Drug Effects on Mood and Behavior – Expectancy (MESA-X)

This early Phase I, randomised, placebo-controlled trial (n=48) will study the psychological and behavioural effects of a low dose of LSD (13µg) by comparing participants’ experiences when they do or do not know what drug they are receiving.

Conducted by the University of Chicago and supported by the U.S. National Institute on Drug Abuse (NIDA), this trial investigates how expectations (or “expectancy effects”) influence the experience of taking a microdose of LSD. Participants are randomly assigned to one of four groups: (1) told they are receiving LSD and do, (2) told they are receiving LSD but receive placebo, (3) uncertain what they are receiving and are given LSD, or (4) uncertain and receive placebo. The study uses a range of psychological assessments—including visual analogue mood scales, the Drug Effects Questionnaire (DEQ), and the 5D-ASC (a measure of altered states of consciousness)—to evaluate drug effects over a single 4-hour lab session.

By disentangling the pharmacological effects of LSD from the psychological influence of expectation, the researchers aim to clarify how much of the perceived benefit of microdosing is due to the drug itself versus what participants believe they are taking. This has implications for both clinical research and the public discourse surrounding microdosing, especially since much anecdotal support for its benefits may stem from placebo effects. Participants are healthy adults aged 18–40, and the trial is being conducted in Chicago, USA.

Topic Healthy Subjects Microdosing
Compound LSD Placebo
Country United States of America
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Trial Details



Trial Number

Sponsors & Collaborators

University of Chicago
Research with psychedelics is taking place at the Human Behavioral Pharmacology Lab at the University of Chicago.

Data attribution

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