LostinDC, there are two scientific reasons cutting does alleviate emotional pain. 1) The neurotransmitters released in your brain when physical pain (aka: cutting) occurs cause you to feel "better" and/or "relieved" etc. almost immediately; thus creating its highly addictive quality. (similar to the "runner's high" effect) 2) The brain can only process & respond to one type of pain (ie physical vs emotional) at a time; thus why a 'new' physical pain stimulus would over-ride/numb existing emotional pain.

I learned this info through obtaining my degree, and began cutting almost immediately- you know that saying "curiously killed the cat"?
Anyway, like Trippin, I strongly encourage you to look for other coping strategies that work for you BEFORE beginning this one. Its indeed much like a cheap addictive drug; hard to quit no matter how much desire you have to do so.
Take care