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Moderators of nocebo effects in controlled experiments: A multi-level meta-analysis.
Madeline V Stein1, Monika Heller2, Natasha Hughes3
1Department of Psychology, Institute of Psychology, Psychiatry, and Neuroscience, King's College London, London, UK.
Neuroscience and Biobehavioral Reviews
|February 6, 2025
Summary
Nocebo effects, where contextual cues worsen symptoms, are moderately influenced by suggestion type and administration mode. Technological devices, sham stimulation, and conditioning induce larger nocebo effects than verbal suggestion or social observation.
Area of Science:
- Psychology
- Neuroscience
- Medical Research
Background:
- Nocebo effects are a complex phenomenon where contextual cues, not active treatments, trigger or worsen symptoms.
- Established methods for inducing nocebo effects include suggestion, conditioning, and social observation.
- The differential impact of suggestion types and administration modes on nocebo effects across symptom domains is not well understood.
Purpose of the Study:
- To quantitatively synthesize research on factors moderating nocebo effects in controlled experiments.
- To investigate how suggestion type and administration mode influence nocebo effect magnitude.
- To identify specific methods associated with larger nocebo effects.
Main Methods:
- A pre-registered meta-analysis (PROSPERO CRD42023402097) was conducted.
- Data from 105 controlled nocebo experiments involving 5017 participants and 391 effect sizes were analyzed.
- Multi-level meta-analysis was used to assess overall effect sizes and identify moderators.
Main Results:
- An overall moderate effect size for nocebo effects was found (g=0.50).
- Symptom expectancy magnitude significantly moderated nocebo effects.
- Technological devices, sham stimulation, and conditioning were associated with large nocebo effects, while verbal suggestion and social observation yielded moderate effects.
Conclusions:
- Nocebo effects are a significant phenomenon influenced by various induction methods.
- Specific methods like technological devices and conditioning are more potent in inducing nocebo effects.
- Enhanced specificity in reporting nocebo induction methods is crucial for understanding their efficacy.
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