Well, there are studies that examine the "healing power of prayer" in a medical setting. In triple-blind, randomized controlled trials they determined that prayer helped heal, had no impact, or made it worse. So... what you'd expect from something that doesn't do anything, I guess. But the study does outline the reasons that prayer might be beneficial, and why it may have been beneficial for those it benefited:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2802370/
But really, it has a place for those who thinks it should have a place. It's that simple. I have a plethora of health problems, and I see so many people around me in hospital waiting rooms clutching a rosary or a cross. If you're, say, Christian, then of course God will be an important part of your life when you combat a serious illness. As long as they're not neglecting legitimate medical treatment in favor of a prayer circle, then they can do whatever they want to feel at peace with themselves.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2802370/
But really, it has a place for those who thinks it should have a place. It's that simple. I have a plethora of health problems, and I see so many people around me in hospital waiting rooms clutching a rosary or a cross. If you're, say, Christian, then of course God will be an important part of your life when you combat a serious illness. As long as they're not neglecting legitimate medical treatment in favor of a prayer circle, then they can do whatever they want to feel at peace with themselves.