I just watched À l'intérieur (Inside) and it wiped me out it was so relentless. I've only experienced this a few other times with Haute tension, The Descent, and Audition.

What are some other movies that achieve this same feeling? I'm watching Irreversible soon, I know that will be one.

I'll throw out another Noe (Irreversible) flick then - I Stand Alone. I wouldn't consider it physical horror like Inside but I think it qualifies as draining.

some people don't consider david lynch's INLAND EMPIRE to be horror but it has it's moment of creepy scenes and i'd say that it is "draining" emotionally.

The Thing. Isn't it the answer the every question?

Honestly, though, I have to agree with the films you listed. I might also add Frontier(s). (Surely someone here has heard of it? ) It's not a very original film, but it is a bit exhausting. Same goes for the final 20 min. of Audition, Battle Royale and Henry: Portrait of a Serial Killer (although that one just makes you feel more dirty than drained).

If you got drained from those films......Irreversible is going to ruin you

Jacob's Ladder?

Don't know if it counts as "horror"... but... "Se7en" left me exhausted...

battle royale really made me feel very drained last time i watched it. And to go into another film that isn't really horror, but "Requiem for a dream" did the same thing.

Again, not horror but Head-On was an emotionally draining film. The lead actress, Sibel Kekilli, turns in an absolutely fearless performance. She's certainly come a long way since her turn in "Hotel Fuck Myself Well" (a rough translation)

As previously mentioned Requiem for a Dream, although not a horror film, owns this thread.

Any of the Japanese "All Night Long" series.

The films are short, but by the end you'll feel completely empty.

Most of David Cronenberg's films have this effect on me.

A recent one for me is The Mist. By the time the end came I was so drawn in and then it happens and I was crushed.

I certainly wouldn't recommend that anyone watch it (without knowing something about it beforehand anyway), but Cannibal Holocaust left me feeling dirty, disgusted and exhausted. That was a once-in-a-lifetime viewing for me.

Saw III - Especially the brain surgery scene.