“Repeated Low Doses of LSD in Healthy Adults: A Placebo-Controlled, Dose-Response Study”, 2022-02-01 (; backlinks; similar):
The resurgence of interest in using psychedelic drugs, including lysergic acid diethylamide (LSD), in psychiatry has drawn attention to the medically unsupervised practice of ‘microdosing’. Thousands of users claim that very low doses of LSD, taken at 3–4-day intervals, improve mood and cognitive function., However, few controlled studies have described the effects of the drug when taken in this way.
Here, in a double-blind controlled study, we studied the effects of 4 repeated doses of LSD tartrate (13 or 26 μg) or placebo, administered to healthy adults at 3–4 day intervals, on mood, cognitive performance and responses to emotional tasks. Participants were randomly assigned to one of 3 drug conditions: placebo (n = 18), 13 μg LSD (n = 19), or 26 μg LSD (n = 19). They attended 4 5-hour drug-administration sessions separated by 3–4 days, followed by a drug-free follow-up session 3–4 days after the last session.
[Measures: Depression, Anxiety and Stress Scale / Positive and Negative Affect Scale / Addiction Research Center Inventory, Drug Effects Questionnaire, Profile of Mood States (POMS); heart rate / blood pressure; Digital Symbol Substitution Test (DSST) / n-back; Cyberball Emotional Images Task / Emotional Faces Task; 5D-ASC]
LSD (26 μg) produced modest subjective effects including increased ratings of ‘feeling a drug effect’ and both stimulant-like and LSD-like effects, but the drug did not improve mood or affect performance on psychomotor or most emotional tasks. No residual effects were detected on mood or task performance on the drug-free follow-up session.
We conclude that within the context of a controlled setting and a limited number of administrations, repeated low doses of LSD are safe, but produce negligible changes in mood or cognition in healthy volunteers.
[Keywords: behavior, cognition, LSD microdosing, mood, psychopharmacology]
…3.7.3 Cognitive performance: The LSD (13 or 26 μg) groups did not differ from placebo on the n-back or DSST tasks on session 5 (Figure 9). Interestingly, when subjects were asked to rate (on a 7-point scale) how well they thought they performed on the task, subjects in the high-microdose LSD group self-reported performing statistically-significantly above average relative to other participants (one-way ANOVA: drug, F2,49 = 3.86, p = 0.028, 26 μg vs. placebo, p < 0.050) and statistically-significantly better compared with the first time they completed the task (one-way ANOVA: drug, F2,49 = 4.77, p = 0.013, 26 μg vs. placebo, p < 0.050).
…Discussion: During the 4 drug administration sessions, LSD (26 μg) produced modest, dose-related increases in stimulant-like (ARCI A and POMS Vigor) and LSD-like effects (ARCI) and ratings of ‘feeling a drug effect’ during the sessions. These effects appeared to be stronger on the earlier sessions. The drug had no effect on most cognitive or emotional tasks or on cardiovascular measures, except for a small decrease in false alarm rates for recognizing fearful emotions, a decrease in feelings of rejection on the social rejection task and a non-statistically-significant trend for improved performance on the DSST. Most subjects did not correctly identify the drug as a hallucinogen/psychedelic at either dose. There were no lasting effects of the drug on mood or cognitive or emotional performance on the follow-up session…We note that self-reported anxiety and depression ratings, as measured by the DASS, declined substantially from the initial screening to the first study session and then to the follow-up up session, regardless of what drug the participants received.