No evidence that LSD microdosing affects recall or the balance between distracter resistance and updating

This randomized double-blind, placebo-controlled preprint study (n=48) compared the effects of three different LSD microdoses (5 μg, 10μg and 20μg) with placebo to determine its effects on modulating working memory recall. Following a delay-match-to-sample task, no evidence was found that LSD microdoses affect memory recall.


“The effect of low doses (<=20 μg) of LSD on working memory, in the absence of altered states of consciousness, remain largely unexplored. Given its possible effects on serotonin 5-HT2A receptors and dopaminergic signalling, it could be hypothesised that LSD microdoses modulate working memory recall. Moreover, in line with computational models, LSD microdoses could exert antagonistic effects on distracter resistance and updating. Here, we tested this hypothesis in a randomised double-blind, placebo-controlled study comparing three different LSD microdoses (5 μg, 10μg and 20μg) with placebo. After capsule administration, participants performed a modified delay-match-to-sample (DMTS) dopamine-sensitive task. The standard DMTS task was modified to include novel items in the delay period between encoding and probe. These novel items either had to be ignored or updated into working memory. There was no evidence that LSD microdoses affected the accuracy or efficiency of working memory recall and there was no evidence for differential effects on ignoring or updating. Due to the small sample of participants, these results are preliminary and larger studies are required to establish whether LSD microdoses affect short-term recall.”

Authors: Sean J. Fallon

Study details

Compounds studied

Topics studied

Study characteristics

48 Humans

Compound Details

The psychedelics given at which dose and how many times

LSD 5 - 20