Y'know I've disputed the concept that All You Have To Do Is Beleeeeeeeeve," but there seems a strong element of truth to that in the placebo effect. It's a certain type of belief -- the type involved when an authority figure says "Take this, you'll feel better." I think it's something that we learn before we can even remember it, that mom or dad or another trusted person tells us "Take this, you'll feel better," and then -- we do! Usually it's 'real' medicine, like a pain reliever or cough syrup or antibiotics or whatever, but that experience stays with us and is strong enough to bring about the placebo effect later. Just a theory.