Investigating Hope and Expectations in Open-Label Placebos

Study Overview
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Brief Summary
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Research has shown that placebo effects contribute substantially to clinical outcomes. Recent evidence suggests that placebos remain effective even if they are openly described as placebos (so-called Open-Label Placebos). In this study, the investigators examine hope and expectations as components of open-label placebos in an experimental study investigating pain..

Detailed Description
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A growing body of research has indicated that placebos contribute substantially to clinical outcomes. Yet, the implementation of deceptive placebos in clinical practice is incompatible with key principles of openness and patient autonomy. However, recent research suggests that placebos remain effective even if they openly described as placebos (so-called Open-Label Placebos (OLP)), hence questioning the necessity of deception in clinical trials. However, research identifying the specific mechanisms underlying OLP is lacking. Therefore, the current study aims to examine hope and expectations as components of OLP in pain. For this purpose, experimentally induced heat pain is examined. First, all participants receive heat pain stimuli and evaluate them. Next, participants are randomly assigned to one of four groups: (1) a traditional deceptive placebo (DP) group, which is told that they receive an effective analgesic cream, (2) an OLP group inducing hope among the participants that the placebo cream could help them tolerating painful stimuli (OLP hope), (3) and OLP group raising the expectation that the placebo cream will help participants tolerating heat pain (OLP expectation), (4) a control group receiving no cream. Finally, participants receive and evaluate heat pain again.

Official Title
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Hope and Expectations as Components of Open-Label Placebos: An Experimental Study Investigating Pain

Conditions
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Pain

Intervention / Treatment
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* Other: DP
* Other: OLP Hope
* Other: OLP Expectation
* Other: Placebo cream
* Other: Heat pain


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: sufficient German language knowledge at least 18 years old Exclusion Criteria: current mental disorder current medical disease studying psychology or medicine pregnancy or breastfeeding period intake of drugs severely visually impaired

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 80 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: Participants are assigned to one of four experimental groups in parallel for the duration of the study
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Deceptive Placebo (DP)<br>After pretreatment heat pain assessment, participants are informed that they are about to receive an effective analgesic cream. In fact, they receive a placebo cream. Next, the posttreatment pain assessment is conducted. | Other: DP<br>* Participants are informed that they are about to receive an effective analgesic cream. They are instructed to apply the cream using a cotton pad.<br>Other: Placebo cream<br>* The participants receive an inert placebo cream (standard basic cream with oil of thyme produced by a local pharmacy).<br>Other: Heat pain<br>* Participant receive heat pain stimuli using the suprathreshold method of the Thermo Sensory Analyser (TSA-II), a commonly used device to study pain sensation and analgesic effects.<br>|
| Experimental: OLP with Hope (OLP Hope)<br>After pretreatment heat pain assessment, participants are informed that they are about to receive an placebo cream. They are told that the cream has no active pharmacological ingredient. However, using verbal instructions, the investigator aims to induce hope among the participants that the cream could have a positive effect. Next, the posttreatment pain assessment is conducted. | Other: OLP Hope<br>* Participants are informed that they are about to receive an placebo cream. They are told that the cream has no active pharmacological ingredient. Therefore, participants are supposed to evaluate the subjective probability for a positive effect of the cream as rather low. However, using verbal instructions, the investigator aims to induce hope among the participants that the cream could have a positive effect for them because this placebo cream did have a positive among some former participants who were similar to the current participant. The emphasis of this similarity (regarding age and sex) aims to induce a feeling of connectedness to previous participants who reported positive effects of the placebo cream.<br>Other: Placebo cream<br>* The participants receive an inert placebo cream (standard basic cream with oil of thyme produced by a local pharmacy).<br>Other: Heat pain<br>* Participant receive heat pain stimuli using the suprathreshold method of the Thermo Sensory Analyser (TSA-II), a commonly used device to study pain sensation and analgesic effects.<br>|
| Experimental: OLP with Expectations (OLP Expectation)<br>After pretreatment heat pain assessment, participants are informed that they are about to receive an placebo cream. They are told that the cream has no active pharmacological ingredient. However, using verbal instructions, the investigator aims to raise expectations among the participants that the cream will have a positive effect. Next, the posttreatment pain assessment is conducted. | Other: OLP Expectation<br>* Participants are informed that they are about to receive an placebo cream. They are told that the cream has no active pharmacological ingredient. However, participants are told that placebos have been shown to contribute substantially to clinical outcomes such as pain intensity/unpleasantness. This positive effect of placebos is reasoned by explaining learning mechanisms such as classical conditioning. We anticipated that after hearing this instruction, participants would consider it to be likely that the placebo has a positive effect for them.<br>Other: Placebo cream<br>* The participants receive an inert placebo cream (standard basic cream with oil of thyme produced by a local pharmacy).<br>Other: Heat pain<br>* Participant receive heat pain stimuli using the suprathreshold method of the Thermo Sensory Analyser (TSA-II), a commonly used device to study pain sensation and analgesic effects.<br>|
| Experimental: Control<br>After pretreatment heat pain assessment, this group does not receive an intervention targeting pain sensation prior to the posttreatment pain assessment. | Other: Heat pain<br>* Participant receive heat pain stimuli using the suprathreshold method of the Thermo Sensory Analyser (TSA-II), a commonly used device to study pain sensation and analgesic effects.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in pain intensity scale | Change in subjective pain intensity assessed using a visual analogue scale (ranging from 0 to 100, with higher values reflecting more pain intensity) | Baseline and 45 minutes | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in pain unpleasantness scale | Change in subjective pain unpleasantness assessed using a visual analogue scale (ranging from 0 to 100, with higher values reflecting more pain unpleasantness) | Baseline and 45 minutes | 
| Change in physiological heat pain threshold | Change in the individual heat pain threshold (the point when the stimulus changes from being warm to being painful) | Baseline and 45 minutes | 
| Change in physiological heat pain tolerance | Change in the individual heat pain tolerance (the point when participants cannot stand the heat pain stimulus any longer) | Baseline and 45 minutes |