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The Hawthorne Effect: a randomised, controlled trial.

Rob McCarney1, James Warner, Steve Iliffe

  • 1Department of Psychological Medicine, Imperial College London, UK. robmccarney@googlemail.com <robmccarney@googlemail.com>

BMC Medical Research Methodology
|July 5, 2007
PubMed
Summary
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Intensive follow-up in dementia trials improved cognitive function, suggesting the Hawthorne Effect impacts generalizability. Minimal follow-up unexpectedly improved quality of life for participants.

Area of Science:

  • Clinical research methodology
  • Geriatric medicine
  • Psychopharmacology

Background:

  • The Hawthorne Effect may impact clinical trial generalizability, particularly in dementia research.
  • Previous studies noted Hawthorne Effects in dementia trials but did not quantify them.
  • This study aimed to quantify the Hawthorne Effect by comparing follow-up intensities in a Ginkgo biloba trial.

Purpose of the Study:

  • To compare the impact of minimal versus intensive follow-up on outcomes in a placebo-controlled trial for mild-moderate dementia.
  • To assess the Hawthorne Effect's influence on cognitive function and quality of life.

Main Methods:

  • 176 participants in a dementia trial were randomized to minimal or intensive follow-up schedules.
  • Intensive follow-up included comprehensive assessments at multiple time points.

Related Experiment Videos

  • Minimal follow-up involved abbreviated baseline and a final full assessment.

    • Main Results:

    • Intensive follow-up significantly improved cognitive functioning (ADAS-Cog) compared to minimal follow-up (p=0.037).
    • Participant-rated quality of life (QOL-AD) improved more with minimal follow-up (p=0.032).
    • No significant difference was observed in carer-rated quality of life.

    Conclusions:

    • Intensive follow-up in dementia clinical trials can enhance cognitive outcomes.
    • The intensity of participant follow-up influences trial results, highlighting the Hawthorne Effect.
    • Findings suggest careful consideration of follow-up protocols in dementia research.