placebo

the greatest force in the human body is the natural drive of the body to heal itself, but that force is not independent of the belief system, which can translate expectations into physiologic change. Nothing is more wondrous than the fifteen billion neurons in the human brain than their ability to convert thoughts, hopes, ideas and attitudes into chemical substances. Everything begins therefore, with belief. What we believe is the most powerful option of all.
— Norman Cousins 1979 - Anatomy of an Illness