Placebo analgesia
Conditions
Interventions
Individual application or any combination of the placebo-related learning techniques verbal suggestion, observational learning and conditioning.
Sponsors
Leiden University
Eligibility
Inclusion criteria
Inclusion criteria: 1. healthy participants, aged 18-35 years, female or male, Dutch or English speaking.
Exclusion criteria
Exclusion criteria: 1. Presence of pain at the moment of testing (this includes chronic pain disorders, but also acute pain, meaning a NRS score of 1 or higher). 2. Use of prescription analgesics 24 hours prior to the day of testing (e.g., opioids, 5-HT receptor agonists.) 3. Use of over the counter analgesics within 12 hours before testing. 4. Presence of any severe physical or mental disabilities (e.g. cardiovascular disease, kidney disease, depression, autism). 5. Use of long-term medication for a physical or mental disability that might interfere with pain perception (e.g., anti-epileptics, antidepressants, opioids, cannabinoid oil). 6. Use of >2 alcoholic units within 12 hours before testing. 7. Use of any hard drugs (e.g. amphetamines) within 48 hours prior to testing. 8. Use of any soft drugs (e.g., marijuana) within 12 hours prior to testing. 9. Experience with previous research regarding placebo related learning techniques (verbal suggestion, conditioning, and social learning) 10. Pregnancy or currently breastfeeding 11. Injuries on the hands, wrists, or arms that will be used for testing and are at the location of the thermode or TENS electrode, at the time of participation. 12. Presence of a pace-maker or implantable cardioverter- defibrillator (ICD) 13. Minimal difference in pain score ranges (low-mid) after calibration of the heat pain, which makes application of different pain stimuli impossible.
Design outcomes
Primary
| Measure | Time frame |
|---|---|
| Placebo analgesia: The measurement for placebo analgesia will be the mean difference scores for pain intensity measured between the placebo and control trials for the initial three trial pairs (control - placebo) in the testing phase. The pain scores will be measured on an 11-point Numeric Rating Scale ranging from 0 to 10. The difference scores will be analyzed between groups as planned comparisons. | — |
Secondary
| Measure | Time frame |
|---|---|
| Extinction of placebo analgesia: Measuring extinction is performed by calculating the difference scores for pain intensity measured between the placebo and control trials for all trial pairs (control – placebo) in the testing phase. The course of these difference scores will then be analyzed to examine differences between conditions in the course of placebo analgesia. Individual characteristics: To assess potential mediators of the effects of different (combinations of) learning techniques on placebo analgesia, questions on pain expectation, state anxiety, and trust in the experimenter will be asked during the experimental procedures. To assess potential predictors of individual differences in placebo analgesia in response to the different (combinations of) learning techniques, validated questionnaires will be administered before the experimental procedures. Potential predictors include empathy, neuroticism, optimism, somatosensory amplification and worrying. Additionally to these personal characteristics, the influence of certain genes for their possible predicting value of placebo responsiveness is assessed by genotyping multiple Single Nucleotide Polymorphisms (SNP) previously associated with placebo analgesia. Potentially, additional genotypes will be tested when new research would indicate that these may be relevant for placebo responsiveness as well. | — |
Contacts
Public ContactHans van Lennep
Leiden University
Outcome results
None listed