The developers liked the idea of dark corporate corruption and used the CIA Mind control program Project MKUltra, where the CIA among other things dosed unsuspecting citizens with LSD to see the effects of mind manipulation, as one of their inspirations.
Chris Walker, the hulking variant chasing Miles for most of the game maybe Outlast's most misunderstood character. If you can find his psychological profile in the Administration Block you'll find out the poor guy's lack of a nose or lips is because he was so anxious he ripped them off.
Want to go all Ash Williams on those Variants? In the courtyard level if you go into the first shed you see and look up with you're night vision you'll find the chalk outline of a chainsaw, a tip of the hat to Sam Raimi's Evil Dead series.