title: Expectancy effect: impact of pill administration on cognitive performance in healthy seniors.
abstract: Expectancy or placebo effects on cognitive function have not been well studied. To determine the effect of taking pills on cognitive function, 40 participants were randomly assigned to a pill or no-pill condition. Healthy seniors who took a 2-week supply of methylcellulose pills, which they were told was an experimental cognitive enhancer, were compared to seniors not taking any pills. There were 2 primary outcome measures defined prior to the study-Consortium to Establish a Registry for Alzheimer's Disease (CERAD) Word List delayed recall and Stroop color word task time-as well as 7 other cognitive outcome measures. There was a significant effect of pill taking on the 2 primary outcome measures. There was also an effect of pill taking on choice reaction time and Word List immediate recall but not on the other 5 secondary cognitive outcome measures. In an exploratory analysis of potential predictors of the expectancy effect, perceived stress and self-efficacy but not personality traits interacted with the pill-taking effect on cognitive function. Further characterizing and understanding this observed expectancy effect is important to maximize cognitive health and improve clinical trial design.
authors.affiliation: Department of Neurology, Oregon Health & Science University, Portland, OR 97239, USA. oken@ohsu.edu
authors.forename: Barry S
authors.initials: BS
authors.lastname: Oken
authors.forename: Kristin
authors.initials: K
authors.lastname: Flegal
authors.forename: Daniel
authors.initials: D
authors.lastname: Zajdel
authors.forename: Shirley
authors.initials: S
authors.lastname: Kishiyama
authors.forename: Mitchell
authors.initials: M
authors.lastname: Haas
authors.forename: Dawn
authors.initials: D
authors.lastname: Peters
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002755:Choice Behavior / Q000187:drug effects; D003071:Cognition / Q000187:drug effects*; D004311:Double-Blind Method; D030141:Feedback, Psychological; D005260:Female; D005500:Follow-Up Studies; D015577:Geriatric Assessment; D006801:Humans; D008297:Male; D009042:Motivation / Q000502:physiology*; D009483:Neuropsychological Tests; D018697:Nootropic Agents / Q000494:pharmacology*; D017063:Outcome Assessment, Health Care; D015990:Placebo Effect; D028321:Plant Preparations / Q000494:pharmacology*; D011237:Predictive Value of Tests; D011930:Reaction Time / Q000187:drug effects; D027543:Salvia officinalis / Q000737:chemistry; D012649:Self Concept
chemical_list: D018697:Nootropic Agents; D028321:Plant Preparations