This study with low-dose LSD comprised 2 substudies in different populations of healthy subjects:~Part 1: an open-label dose-escalation study in hallucinogen non-naïve subjects. Part 2: a double blind, placebo controlled, randomised, crossover study in hallucinogen naïve subjects.~Part 1: Open-label, dose escalation study This part was performed in a population of healthy subjects with significant prior experience with hallucinogens. There was a screening period of up to 28 days. Following provision of informed consent and completion of all screening assessments, eligible subjects were assigned to the open-label dose-escalation group.~Following completion of baseline assessments, each subject received a single dose of LSD: 50, 75, or 100 µg. This dose range was selected for assessment based on extensive historical and clinical LSD research. Subjects knew they would receive the experimental drug but were blinded to the dose level received. Subjects were followed up on the day after dosing and at 1 week and 1 month after dosing.~During screening, baseline, treatment, and follow-up, subjects underwent a series of assessments. Included amongst these assessments were cognitive tasks that were administered at baseline before administration of LSD and subsequently during the study. The open-label study subjects also provided samples for PK analysis.~Part 2: Double-blind, placebo controlled, randomised, crossover study This part commenced following evaluation of the results from Part 1. It was performed in a population of healthy subjects with no prior experience with hallucinogens during the last 7 years. There was a screening period of up to 28 days. Following provision of informed consent and completion of all screening assessments, eligible subjects were assigned to 1 of 8 cohorts and then randomly assigned to 1 of 2 treatment groups. Cognitive assessments were administered at baseline before administration of the first dose and subsequently during the study.~Following completion of baseline assessments, subjects entered a 2 week treatment period: the experimental non-crossover group received 2 sequential escalating single doses of LSD administered at levels determined in Part 1 (50 µg followed by 75 µg, or placebo followed by 75 µg), with dosing separated by at least 7 days; the placebo controlled crossover group received placebo followed at least 7 days later by a single dose of 75 µg LSD, as determined in Part 1. Subjects were followed up on the day after each dosing, 1 week after the second dose, and at 1 month after the last dose of study treatment.~During screening, baseline, treatment and follow-up days, subjects underwent a series of assessments.
This study with low-dose LSD comprised 2 substudies in healthy subjects. Subjects who met all inclusion and no exclusion criteria provided written informed consent. Part 1 was an open-label dose-escalation study in hallucinogen non-naïve subjects with significant prior experience with hallucinogens, during which each subject received a single dose of LSD: 50, 75, or 100 µg. Part 2 was a double blind, placebo controlled, randomised, crossover study in hallucinogen naïve subjects with no prior experience with hallucinogens in the last 7 years, during which each subject was assigned to 1 of 8 cohorts and then randomly assigned to receive single doses of LSD 50 µg followed by 75 µg, or placebo followed by 75 µg, with dosing separated by at least 7 days. Subjects were followed up on the day after each dosing, and 1 week and 1 month after the last dose of study treatment. A total of 32 subjects were enrolled.