ArticleFrontiers in psychiatry2019
Classical Conditioning as a Distinct Mechanism of Placebo Effects.
Article in Frontiers in psychiatry, 2019. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 22 papers, 3 of them syntheses that pooled it.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
22 citing papers in PubMed, 3 syntheses or guidelines pooled it.
- Pooled it
- Placebo effects in low back pain: A systematic review and meta-analysis of the literature.European journal of pain (London, England) · 2021 · on this mapPooled it
- Placebo Analgesia, Nocebo Hyperalgesia, and the Cardiovascular System: A Qualitative Systematic Review.Frontiers in physiology · 2020Pooled it
- Trial
- Roles of administration route, expectation, and belief in placebos in a randomized controlled trial with open-label placebos.Scientific reports · 2025Trial
- Placebo effects in alternative medical treatments for anxiety: false hope or healing potential?CNS spectrums · 2025Trial
- Open-label placebos enhance test performance and reduce anxiety in learner drivers: a randomized controlled trial.Scientific reports · 2024Trial
- μ Opioid Antagonist Naltrexone Partially Abolishes the Antidepressant Placebo Effect and Reduces Orbitofrontal Cortex Encoding of Reinforcement.Biological psychiatry. Cognitive neuroscience and neuroimaging · 2021Trial
- Trial
- Effects of prefrontal transcranial direct current stimulation on open-label placebo responses.Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology · 2026Article
- Commentary: A systematic review of the effectiveness of psychological interventions in organ transplantation.Frontiers in psychology · 2026Article
- The High-Risk Model of Threat Perception Modulates Learning of Placebo and Nocebo Effects and Functional Somatic Disorders.Brain sciences · 2025Review
- The causal role of brain circuits in osteoarthritis pain.Nature reviews. Rheumatology · 2025Review
- Opioidergic activation of the descending pain inhibitory system underlies placebo analgesia.Science advances · 2025Article
- Placebo and nocebo effect in pain.Handbook of clinical neurology · 2025Review
- Placebo hypoalgesia induced by operant conditioning: a comparative study on the effects of verbal, token-based, and social rewards and punishers.Scientific reports · 2023Article
- Article
- Experience with opioids does not modify the brain network involved in expectations of placebo analgesia.The European journal of neuroscience · 2022Article
- The placebo and nocebo effects in functional urology.Nature reviews. Urology · 2022Review
- Operant and classical learning principles underlying mind-body interaction in pain modulation: a pilot fMRI study.Scientific reports · 2021Article
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
1 author.
Funding
No grant is acknowledged in the PubMed record.
Abstract
Classical conditioning was suggested as a mechanism of placebo effects in the 1950s. It was then challenged by response expectancy theory, which proposed that classical conditioning is just one of the means by which expectancies are acquired and changed. According to that account, placebo effects induced by classical conditioning are mediated by expectancies. However, in most of the previous studies, either expectancies were not measured or classical conditioning was combined with verbal suggestions. Thus, on the basis of those studies, it is not possible to conclude whether expectancies are involved in placebo effects induced by pure classical conditioning. Two lines of recent studies have challenged the idea that placebo effects induced by classical conditioning are always mediated by expectancies. First, some recent studies have shown that a hidden conditioning procedure elicits both placebo analgesia and nocebo hyperalgesia, neither of which is predicted by expectancy. Second, there are studies showing that visual cues paired with pain stimuli of high or low intensity induce both placebo analgesia and nocebo hyperalgesia when they are presented subliminally without participants' awareness. The results of both lines of studies suggest that expectancy may not always be involved in placebo effects induced by classical conditioning and that conditioning may be a distinct mechanism of placebo effects. Thus, these results support the idea that placebo effects can be learned by classical conditioning either consciously or unconsciously. However, the existing body of evidence is limited to classically conditioned placebo effects in pain, that is, placebo analgesia and nocebo hyperalgesia.
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Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.