Acute subjective and behavioral effects of microdoses of LSD in healthy human volunteers
Numerous anecdotal reports suggest that repeated use of very low doses of lysergic acid diethylamide (LSD), known as “microdosing,” improves mood and cognitive function. These effects are consistent both with the known actions of LSD on serotonin receptors, and with limited evidence that higher doses of LSD (100-200 μg) positively bias emotion processing. Yet, the effects of such sub-threshold doses of LSD have not been tested in a controlled laboratory setting. As a first step, we examined the effects of single very low doses of LSD (0 – 26μg) on mood and behavior in healthy volunteers under double-blind conditions.
Healthy young adults (N=20) attended four laboratory sessions during which they received placebo, 6.5μg, 13μg, or 26μg LSD in randomized order at one-week intervals. During expected peak drug effect, they completed mood questionnaires and behavioral tasks assessing emotion processing and cognition. Cardiovascular measures and body temperature were also assessed.
LSD produced dose-related subjective effects across the three doses (6.5μg, 13μg, or 26μg). At the highest dose the drug also increased ratings of “vigor” and slightly decreased positivity ratings of images with positive emotional content. Other mood measures, cognition, and physiological measures were unaffected.
Single “microdoses” of LSD produced orderly dose-related subjective effects in healthy volunteers. These findings indicate that a threshold dose of 13μg of LSD might be used safely in an investigation of repeated administrations. It remains to be determined whether the drug improves mood or cognition in individuals with symptoms of depression.