Clinical trials have shown LSD (Lysergic acid diethylamide)—the most common hallucinogen—to be a promising treatment for mental health disorders. But previous studies involved a single dose of LSD rather than a range of dosing options. Furthermore, there was no recent data available on the acute effects of different well-defined psychoactive doses of LSD in humans.
A group of researchers from the University of Basel’s Department of Biomedicine in Switzerland, set out to better understand the acute subjective and autonomic effects of LSD across a range of relevant doses. Identifying the optimal dose can help researchers select the right dose for future trials in patients with anxiety and depression, the researchers said.
The study involved six sessions under double-blind conditions, meaning that neither the patient nor the doctor administering the medication knew which dose the patient received. Participants included eight men and eight women. Medications and dosages tested included a placebo, one of four different doses of LSD (25 micrograms, 50mcg, 100mcg, 200mcg), and a high dose of LSD (200mcg) combined with Ketensin (ketanserin), an antihypertensive drug that blocks the effects of LSD. Doses were administered at least 10 days apart.
Researchers found that all four doses of LSD increased “oceanic boundlessness” and “visionary re-structurization.” The 25mcg dose was the only one that was not associated with “ego dissolution,” also known as ego death, or the complete loss of subjective self-identity.
A “ceiling effect” was identified with the 100mcg dose with no significant differences seen in positive subjective effects between the 100mcg and 200mcg doses. However, the 200mcg dose induced significant anxiety in subjects. But when Ketensin was combined with the same dose of LSD, the antihypertensive markedly reduced the psychedelic effects to a level comparable to the 25mcg dose of LSD.
Researchers also noted only moderate elevations of arterial blood pressure and rate in participants who received dosages of LSD.
The study, titled “Acute dose-dependent effects of lysergic acid diethylamide in a double-blind placebo-controlled study in healthy subjects,” is published in the journal Neuropsychopharmacology.
