Horror Gaming - It's an aid not a crutch.

It has become a challenge among game designers to create the feeling of horror, stress, fear, etc in their games with actual mechanics. Which I do see a really good thing that leads to some wonderful creative systems. The Madness Meter from Unknown Armies is one of the first things that pops into my mind right next to the Mental Balance from Kult and lets not forget Sanity from Call of Cthulhu. They help players and the GM visualize just where they are along that downward slide from whatever horrible things are happening around them (or to them in some cases). However they do have one drawback from what I've experienced.

To often they can be used as the only indicator that it is a horror game.

Running a horror game the same way as you would any other dungeon crawl except that every now and then the player may loose a D6 of Sanity doesn't work out all to well. Your players just end up playing whack a mole with two forms of Hit Points instead of one. Even if there is a high mortality rate among the PC's that doesn't create a sense of horror except for having to take the time to roll up another character.

The mechanics are in there mainly to help the GM set the mood, they are essentially a GM aid of sorts. Use them as such right beside the rest of the bag of tricks that help make a game an actual horror game. You know like getting exquisitely descriptive about things that should send a chill down a persons spine. Covering all five of the senses, hell go and look up what something smells like so you can describe it better in the game. Go for that six sense even, that feeling of dread or tell them of a nagging thought in the back of the characters head. There are tons of tricks for horror games. Just don't get lazy and let a built in mechanic be the only one.