For me, it was a major trigger for depression. In high school, moments after hearing about "the unpardonable sin", I had concluded that I had done it (as the thought of a sin is considered the same as physically committing it, according to the bible), and in my mind, perception of the statement constituted sin. And if not, the thoughts that followed it most certainly were.
At this point, I felt that I had been rejected by God. I was already (nearly) universally rejected at school and ignored at home. This now meant to me that I was rejected everywhere, which was quite devastating.
While I did eventually "get over it", it was through a logical analysis of the religions I had been exposed to, which definitely did not build any faith.
Though I cannot say I am an atheist either. As crazy as it sounds, I have seen proof of the devil, which in turn is proof of God (I'll do a write up about this some time). This alone is enough to say that I cannot be considered agnostic, though I have had a long-standing belief that most religions are merely man's interpretations thereof, all of them flawed, yet at the same time carry a universal truth of the existence of the unseen (though to what extent is debatable).
Now, my primary use for religion is social networking. I know that I will probably never be able to believe what they do, yet I have very limited options for interaction (as I live in a small town and have been unable to make any friends), and religion represents a consistant outlet, through the regular meetings that people have provided because of it.