Few subjective differences between LSD and psilocybin trips, study finds

A new study published in the journal Neuropsychopharmacology provided the results of one of the first modern clinical investigations of its kind to compare the effects of the psychedelic drugs, lysergic acid diethylamide (LSD) and psilocybin. The researchers recorded few qualitative subjective differences between the two drugs, as the test subjects had difficulty telling them apart.

While LSD is much more potent than psilocybin and other psychedelic compounds at lower doses, comparable joint doses of the two drugs elicited similar effects, as participants found it difficult to separate them. They also weren’t able to easily distinguish medium doses from high doses.

The only thing the participants were good at identifying, in fact, was which sample was the placebo.

The study was conducted by Matthias Liechti from the University of Basel. The researchers observed 28 healthy participants – and about half of the participants had never even taken a psychedelic drug before.

The effects of psilocybin typically last 4-6 hours when taken by mouth, while the effects of LSD extend up to 12 hours or more. Before entering the data, the researchers assumed that the participants would be able to separate the two drug experiences quite easily, as LSD is known to last much longer, but that wasn’t exactly the case.

Study Methods

Each subject performed five different test sessions, with two doses of each drug and a placebo. Subjects received 100 and 200 µg (micrograms) of LSD, or 15 and 30 mg (milligrams) of psilocybin. Similar research has observed the effects using similar doses of LSD. Sessions were double-blind, randomized, and each sample was separated by 10 or more days, presumably to isolate experiments.

A number of physiological and subjective parameters were observed to track the effects of each psychedelic experience. The researchers also monitored blood pressure, heart rate, body temperature, as well as cortisol and oxytocin. Levels of a molecule called brain-derived neurotrophic factor (BDNF) have also been observed, as previous research suggests it may be an effective marker of neurogenesis.

“The subjective effects induced by the two doses of LSD and the 30 mg high dose of psilocybin were broadly comparable, whereas 15 mg of psilocybin exerted significantly weaker effects,” the researchers write in the study. “Evaluations of the 30mg psilocybin high dose nominally fell between the 100 and 200mcg doses of LSD, indicating that 30mg psilocybin corresponds to 150mcg LSD base, a dose that has not been tested here.”

Common doses of psilocybin and LSD seemed to impact blood pressure, heart rate, etc., in relatively similar ways. “By combining elevations in heart rate and blood pressure in the frequency-pressure product, the high dose of psilocybin (30 mg) and the two doses of LSD (100 and 200 µg) exerted an overall similar cardiovascular stimulation, whereas the 15 mg dose of psilocybin exerted weaker effects overall,” the researchers wrote.

The study reported highly effective blinding, meaning that very few subjects correctly chose the drug and dose they were given, except when they were given a placebo.

“In general, the low and high doses were more likely to be confused rather than the high dose being exclusively confused with the low dose,” the researchers said. “Interestingly, this was still the case at the end of the study, despite the clear differences in durations of effect between LSD and psilocybin that may unmask blinding between the substances.”

The researchers found that the altered states caused by 20 mg of psilocybin were comparable to the effects of 100 mcg of LSD. “The 20 mg dose of psilocybin is likely equivalent to the 100 mcg dose of LSD base,” the researchers concluded. “We found no evidence of qualitative differences in altered states of consciousness induced by LSD or psilocybin, except that the duration of action was shorter for psilocybin.”

Early research on LSD and psilocybin

Basel happens to be home to researcher Albert Hofmann’s notorious first intentional trip on LSD. April 19, 1943 is still celebrated to this day as “Bicycle Day” in honor of Hofmann’s bicycle ride on acid – the first time a person intentionally tripped on LSD.

Most people gravitate towards psilocybin because it is perceived to be in a more natural form. But LSD is synthesized from an ergot fungus which is known for its psychedelic and dangerously toxic effects before being processed.

New Atlas reports that pharmacologist Harris Isbell made similar observations of LSD versus psilocybin almost 70 years ago, but his practices were highly unethical. The work was allegedly commissioned by the CIA and involved nonviolent prisoners in jail for narcotics-related offenses.

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