After combing through movie lists from IMDB to Reddit, I think I've created the most complete collection of horror movies that climb inside your skull and mess with your brains.
'Beginner's Guide: Psychological Horror'
'What Exactly Is a "Psychological" Horror Film?'
'Why We Crave Horror Movies' by Stephen King
'Common Themes in Psychological Thrillers'
'Psychological Horror in the Films of David Lynch'
2017-10-07: Added The Conjuring 3, The Nun, The Crooked Man, Dead Snow 1&2, The Exorcist (Season 2), The Grudge (Reboot), IT (1990), IT (2017), IT: Chapter 2, The First Omen (prequel), WolfCop and Another WolfCop. Films yet to be added (missing in database): Cubed (Cube 4), Beyond the Green Inferno, A Haunting at Silver Falls 2, The House on the Edge of the Park 2, JeruZalem 2, Lights Out 2, "Pumpkinhead", Strangeland: Desciple, Tremors 6, Tucker & Dale Vs. Evil 2