Bla ordlisten:
Nocebo effects are undesirable effects of an inactive treatment, such as drugs, devices, or procedures without active ingredients. Active treatments can also have nocebo effects. For this reason placebos are sometimes given to a comparison group in studies to distinguish between placebo effects and nocebo effects, and treatment effects beyond any placebo or nocebo effects.
If you feel that this definition hasn't helped you to understand the term, click on our monkey to let us know.