L'effet placebo dans les recherches
English
Share
Overview
Source : Laboratoires de Gary Lewandowski, Dave Strohmetz et Natalie Ciarocco — Université de Monmouth
Recherche clinique met l’accent sur l’efficacité des traitements pour traiter les troubles et les maladies. Un défi avec ce type de recherche est que les participants aient souvent préexistantes croyances au sujet du traitement, particulièrement les attentes que le traitement va fonctionner.
Bien qu’il a été pratiqué dans le monde entier pendant des siècles, l’yoga est un engouement relativement récent de remise en forme aux Etats-Unis avec un large éventail d’avantages présumés, y compris la croyance qu’il améliore sa créativité. Cependant, il n’est pas toujours clair si yoga crée effectivement des avantages, comme l’amélioration de la créativité, ou attentes du praticien yoga sont vraiment la cause.
Cette vidéo montre une conception de deux groupes qui permet de vérifier si une personne qui croit qu’il ou elle fait yoga (mais en réalité n’est pas) connaît des avantages similaires à une personne qui ne fait d’yoga. Plus précisément, cette étude examine s’il existe un effet placebo tel que simplement croire vous faites yoga bénéficie de créativité.
Études psychologiques utilisent souvent des tailles d’échantillon plus élevés que les études dans les autres sciences. Un grand nombre de participants permet de s’assurer que la population étudiée est mieux représentée et la marge d’erreur accompagnée d’étudier le comportement humain est suffisamment pris en compte. Participants plus, humains pour la recherche comme celui-ci sont souvent facilement accessibles et l’expérience est rapide et peu coûteuse à reproduire. Dans cette vidéo, nous démontrons cette expérience à l’aide d’un seul participant. Toutefois, tel que représenté dans les résultats, nous avons utilisé un total de 80 (40 pour chaque condition) aux participants de parvenir à des conclusions de l’expérience.
Procedure
Results
80 participants were used (40 per condition in a different instance of this study conducted by the researchers). This large number of participants helps to ensure that the results reflect accurate mean numbers. If this research were conducted using just one or two participants, it is likely that the results would have been much different and not reflective of the greater population. The numbers reported reflect the mean number of creative uses for a clothespin participants in each condition listed (Figure 2).
After collecting data from 80 people, a t-test was performed for independent means to compare the placebo (belief in yoga) condition against the stretching condition. This simple two-group experiment shows how researchers use a placebo condition to test whether participants’ mere belief in a treatment’s effectiveness can influence outcomes on creativity.
Figure 2: Average number of creative clothespin uses by condition.
Applications and Summary
The use of placebo conditions is particularly common in studies where researchers want to test a medication’s effectiveness.
For example, DelBello and colleagues2 conducted a study of over 300 adolescents diagnosed with major depressive disorder. Researchers randomly assigned participants to either wear a patch (the selegiline transdermal system [STS] or EMSAM®) or to wear a placebo for 12 weeks. Compared to baseline measurement taken at week 1, both the treatment and placebo groups experienced similar reductions on their depression scores. This study demonstrates that those who simply believed they were receiving the treatment (i.e., the placebo group) experienced the same level of positive outcomes as those who received the actual treatment.
Similarly, Del Re and colleagues3 conducted a meta-analysis of 47 alcohol pharmacotherapy studies. They found that placebo groups had significant improvement overall and that improvements were greater in more recent studies. Improvements were especially likely when the placebo was administered more frequently and when participants had more severe illnesses.
References
- Guilford, J.P. The Nature of Human Intelligence. New York: McGraw Hill (1967).
- DelBello, M. P., Hochadel, T. J., Portland, K., Azzaro, A. J., Katic, A., Khan, A., & Emslie, G. A double-blind, placebo-controlled study of selegiline transdermal system in depressed adolescents. Journal of Child and Adolescent Psychopharmacology. 24 (6), 311-317. doi:10.1089/cap.2013.0138 (2014).
