title: The Hawthorne Effect: a randomised, controlled trial.
abstract: BACKGROUND
  The 'Hawthorne Effect' may be an important factor affecting the generalisability of clinical research to routine practice, but has been little studied. Hawthorne Effects have been reported in previous clinical trials in dementia but to our knowledge, no attempt has been made to quantify them. Our aim was to compare minimal follow-up to intensive follow-up in participants in a placebo controlled trial of Ginkgo biloba for treating mild-moderate dementia.
  
  
  METHODS
  Participants in a dementia trial were randomised to intensive follow-up (with comprehensive assessment visits at baseline and two, four and six months post randomisation) or minimal follow-up (with an abbreviated assessment at baseline and a full assessment at six months). Our primary outcomes were cognitive functioning (ADAS-Cog) and participant and carer-rated quality of life (QOL-AD).
  
  
  RESULTS
  We recruited 176 participants, mainly through general practices. The main analysis was based on Intention to treat (ITT), with available data. In the ANCOVA model with baseline score as a co-variate, follow-up group had a significant effect on outcome at six months on the ADAS-Cog score (n = 140; mean difference = -2.018; 95%CI -3.914, -0.121; p = 0.037 favouring the intensive follow-up group), and on participant-rated quality of life score (n = 142; mean difference = -1.382; 95%CI -2.642, -0.122; p = 0.032 favouring minimal follow-up group). There was no significant difference on carer quality of life.
  
  
  CONCLUSIONS
  We found that more intensive follow-up of individuals in a placebo-controlled clinical trial of Ginkgo biloba for treating mild-moderate dementia resulted in a better outcome than minimal follow-up, as measured by their cognitive functioning.
  
  
  BACKGROUND
  Current controlled trials: ISRCTN45577048.
authors.affiliation: Department of Psychological Medicine, Imperial College London, UK. robmccarney@googlemail.com <robmccarney@googlemail.com>
authors.forename: Rob
authors.initials: R
authors.lastname: McCarney
authors.forename: James
authors.initials: J
authors.lastname: Warner
authors.forename: Steve
authors.initials: S
authors.lastname: Iliffe
authors.forename: Robbert
authors.initials: R
authors.lastname: van Haselen
authors.forename: Mark
authors.initials: M
authors.lastname: Griffin
authors.forename: Peter
authors.initials: P
authors.lastname: Fisher
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017028:Caregivers; D003071:Cognition / Q000187:drug effects; D016001:Confidence Intervals; D003704:Dementia / Q000188:drug therapy* / Q000453:epidemiology / Q000208:ethnology; D004311:Double-Blind Method; D015987:Effect Modifier, Epidemiologic; D005194:Family Practice; D005260:Female; D020441:Ginkgo biloba; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D008517:Phytotherapy; D010919:Placebos; D010936:Plant Extracts / Q000627:therapeutic use*; D011788:Quality of Life; D011795:Surveys and Questionnaires
chemical_list: D010919:Placebos; D010936:Plant Extracts