In the blog In His Works, Eric Chua wrote about how easily drugs can take the place of relationships with other people. In Dr. David Eckman - What’s Good About Alcohol and Heroin, he quotes (I think) Eckman, author of Sex, Food and God:
As an example, on the Internet there is a Web site that talks about oxytocin; it is called the love drug. We no longer need God because all we have to do is inject oxytocin. The author of the article is dead serious. He maintains that belief in God produces oxytocin, the chemical of secure and caring relationships. So forget God – just get the chemical.
(He's not talking about Hug the Monkey, by the way. I always advocate getting your oxytocin the natural, organic way: hugs, sex, puppies, hanging out with friends.)
This post doesn't make it explicit, but it sounds like Eckman sees relationship with god as equivalent to relationship with another human. I'm pretty sure that those people who have a personal relationship with god -- or a higher power as they know it -- activate the same brain circuits when they pray, meditate, think about or otherwise connect with the higher power as they do when they connect with people they're intimate with -- and obtain the same oxytocin release.
I think the key is, for this to happen, you have to really feel and believe that this other being exists.