- Del Re, A. C., Maisel, N., Blodgett, J. C., Wilbourne, P., & Finney, J. W. Placebo group improvement in trials of pharmacotherapies for alcohol use disorders: A multivariate meta-analysis examining change over time. Journal of Clinical Psychopharmacology. 33(5), 649-657. doi:10.1097/JCP.0b013e3182983e73 (2013).
Transcript
Placebos are widely included in clinical research and play an important role in therapeutic interventions. While clinical research relies on the efficacy of therapeutics for treating many disorders and illnesses, participants often have preexisting thoughts that can influence the outcome of drug trials. Such beliefs are referred to as placebo effects. The placebo effect points to the importance of perception and a psychological role in physical health. For example, the recent rise in the popularity of yoga as a fitness routine in Western countries has led to widespread beliefs regarding its benefits on health and wellness, including the idea that yoga enhances creativity. Through a unique experimental design, this video demonstrates how to design, perform, analyze, and interpret placebo responses. Here, the study examines whether a participant’s beliefs that yoga enhances creativity influences their creativity by listing alternative uses for a clothespin after stretching.
This placebo experiment incorporates a two-group design, a placebo and stretching group. In this case, the experiment is designed to highlight the placebo effect and should not be considered a control group, as it would be in other experiments. The two groups undergo the same series of stretching exercises. The placebo group is led to believe that they are going to engage in a series of yoga movements, whereas, the stretching group is led to believe that stretching is a critical component to personal fitness, with no mention of yoga. Note: the only difference is in the instructions given to the participant and no actual yoga is performed. After stretching, the participants are asked to list alternative uses for a clothespin. This dependent measure is interpreted as creativity. Participants who believe that doing Yoga leads to enhanced creativity should display a stronger placebo response than those who do not.
To setup the experiment, you will need: informed consent paperwork, copies of the initial research description and goals, a blank, lined piece of paper, writing pen, a clothespin, and copies of the final nature of the study for debriefing. To begin the experiment, meet the participant in the lab and explain the experimental guidelines. Guide all participants through the consent process, brief them with a description of the research on yoga and creativity, and discuss the overall plan for the session, including the potential risks and benefits. Assign this participant to the placebo yoga condition. Influence the participant that he or she is about to engage in a series of yoga movements. Remember that participants are not doing actual yoga movements, just stretching. Once the participant has been persuaded with the intent of yoga, direct him or her to do several “yoga” stretches and hold them for 1 min. Let the participant know that he or she can withdrawal at any time and ask for help if they experience discomfort. While the other participant is stretching, bring a different subject into the laboratory and assign them to the other experimental group, the stretching condition. After the participant has consented to the experiment, convey the message that the benefits of stretching are being tested. Now instruct the participant do several stretches and hold them for 1 min. Note that these are purposefully the same stretches as in the placebo condition. In a different room immediately after the stretching exercises, give participants a piece of paper with numbered lines and a pen. Ask the participant to list as many possible uses as you can think of in the next 3 min for a clothespin. Once the 3 min task is finished, ask the participant about their perception of yoga as it relates to physical and mental benefits including creativity and open-mindedness. At the conclusion of the experiment, debrief participants and explain why deception was necessary for the experiment.
The analysis of creativity after “yoga” stretching involves counting the number of ways participants listed to use clothespins. The data are then graphed by plotting the mean numbers for each condition to compare the placebo “belief in yoga” condition against the stretching condition. In this experiment, the placebo group listed more ways to creatively use clothespins than the stretching group.
Now that you have seen an experiment designed to uncover the extent of a placebo effect, let’s take a look at how researchers include placebo groups as important controls to study the effectiveness of medications. For example, in pharmacotherapy studies, subjects are unknowingly given a sugar pill—the placebo—and an active pill—the drug—and take them in random order. In many cases, medications are effective and produce beneficial effects on the measured outcome, as in this example where motor function was restored in patients with spinal cord injury after the administration of an anti-depressant drug compared to the placebo pill.
You’ve just watched JoVE’s introduction to placebos in research. Now you should have a good understanding of how to design and perform the experiment, as well as analyze results and apply the phenomenon. Thanks for watching!