The placebo effect may underpin some perceived benefit from a host of inactive treatments. But can the effect occur in reverse? Could one be convinced that a given intervention is harmful, even if it is completely benign? The answer is yes – if one is sufficiently swayed to believe that something is detrimental, then by the same psychological mechanism one is inclined to display negative reactions to the inert agent. This inverted cousin of placebo is known as the nocebo effect, and it is arguably even more potent.
