Lessebo effect
The lessebo effect is a phenomenon in psychology and medicine in which a person in a blinded clinical trial knows that they might receive placebo due to the existence of a placebo control group in the trial and this results in the person experiencing diminished placebo effects (positive expectations) and therapeutic improvement. It has been described in several contexts including clinical trials of treatment for depression, schizophrenia, Parkinson's disease, and rheumatoid arthritis.