Nocebo effects on informed consent within medical and psychological settings: A scoping review

Warning research participants and patients about potential risks associated with participation/treatment is a fundamental part of consent. However, such risk warnings might cause negative expectations and subsequent nocebo effects (i.e., negative expectations cause negative outcomes) in participants. Because no existing review documents how past research has quantitatively examined nocebo effects–and negative expectations–arising from consent risk warnings, we conducted a pre-registered scoping review (N = 9). We identified several methodological issues across these studies, which in addition to mixed findings, limit conclusions about whether risk warnings cause nocebo effects.