Not being a religious person, I've always been skeptical of the value of prayer — at least of second-person prayer, where someone else prays for you. It seems that my skepticism is well-founded, if one believes in scientific studies: the New York Times reports that a medical study questions the power of prayer:
Prayers offered by strangers had no effect on the recovery of people who were undergoing heart surgery, a large and long-awaited study has found. And patients who knew they were being prayed for had a higher rate of post-operative complications like abnormal heart rhythms, perhaps because of the expectations the prayers created, the researchers suggested.
Of course, when it comes to supernatural issues, it's often hard to merge that with science. A coy God might just mess up the study on purpose, to keep us from knowing (or for some other reason we can't understand). So there's the general question of whether prayer lends itself to scientific study at all.
What's most interesting to me about this is the effect — at least, the apparent effect — of the awareness that one is being prayed for on one's health: the result that knowing that one is being prayed for actually seems to be deleterious to one's condition. I've always assumed, out of my own belief that if God exists she is not a micromanager, that such prayer is pointless but harmless, and that the good wishes of someone else certainly couldn't hurt. And now it seems that maybe it can hurt. I'm eager to see more study on that point.
The study also does not address first-person prayer, which I believe can help — not because of divine intervention, but because of the calming or healing effect that one's frame of mind and inner focus can have on oneself. I'd like to see that studied as well, though I think that's much harder to do in a scientific way (everyone will focus themselves differently, and some not at all, and if you tell people how to do it, to achieve any sort of consistency, then the mechanism itself biases the result at best, and probably ruins it altogether).
One thing that quite bothers me about the study is how much money was spent to obtain a result that's not likely to change anyone's mind nor behaviour. Believers will continue to pray; non-believers will continue not to. I suppose if the result had gone the other way, it might have prompted more prayer (but then we'd have to wonder whether that would "tip the odds" and change the result).
These results notwithstanding, if someone wishes me well... I thank them, and I accept, happily.