  in medicine, a nocebo (latin for "i shall harm") is an inert substance that creates harmful effects in a patient. the nocebo effect is the adverse reaction experienced by a patient who receives a nocebo. conversely, a placebo is an inert substance that creates either a beneficial response or no response in a patient. the phenomenon by which a placebo creates a beneficial response is called the placebo effect. in contrast to the placebo effect, the nocebo effect is relatively obscure. both nocebo and placebo effects are psychogenic. rather than being caused by a biologically active component of the placebo, these reactions result from a patient's expectations and perceptions of how the substance will affect him or her. though they originate from psychological sources, nocebo effects can be either psychological or physiological. ==etymology== the term nocebo (latin nocÄbÅ, "i shall harm", from noceÅ, "i harm")  was coined by walter kennedy in 1961 to denote the counterpart of one of the more recent applications of the term placebo (latin placÄbÅ, "i shall please", from placeÅ, "i please");  a placebo being a drug that produced a beneficial, healthful, pleasant, or desirable effect as a result of the subject's beliefs and expectations. ==description== w.r. houston may have been the first to speak of a doctor's deliberate application of harmful "placebo" procedures, as distinct from the other, harmless sort of "placebo" procedures a doctor might apply and whose "usefulness was in direct proportion to the faith that the doctor had and the faith that he was able to inspire in his patients." houston (1938, p.&nbsp;1418) wrote: {{quote|... [and while the efficacy of the placebo procedure] is believed in by the doctor, [the placebo procedure itself] is no longer harmless but harmful, sometimes very dangerous. it would seem peculiarly contradictory to speak of the painful and dangerous placebo, ye
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