So...essentially, lore consequences.
Given that if you look hard enough, there are stories about Iraq/Afghanistan veterans that find it hard to get back into civilian society due to injuries/PTSD/etc.--some commit suicide (quite a few, actually), and of those that do manage to live on that have seen some real stuff, a lot of them have PTSD.
Given the background for some champs in LoL, how are they, well, *champs*, and not sleep-deprived-by-way-of-nightmares mental trainwrecks?
Here are a couple of--but nowhere near an exhaustive collection of examples:
Riven: poster girl for this, seemingly comes closest to all the champs for actually not just shrugging off seeing all her friends (and foes) just gassed and being the sole survivor. In Confessions of a Broken Blade, she even developed amnesia because the events hit her that hard--but *after* that story? The Riven in-game is, what...6 years after that event? It seems she's the one that most heavily displays the consequences of it, though if her redeemed skin is any indication, she overcomes PTSD. How?
Irelia: family slaughtered at 14, spends the next 3 years fighting in a war, slaughters Swain's veterans and the guard of the general that killed her family, and said general himself--all at 17. The only consequences she displays is that she throws out a few more zingers here and there in her quotes. How is she not a complete mental train-wreck by this point?
Sejuani: considering she's always been raised in brutality, how is she still able to essentially be a female Genghis Khan, when she's led from the front for as long as she has, and then the run in with mutated Volibear, how have her faculties not slipped?
Is there some sort of special drug on Runeterra that keeps people that have seen a whole bunch of blood and horror from falling off the rails? How are some of these champs not just able to function, but fight with the best of them?