A rather interesting article on how your body trains itself to respond to medicine:
http://mosaicscience.com/story/medicine-without-the-medicine-how-to-train-your-immune-system-placebo
Noteworthy in the study is how the mice died even when no poison was administered, the thought/association of dying was enough...
And there's this - the placebo effect is rising: http://www.nature.com/news/strong-placebo-response-thwarts-painkiller-trials-1.18511
Which raises some interesting questions about medicine in general. But I'll let you ask those on your own...