Nocebo Effect

The nocebo effect occurs when a patient's own expectations about a treatment cause the treatment to have a worse effect than it otherwise would, for instance experiencing an anticipated side effect of a medication even when the substance received is actually inert. More broadly, it describes falling ill simply by consciously or subconsciously anticipating a harmful event, and it is the mirror image of the placebo effect, in which expectation improves an outcome rather than worsening it. Both effects are presumed to be psychogenic but can produce measurable changes in the body, and a review of 31 studies on the nocebo effect reported a wide range of associated symptoms, including nausea, stomach pain, itching, bloating, depression, sleep problems, loss of appetite and severe hypotension.