[dkersten]

The placebo effect is a real thing that actually has benefits. In this particular case, even if smiling is purely placebo, all is well because a smile is free (of charge and of adverse side effects).

But in the case of many medicines, just because magic-miracle-pill-x "works for you" doesn't really mean its a good idea if it actually only works due to placebo: maybe its really expensive (for something that may as well be just sugar) or maybe there is actual medication that is much more effective or maybe its safety hasn't been fully studied as is the case with much alternative medicine.

In any case, Hitchens's razor applies:

    What can be asserted without evidence can be dismissed without evidence.