the accepted definition of a placebo effect is polluted by nihilist opinion.
For example the champions of nihilism at skepdic.com say:
Some believe the placebo effect is psychological, due to a belief in the treatment or to a subjective feeling of improvement.placebo effect
The keywords here are "the" and "effect"; there is no doubt the effect exists in this sentence.
..may have a medical effect based solely on the power of suggestion..Placebo - Wikipedia, the free encyclopedia
It works because I tell you it does, that is reason enough.
One more example?
people sometimes get better when they are taking a placebo.Placebo effect - Better Health Channel.
Now we can make up something far better as just a sugar pill. There is no need to fool the patient into thinking some medication works. The patient must learn he can heal himself with thoughts alone. This is proven fact! You can obtain super human power from eating a carrot if you can visualize doing it. If it sounds tremendously stupid to you then the carrot will go back to it's original quantum state. We have enough data to prove the carrot appears to you in the way you observe it - so it's not a static but a dynamic object.
As a note I should add that the placebo effect can also be triggered by other people as we are constantly subjected to the thoughts of others in more ways then we like to know. Distance is not an issue here. :-)