The journal published a new study NeuropsychopharmacologyThese results were based on one of the most modern clinical investigations to date. It compared the effects of two psychedelic drugs: lysergic acid derthylamide, (LSD), and psilocybin. The researchers found few differences in the subjective quality of both drugs as subjects struggled to distinguish them.

LSD can be more powerful than psilocybin or other psychedelic substances at lower doses. However, participants experienced similar effects with comparable doses. Participants had difficulty distinguishing the drugs from each other. They were also unable to distinguish between higher and lower doses.

Participants were unable to identify which placebo sample they had.

The study was led by the University of Basel’s Matthias Liechti. Researchers observed 28 healthy participants—and about half of the participants had never even taken a psychedelic drug before.

Psilocybin effects last for 4-6 hours if taken orally. LSD effects can last up to 12 hours. Before going into the data, researchers assumed that participants would be able to separate the two drug experiences fairly easily, as LSD is known to last much longer, but that wasn’t exactly the case.

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Five different testing sessions were conducted on each subject. Each session included two doses (micrograms) of LSD and one placebo. Subjects were given 100 and 200 µg (micrograms) of LSD, or 15 and 30 mg (milligrams) of psilocybin. Similar studies have shown similar effects with LSD. The sessions were double-blinded, randomized, and each sample was separated by 10 days or more—presumably to isolate the experiences.

The effects of each psychedelic event were tracked by examining a number of subjective and physiological parameters. The effects of each psychedelic experience were also tracked by researchers who monitored body temperature and blood pressure. As past research has suggested, BDNF could also be an indicator of neurogenesis.

“Subjective effects that were induced by both doses of LSD and the high 30 mg dose of psilocybin were largely comparable, whereas 15 mg psilocybin exerted clearly weaker effects,” the researchers write in the study. “Ratings of the high 30 mg psilocybin dose were nominally between the 100 and 200 µg doses of LSD, indicating that 30 mg psilocybin corresponds to 150 µg LSD base, a dose that was not tested herein.”

LSD and psilocybin both had similar impacts on blood pressure, heart beat, and other parameters. “When combining elevations of heart rate and blood pressure into the rate-pressure product, the high dose of psilocybin (30 mg) and both doses of LSD (100 and 200 µg) exerted overall similar cardiovascular stimulation, whereas the 15 mg dose of psilocybin exerted overall weaker effects,” the researchers wrote.

The study reported very effective blinding—meaning that very few subjects correctly picked which drug and dose they had been administered, apart from when they were given a placebo.

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

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

LSD Early Research and Psilocybin Research

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 bike ride on acid—the first time any person intentionally tripped on LSD.

People gravitate to psilocybin as it’s more natural. LSD is created from ergot, which is a fungus known for its dangerously poisonous and psychedelic effects.

New Atlas reports that pharmacologist Harris Isbell conducted similar observations of LSD versus psilocybin nearly 70 years ago—but his practices were highly unethical. This work was allegedly done at the request by the CIA and involved nonviolent inmates who had been convicted of narcotic offenses.