Does the Understanding of Placebo Mechanisms Compensate for the Loss of Efficacy Associated With Open Label Placebo

Study Overview
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Brief Summary
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The investigators are investigating whether, when given detailed information about underlying placebo mechanisms and pain, subjects will have a response similar to that of those subjected to a procedure in which they receive a conventional placebo treatment (associated with deception). STUDY DESIGN: This is a non-inferior parallel, controlled and randomized, single blind trial. POPULATION: The investigators will include in the study 126 subjects without known pathology. Participants will then be divided into 2 groups on a randomized basis. METHODOLOGY: Each subject will undergo three sessions of Cold Pressure Test (CPT), a cold pain stimulation method: calibration, condition of interest (conventional placebo or educated placebo) and control. The investigators' main judgment criterion is be the difference in pain intensity experienced on the visual analog scale between the CPT control and the CPT under the condition of interest. This study will allow the investigators to rule on the non-inferiority of an educated open label placebo compared to a conventional placebo in the context of an acute painful stimulation.

Official Title
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Does the Subject's Understanding of Underlying Placebo Mechanisms Compensate for the Loss of Efficacy Associated With the Disclosure of the Use of a Placebo

Conditions
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Acute Pain

Intervention / Treatment
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* Other: Educational movie on placebo mechanisms
* Other: Informative movie on hand washing


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Person affiliated to Social Security Informed consent, written and signed by the subject. Exclusion Criteria: Persons referred to in Articles L1121-5 to L1121-8 of the Public Health Code (CSP), which corresponds to all protected persons: pregnant women, parturient women, nursing mothers, persons deprived of their liberty by judicial or administrative decision, persons subject to a legal protection measure, cannot be included in clinical trials. Persons with a pathology against indicating the use of CPT experimentally induced pain : Any pathologies affecting the venous, arterial or lymphatic system Diabetes Cardiac disorders Asthma Frostbite Epilepsy Arthritis Lupus erythematosus Allergy to Cremafluid® cream Person with concomitant treatment that modifies sensitivity to pain, chronic or acute at the time of the experiment, such as analgesics, psychotropic drugs or anti-inflammatories.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 40 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: 2 groups : Educated open label placebo And Conventional placebo Each of the subjects will undergo the Cold Pressure text procedure under the condition of interest and a control.
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Educated open label placebo<br>These subjects will undergo all the same procedures as in the control group. But before the placebo CTP, they will watch a short movie explaining placebo mechanisms. While applying the placebo cream, they will be told that the cream is inert (placebo), efficient to decrease pain caused by cold and the mechanisms seen in the movie will take place. | Other: Educational movie on placebo mechanisms<br>* Educational movie on placebo mechanisms : animated video, duration : 12 minutes. It will be followed by the CPTs : experimentally induced pain by keeping the non dominant hand in cold water (1° Celsius) for a limited time. The duration of immersion is personal and calibrated to be around to ensure that the intensity of pain will be homogeneous (around 7/10 on the visual analogue scale with no treatment)<br>* Other names: Cold Pressure Test (CPT);|
| Placebo Comparator: Conventional placebo<br>These subjects will watch a video on hand washing. While applying the placebo cream, they will be told that this cream is effective to decreased pain caused by cold. | Other: Informative movie on hand washing<br>* Animated video, duration : 11 minutes. It will be followed by the CPTs : experimentally induced pain by keeping the non dominant hand in cold water (1° Celsius) for a limited time. The duration of immersion is personal and calibrated to be around to ensure that the intensity of pain will be homogeneous (around 7/10 on the visual analogue scale with no treatment).<br>* Other names: Cold Pressure Test (CPT);|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Pain intensity: Visual Analogue Scale (VAS) | Evaluated with a Visual Analogue Scale (VAS) from 0 to 100 mm, with a non inferiority margin at 10 mm and a standard deviation at 22 mm. | At the end of the CPT procedure, within 30 seconds after the removal of the hand from the CPT cold water tank. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Anxiety respiratory frequency change | Evaluated thanks to the respiratory frequency collect with a PneumoTrace belt through LabChart software. | During the CPT procedure | 
| Anxiety blood pressure change | Evaluated thanks to the automatic blood pressure monitor (both systolic/diastolic blood pressure, heart rate) | During the CPT procedure | 
| Knowledge of placebo's mechanisms | Evaluated with a questionnaire made for this study with 17 questions about placebo mechanisms. | At the beginning and end of the CPT procedures | 
| Perception of the investigator | The perception of the investigator will be evaluated by a visual analogue scale perception of the investigator. | At the end of the study, when all CPT procedures have been carried out, within 10 minutes after the last immersion | 
| The Perceived Awareness of the Research Hypothesis Scale questionnaire | Perception of the research hypothesis with the Rubin Questionnaire. Perceived Awareness of the Research Hypothesis  (PARH) wich is a scale of 4-item quantitative self-report method for measuring the potential influence of demand characteristics in research situations | At the end of the study, when all CPT procedures have been carried out, within 10 minutes after the last immersion | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Placebo, Experimental pain