ArticleScientific reports2023
The difference between 'placebo group' and 'placebo control': a case study in psychedelic microdosing.
Article in Scientific reports, 2023. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 15 papers, 2 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
15 citing papers in PubMed, 2 syntheses or guidelines pooled it.
- Orally derived mesenchymal stem cells in the treatment of vascular diseases: a systematic review and meta-analysis.Scientific reports · 2026Pooled it
- Keeping the promise: a critique of the current state of microdosing research.Frontiers in psychiatry · 2024Pooled it
- Negative affective bias in depression following treatment with psilocybin or escitalopram - a secondary analysis from a randomized trial.Translational psychiatry · 2025Trial
- Subjective and neurocognitive profiling of clinical doses of 3,4-methylenedioxymethamphetamine (MDMA) in healthy volunteers: implications for therapeutic use.Molecular psychiatry · 2026Review
- Measuring and appraising placebo effects in clinical trials: contemporary challenges and approaches in psychiatry.The lancet. Psychiatry · 2026Review
- The science of psychedelic medicine.Nature medicine · 2026Review
- Causal Inference in Studies with Functional Unmasking: Psychedelics and Beyond.medRxiv : the preprint server for health sciences · 2026Article
- Conceptual analysis of mechanisms and methods in psychedelic clinical trial design: a narrative review.Therapeutic advances in psychopharmacology · 2026Review
- On the meaning of "plasticity" in neuroscience and mental health research and its relation to the action of psychedelic therapy.Frontiers in neuroscience · 2026Article
- The Induction of Dissociative States: A Meta-Analysis.Biological psychiatry global open science · 2025Article
- From relaxed beliefs under psychedelics (REBUS) to revised beliefs after psychedelics (REBAS).Scientific reports · 2025Article
- An investigation of acute physiological and psychological moderators of psychedelic-induced personality change among healthy volunteers.Neuroscience applied · 2025Article
- From taboo to treatment: The emergence of psychedelics in the management of pain and opioid use disorder.British journal of clinical pharmacology · 2024Review
- Expectancy Effects Cannot Be Neglected in MDMA-Assisted Therapy Research.ACS chemical neuroscience · 2023Article
- A critical evaluation of QIDS-SR-16 using data from a trial of psilocybin therapy versus escitalopram treatment for depression.Journal of psychopharmacology (Oxford, England) · 2023Article
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
4 authors.
Funding
No grant is acknowledged in the PubMed record.
Abstract
In medical trials, 'blinding' ensures the equal distribution of expectancy effects between treatment arms in theory; however, blinding often fails in practice. We use computational modelling to show how weak blinding, combined with positive treatment expectancy, can lead to an uneven distribution of expectancy effects. We call this 'activated expectancy bias' (AEB) and show that AEB can inflate estimates of treatment effects and create false positive findings. To counteract AEB, we introduce the Correct Guess Rate Curve (CGRC), a statistical tool that can estimate the outcome of a perfectly blinded trial based on data from an imperfectly blinded trial. To demonstrate the impact of AEB and the utility of the CGRC on empirical data, we re-analyzed the 'self-blinding psychedelic microdose trial' dataset. Results suggest that observed placebo-microdose differences are susceptible to AEB and are at risk of being false positive findings, hence, we argue that microdosing can be understood as active placebo. These results highlight the important difference between 'trials with a placebo-control group', i.e., when a placebo control group is formally present, and 'placebo-controlled trials', where patients are genuinely blind. We also present a new blinding integrity assessment tool that is compatible with CGRC and recommend its adoption.
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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.