CompletedEarly Phase 1

Direct Comparison of Altered States of Consciousness Induced by LSD and Psilocybin

NCT03604744 · LSD-psilo · University Hospital, Basel, Switzerland

Closed to entry

Status

Not accepting participants

Early Phase 1

Phase

Target enrolment

Study sites

Outside the US

What it is testing

Summary

LSD (lysergic acid diethylamide) and psilocybin (the active substance in "magic mushrooms") are widely used for recreational purposes. Both substances are also increasingly used in psychiatric and psychological research to induce and investigate alterations in waking consciousness and associated brain functions (functional brain imaging, "model psychosis") . However, it has never been studied whether there are differences in the alterations in mind produced by these two substances. Both LSD and psilocybin are thought to induce hallucinations primarily via stimulation of the 5-HT2A receptor. However, there are differences in the receptor activation profiles between the two substances that may also induce different subjective effects. LSD potently stimulates the 5-HT2A receptor but also 5-HT2B/C, 5-HT1 and D1-3 receptors . Psilocin (the active metabolite of the prodrug psilocybin) also stimulates the 5-HT2A receptor but additionally inhibits the 5-HT transporter. In contrast to LSD, psilocybin has no affinity for D2 receptors. Both substances are used in neuroscience as pharmacological tools. However, there are no modern studies comparing these two substances directly within the same clinical study and research subjects and using validated psychometric tools. Therefore, the investigators will compare the acute effects of LSD, psilocybin and placebo.

Summary as written by the trial’s own sponsor and published on ClinicalTrials.gov API v2. It is the sponsor’s description, reproduced unedited, not an assessment by this site.

What counts as success

Primary outcome measures

Altered states of consciousness
Measured over 18 Months

A trial succeeds or fails on its primary outcome, declared in advance. Everything else it reports is secondary by definition.

Who can take part

Eligibility, as published

25 Years to 65 Years

Ages

All

Sex

Accepted

Healthy volunteers

Inclusion Criteria: 1. Age between 25 and 65 years. 2. Understanding of the German language. 3. Understanding the procedures and the risks that are associated with the study. 4. Participants must be willing to adhere to the protocol and sign the consent form. 5. Participants must be willing to refrain from taking illicit psychoactive substances during the study. 6. Participants must be willing to drink only alcohol-free liquids and no coffee, black or green tea, or energy drink after midnight of the evening before the study session, as well as during the study day. 7. Participants must be willing not to drive a traffic vehicle or to operate machines within 48 h after substance administration. 8. Women of childbearing potential must have a negative pregnancy test at the beginning of the study. Pregnancy tests are repeated before each study session. 9. Women of childbearing potential must be willing to use double-barrier birth control 10. Body mass index 18-29 kg/m2. Exclusion Criteria: 1. Chronic or acute medical condition 2. Current or previous major psychiatric disorder 3. Psychotic disorder in first-degree relatives 4. Illicit substance use (with the exception of cannabis) more than 10 times or any time within the previous two months. 5. Pregnant or nursing women. 6. Participation in another clinical trial (currently or within the last 30 days) 7. Use of medications that may interfere with the effects of the study medications (any psychiatric medications) 8. Tobacco smoking (\>10 cigarettes/day) 9. Consumption of alcoholic drinks (\>10/week) 10. Bodyweight \< 50 kg

Where

1 study site

Facility	City	Region	Country
Clinical Pharmacology & Toxicology, University Hospital Basel	Basel	—	Switzerland

On the registry

Contact the trial directly

This site does not enrol anyone and is not involved in this trial. To ask about taking part, use the sponsor’s own contact details on the official registry record, which is also where the most current version of everything above lives.

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NCT03604744 on ClinicalTrials.gov →

Last updated in the registry 2021-04-27. Registry records change; this page reflects the data build of 2026-08-25.

Where this trial sits

Substance

All 48 trials from University Hospital, Basel, Switzerland →