Despite strikingly similar psychedelic experiences being reported by people taking synthetic psilocybin and LSD, there are key physiological differences at play.
A recent study, published in the journal Neuropsychopharmacology, found that psilocybin elevated blood pressure more whereas acid had a more significant effect on heart rate.
Researchers at the University Hospital Basel found the main difference between the two substances is LSD kicks in earlier and has a longer duration than psilocybin.
“Both doses of LSD and the high dose of (synthetic) psilocybin produced qualitatively and quantitatively very similar subjective effects, indicating that alterations of mind that are induced by LSD and psilocybin do not differ beyond the effect duration.”
Any differences between acid and synthetic psilocybin are dose-dependent rather than substance-dependent, the researchers explain.
“However, both LSD and psilocybin showed comparable cardio stimulant properties, assessed by the rate-pressure product,” they say. Both LSD and psilocybin significantly increased diastolic and systolic blood pressure, body temperature and pupil size.
According to previous studies, the substances alter consciousness via stimulation of the serotonin 5-hydroxytryptamine-2A (5-HT2A) receptor. But LSD also acts at dopamine D1-3 receptors, whereas psilocin — the active metabolite of psilocybin — inhibits the serotonin transporter.
Photo via ‘Direct comparison of the acute effects of lysergic acid diethylamide and psilocybin in a double-blind placebo-controlled study in healthy subjects’
For the study, 28 participants underwent five 25-hour experimental sessions separated by 10 days, receiving either a placebo, LSD or psilocybin.
Researchers tested two doses for each substance, either 200 micrograms or 100 micrograms of LSD, and 30 milligrams or 15 milligrams of synthetic psilocybin. Participants were randomly given the substances and researchers analyzed the self-reported scales for subjective effects, autonomic effects, adverse effects and various related biomarkers.
At the highest dose of LSD, participants reported higher rates of ego-dissolution, impaired control and cognition, and anxiety than those at a lower dose.
Acid at high doses caused more ineffability — being unable to express words — compared to the higher dose of psilocybin.
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The study mentions how LSD increases blood pressure and body temperature only moderately, while only the high dose of psilocybin causes significantly greater increases in blood pressure and body temperature.
LSD produced a greater increase in heart rate compared to both psilocybin doses. Psilocybin at higher doses, but not the lower dose, caused a moderate increase in heart rate compared to the placebo.
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