I think the mechanism comes from when a civilized person gets so used to violence and tragedy that they 'Does'nt really care about anything anymore' they get alcohol dependant. Dwarves have that already but you'll see if you mod then raws and run a human fort.
Makes sense to me, but I can see it being a placeholder, since some other needs on place don't make sense as coping mechanism for psychological trauma. Nobody is like 'Wow ever since Kogan came back fron the war where he slaughtered all those people and watched his comrades die and was horribly injured and nearly killed, he sure does admire artwork alot.'
I suppose everyone is different, some people get really religious or bury themselves in work but alcohol is a more natural solution.
Ethonol is natural? I'm pretty sure the 'natural' solution is PTSD, which generally involves sleeplessness, nightmares, depression, anxiety, anger, and a heightened propensity to suicide. Not trying to be combative, just wanting to make the point that alcohol dependency is not the obvious choice, just the most normative one.
Well, to his defense, PTSD is a modern mental illness. While it did happened and there are historical records of soldiers that shown signs of combat fatigue, it was excedingly rare in ancient times. This is due for the evolutionary reason behind combat fatigue, which is a corruption of our learning ability.
Long story short, if you are a gazelle see your grandmother surviving a tiger attack, you will learn from what you see and instinctively mimic what she did in the event you are under a tiger attack later. If you're a knight and manage to block an axe coming your way, you'll repeat the pattern that allowed you to survive next time someone tries to axe you
If instead, you're put in a trench under constant shelling, have no way of predicting how death will come and witness your tribemembers die without being able to give rhyme or reason of it, you will associate the constant shelling to immediate danger against which you cannot prepare, and will freak out next time a kid lights a firework in the vicinity.
In the other hand, studies show that a lot of animals have an ethanol addiction. Some bees, for exemple, can litterally get drunk on the pollen of some flowers (and are killed off by other bees when they come home late)