Virtualy any spiritual excercise drains one of energy. It's much the same way physical excercise drains one of energy, just a different kind of energy. Both are physically detectable. As for the Old Hag Phenomenon, I posted about the distinction from SP here. I have experienced both, and they are different things.

Automatic writing is akin to using a ouija board; it's just another method of channeling. Hmm, that answer was kinda all over the place, but then so was the question, I guess.