likely has to do with a stat.

For what I gather in different reviews and an interview with the author it does, after a fashion (mental stress). It also seem to works like the OP mentions. As the characters get used to the situations around them their mental armor get higher and less stuff stress them.

I guess it will be a waiting game now, for some form of preview, beta or the final copy. But either way inreckon a sanity mechanic would have to be almost compulsory, or fear ecpscecially later down the line with cthulhu or the wrath of the gods. I mean how much divine intervention and he'll spawns would you be able to wintess and then not need a white cushion wall.

I particularly loved the sanity system in the best game in the universe: Eternal Darkness (ok, maybe not of the universe)

It was basically whenever you are alone/outnumbered in the close proximity of of living dead (and other horrors in the game) you'd lose a tiny bit of sanity that you could only get back by not only killing the horrors, but spending an extra action to "finish it" and that would restore the very amount you lost, meaning you often didn't get your full sanity back unless you did very well.

There is a suggestion about making sanity test in the book on the bottom of page 45.

For my part I was thinking of occasional "willpower" test whenever the PC's are facing increasing threat levels for becoming surrounded or seeing many living being devoured before them, rather than having them get 2+ negative dice on every test they attempt to get out, as it can lead to tier 2 and 3 stress for simply getting out of there with the best possible improvisation on their part.

I was also thinking about adding a hidden "sanity" stat for each of my players and hint them of their mental states in the narration. I'll probably run a few games before I incorporate a full system of my own, but I definitely want a sanity system in my games.