Good Psychological Thrillers?

Check out The Chaser

Also, if you liked Se7en, try Fincher's other flick Zodiac

Requiem for a Dream, not a thriller though.

the machinist, maybe?
http://www.imdb.com/title/tt0361862/

Usual Suspects, not psychological but good

try Poughkeepsie tapes

or Mientras duermes

or The skin i live in

or Cold fish

or 8MM

or Tesis

or Kyua

or Los sin nombre

or Audition

or others i guess :)

Watch the "Identity", or "1408". They are good movies.

Prisoners, you need atleast 2 times to watch it to understand it. Some parts didnt make sense at first time watching it, but 2nd time watching it made things more clearer.

Memento, Donnie Darko, Twelve Monkeys, The Machinist, Arlington Road, Moon, Buried, Misery, Inception, The Big Lebowski, Looper, 127 Hours, The Game, Sin City, The Prestige, Gone Baby Gone, ...
*I could write even more, but I think I was getting away from the psychological thrillers so I stopped hah

You will enjoy this movie

advise you to watch Mulholland Drive

The Cell
Clicky

The Shining? That's my go to movie for a good psychological thriller (Though Kubrick's other films like A Clockwork Orange and even 2001: A Space Odyssey could work). Also, as suggested above, 1408 and Alfred Hitchcock's Psycho are pretty good, as well as pretty much just about all of Christopher Nolan's films that aren't about superheroes.

Monster if Anime series is an option

Not really sure if it would count but I watched Falling Down last night. That was... well... interesting. Had some funny scenes but a lot of scenes that made you feel pretty uncomfortable. I've got lots of mixed opinions on this one, it's worth giving it a shot.