I took it for a few weeks when I was going thru some post-surgery funk earlier this year. It did help. I wasn't dancing in the daffodils or anything while I was taking it, but I did feel normal instead of in a funk. I did 1 pill 3x a day, I can't recall which brand. I got it at Walgreens, brown bottle w/ a yellow label. I don't recall any side effects or any problems when I stopped. I'd say its worth a shot. I didn't know about the BC prob, but I'm not on the pill so it doesn't matter. I went to the Dr while I was taking it for something else (I can't recall what) and she prescribed painkillers or antibiotics and I wasn't supposed to take the St John's wort with that, as it messed up the other medication. I really do think its safe, but watch whatever else is being taken as well and make sure there are no interactions. If your friend is really, deeply depressed, I don't know how much it will help, but like I said mine wasn't too bad, and it def helped, and quickly, too.
Nan
Edit - Now that I read Jaffas post about the dentist - it may be narcotic painkillers it doesn't mix with. I know the Dr said it can affect your breathing w/ mixed with whatever it was. And since Jaffas references surgery, I believe it was painkillers