I have heard these stories,also but have experience with people I know having complete succcesses with some afflictions, over the years.
Religions were based on something, way back. Yogis have demonstrated the ability to grow and cure cancer by meditation. I understand this was done at a big cancer institute back in the 70's hippie years.
Half of the kids were told to think about little-bitty "Luke Skywalkers" (remember this was in the 70's) waving around his light-saber inside their body, killing the cancerous cells with his weapon. It turned out that the kids who were told to visualize that scenario improved their condition dramatically. The control group did not do as well.
I d>There is more than just a placebo effect to praying, chanting or any other