Microdose LSD stretched how healthy older adults perceived spans of a few seconds
A controlled trial gave healthy older adults a single microdose of LSD — a barely-perceptible dose — to test whether it changed how they perceived the passage of short spans of time.
Anecdote and older lab work suggest LSD warps the sense of time, but earlier studies were small and poorly controlled. This trial put it to a careful test. Forty-eight healthy adults aged 55 to 75 were split into four groups of 12 and given either a placebo or one of three microdoses of LSD (5, 10, or 20 micrograms). Neither the participants nor the researchers scoring them knew who got real LSD. About three hours later, everyone did a task where they reproduced how long a timed interval lasted. For intervals of roughly two seconds and longer, people on LSD reproduced them as longer than they actually were — a stretching of felt time — strongest at the 10-microgram dose. Notably, this happened without people reporting any obvious change in perception, thinking, or concentration.
In this randomised, double-blind, placebo-controlled between-groups trial, 48 healthy older adults aged 55-75 were randomly assigned to one of four cohorts of 12 — placebo or 5, 10, or 20 μg of LSD — and completed a temporal reproduction task spanning subsecond and suprasecond intervals (800-4000 ms) approximately 3 hours after dosing, with subjective drug effects recorded throughout. LSD conditions were not associated with any robust changes in self-report indices of perception, mentation, or concentration. LSD reliably produced over-reproduction of temporal intervals of 2000 ms and longer, with the effect most pronounced in the 10 μg condition. Hierarchical regression indicated this over-reproduction was independent of marginal differences in self-reported drug effects across conditions. The authors conclude that microdose LSD produces temporal dilation of suprasecond intervals in the absence of subjective alterations of consciousness.
The authors flag several limitations. They describe a small sample size and note the analyses were plausibly underpowered, particularly for dosage effects, with several suggestive convergent effects that might have reached significance in a larger sample. They add that the between-group design (different people in each dose group) provides less internal validity than a within-group design would, so the non-significant dosage effects should be interpreted with caution. They also note the absence of a baseline measurement on the timing task, which would have allowed stronger inferences, and that the sample was comprised entirely of older adults, so the observed changes may not generalize to younger populations. Design-inherent points: this was a single-site trial, and the authors disclosed that five of them were paid consultants of Eleusis Benefit Corporation at the time of the study.
In a randomised, double-blind, placebo-controlled study contrasting placebo with three microdoses of LSD (5, 10, and 20 μg) in older adults, LSD reliably produced over-reproduction of temporal intervals of 2000 ms and longer, most pronounced in the 10 μg dose condition (Yanakieva et al., 2018, Psychopharmacology).
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