title: Warning about side effects can increase their occurrence: an experimental model using placebo treatment for sleep difficulty.
abstract: Patients in clinical practice and participants in clinical trials are warned about side effects that may result from their treatment. Such warnings could lead to placebo-induced side effects if they create an expectation of these effects. We used an experimental model to test this possibility. Undergraduates reporting sleep difficulty received placebo treatment disguised as a hypnotic for one week and were warned about either one or four bogus side effects. Placebo treatment significantly improved sleep difficulty relative to a no treatment control group, as indicated by self-report and by objective outcomes. At the end of the treatment week participants who had been warned about a single side effect showed better recall of this effect than those warned about four side effects. Most importantly, participants tended to report experiencing a side effect they had been warned about, with a trend towards a larger effect in participants warned about one side effect. This evidence for placebo-induced side effects may need to be considered when interpreting data on side effects from clinical trials.
authors.affiliation: School of Psychology, University of Sydney, Sydney, NSW, Australia. ben.colagiuri@sydney.edu.au
authors.forename: Ben
authors.initials: B
authors.lastname: Colagiuri
authors.forename: Kari
authors.initials: K
authors.lastname: McGuinness
authors.forename: Robert A
authors.initials: RA
authors.lastname: Boakes
authors.forename: Phyllis N
authors.initials: PN
authors.lastname: Butow
mesh_terms: D000293:Adolescent; D030881:Disclosure; D005260:Female; D006801:Humans; D007258:Informed Consent / Q000523:psychology*; D008297:Male; D015990:Placebo Effect; D035842:Research Subjects / Q000523:psychology; D012893:Sleep Wake Disorders / Q000188:drug therapy / Q000523:psychology*; D013334:Students; D055815:Young Adult