system
Given the following post, respond as if you're commenting on Reddit:
human
[Fallout] Can humans become "Nightkin" with blue-skin and mental illness from long-term overuse of stealth boys just like super mutants?

...Or is there something unique about mutants that makes them alone susceptible to the further transformation? Alternatively, is it possible that becoming a blue "Nightkin" simply takes longer than the lifespan of a regular human, considering how the mutant Nightkin are only visibly different from regular super mutants in New Vegas, set more than a century after that mutant population's debut?

I'd personally love if the "Nightkin" side-effects were implemented as a condition gained from using enough stealth boys in a future game, complete with additional schizophrenic dialogue options. It would probably be much simpler to program than the player being able to become a ghoul...
gpt
I think exposure to high concentrations of FEV making the genome more mutable is probably what causes Nightkin to develop the way they do. Humans would thus presumably not be affected under most circumstances.