Clinical response to placebo (modified Unified Parkinson Disease Rating Scale score at baseline [mUPDRSBL] − mUPDRS score following placebo [mUPDRSPBO]), adjusted for mUPDRS baseline and age. Values are given as mean (SD). There was no significant main effect of group. Only the change in group C was significant. *P < .05. In group A, subjects were told that their chances of receiving active levodo