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Abstract
Background: The Hawthorne effect on clinical studies in Parkinson’s disease has not been thoroughly investigated. Evidently the Hawthorne effect may have impact on study outcomes acting as a ‘pre-placebo’ effect in the recruitment phase, hence before inclusion.
Aim: The aim of this study was to discuss the Hawthorne effect in relation to clinical and self-reported outcome measures in a randomized clinical study in the recruitment phase and during the study.
Methods: Data from 97 participants with Parkinson’s disease treated with Transcranial Pulsed Electromagnetic Fields were applied, randomized to an active (n = 49) or a placebo treated group (n = 48). The participants received one home treatment session, for eight consecutive weeks. Outcome measures were the Unified Parkinson’s Disease Rating Scale, The 39-item Parkinson’s Disease Questionnaire and the WHO-5.
Results: No difference in treatment effect between the two groups was found pertaining the Unified Parkinson’s Disease Rating Scale. No difference in treatment effect between the two groups was found pertaining the 39-item Parkinson’s Disease Questionnaire, apart from the dimension mobility. No difference in treatment effect between the two groups was found pertaining the WHO-5 scale.
Conclusions: The Hawthorne effect may have caused a ‘pre-placebo’ effect on the outcome measures even before obtaining baseline outcomes measures. This study may have been particularly prone to a Hawthorne effect due to the intense contact with the participants before and during the study. Moreover, the Hawthorne effect should not be viewed upon as a single entity but rather as entities affecting outcome measures throughout the full study period.
Disclosure statement
The authors have no disclosures or conflicts of interest regarding this study. Impartial foundations sponsored this study.
Bo Mohr Morberg received financial support from the following the past year: Founding from Den A.P. Møllerske Støttefond (a Foundation), Grosserer L.F Foghts foundation and Odense University Hospital. Anne Sofie Malling received financial support from the following the past year: Founding from Den A.P. Møllerske Støttefond, Grosserer L.F Foghts foundation, Odense University Hospital and University of Southern Denmark. Bente Rona Jensen received financial support from the following the past year: Founding from Den A.P. Møllerske Støttefond, Grosserer L.F Foghts foundation and Odense University Hospital. Ole Gredal received financial support from the following the past year: Founding from Den A.P. Møllerske Støttefond, Grosserer L.F Foghts foundation and Odense University Hospital and from employment at The Danish Rehabilitation Centre for Neuromuscular Diseases. Per Bech received financial support from the following the past year: Founding from Den A.P. Møllerske Støttefond, Grosserer L.F Foghts foundation and Odense University Hospital and from employment at Psychiatric Research Unit, Psychiatric Centre North Zealand, University of Copenhagen. Lene Wermuth received financial support from the following the past year: Founding from Den A.P. Møllerske Støttefond, Grosserer L.F Foghts foundation and Odense University Hospital.