After 12mos, unless someone is Schizophrenic (which studies have proven, for some reason, the placebo affect seems to INCREASE) the placebo-effect seeks it's OWN 'homeostasis'.
How they in fact measure that & come to this conclusion is unknown to me. However, the longer the trial the less they believe the placebo effect plays a role.
And, BEFORE YOU RETORT, I should ADD that if there is a Placebo affect ASSOCIATED WITH taking a pill (whether it provide some ACTUAL, MEASUREABLE relief or result) then the PERSON who is TAKING
the EFFECTIVE (presumably) MEDICATION is also getting the SAME!
So the normalization should be IN THE STATISTICAL DATA!! Keep that in mind!