Why Is Salvia Such a Uniquely Terrifying Drug?

Bad trips are a looming possibility when consuming any hallucinogenic drug, but one seems to evoke terror more predictably than the rest: salvia.

A uniquely potent and psychedelic plant, salvia is no LSD. Indeed, the trip it elicits is so intense and dizzying that it was deemed an "atypical psychedelic"—one even the most experienced trippers may struggle to enjoy—at this past weekend's eighth annual Horizons psychedelics conference. At the appropriately mystical Judson Memorial Church in downtown Manhattan, a couple hundred students, dreadlocked trippers, and middle-aged advocate types received an earful on how—and why—salvia makes you trip harder, and weirder, than pretty much anything else.

By exciting the brain's serotonin receptors and other neurological pathways, panelists told an audience nodding in fervent agreement, psychedelic drugs create a feeling of inner peace and acceptance that can help mitigate conditions like addiction to opioids, cancer-related anxiety, and PTSD. Words like "openness to new experience," ego death," "spirituality," and "connectivity" bounced off the calm blue walls, stained-glass windows, and Romanesque columns and arches.

But of all the psychedelics discussed, salvia—technically Salvia divinorum—was deemed special in terms of both the kinds of hallucinations experienced and the mechanism by which the drug affects the brain.

In fact, salvia offers a singular trip, with "nothing else remotely like it," according to Dr. Peter H. Addy, a research associate at Yale who has studied the substance for five years.

"The main effect is tactile hallucinations," he said. The feeling is kind of like a bug crawling on your skin. Salvia also "leads to a kind of synesthesia [the crossing of senses so that stimulation of one provides a sensation in another] I've never seen before in the literature," he continued.

While visual-auditory synesthesia is often reported with LSD use (users claim the ability to "see" music, for instance), salvia causes visual and tactile synesthesia, meaning "you see things and feel them in your body," as Dr. Addy put it. A subject in one of his studies told the researcher he "could see everything going on in the room, but he could see it through his skin, not through his eyes."

Part of what sets salvia apart is its peculiar chemistry. While salvinorin A—the psychotropic molecule in Salvia divinorum—binds only to the dopamine-reducing kappa-opioid receptor, most psychedelics increase serotonin by binding to the serotonin 5-HT2A receptor, among others.

"These [drugs] are operating on completely different pathways," Dr. Addy explained to his flock.

Though salvia is a k-opioid receptor agonist (meaning it activates the receptor, rather than blocking it like antagonists), it does not share similarities with opioids like morphine or heroin. "Morphine is the typical mu-opioid agonist," Dr. Addy said, increasing dopamine—a big player in the brain's reward system—and leading to "analgesic effects, euphoria, compulsive use, and addiction." A k-opioid agonist like salvia, on other hand, reduces dopamine levels "in the same brain circuit."

"If morphine causes euphoria," Dr. Addy said, "a kappa agonist causes dysphoria."

Still, this dire state is "not quite uncontrollable sadness and weeping and gnashing of teeth," but "more of a disassociation of the warmth and familiarity with your body and human connections," he explained.

Contributing to salvia's novelty status, Dr. Addy later told me, is that it is a drug "very few people would consider to be fun in any way."

The most potent naturally occurring psychedelic (many popular drugs like LSD are synthetic), salvia is so intense that "everything's fine and then two seconds later, everything is chaotic and different and I don't even have feet anymore," he joked at one point to the crowd. "In short, salvia is unique and mysterious, and it has a lot of potential to tell us about ourselves and our bodies."

In the course of his studies, Dr. Addy traveled with Xka Pastora, a nonprofit group documenting traditional uses of salvia, to the Sierra Mazateca mountains in southern Mexico. There, the Mazatec people have a long history of using salvia "as a powerful medicine" in religious ceremonies, and their ritualistic focus on the drug provides a glimpse into how the its effects might be channeled toward therapeutic purposes. While the historical use of many naturally occurring and synthetic psychedelics is well-documented, "There is a whole lot that we don't know about the traditional use of salvia," especially in the pre-colonial era of Mexico, Dr. Addy said.

On his trip to the Sierra Mazateca mountains, Dr. Addy gained some insight into the Mazatecs' relationship with the stuff. For starters, they believe that salvia is an embodiment of the Virgin Mary, and that ingesting it may allow one to speak with her, St. Peter (the gate-keeper to Heaven), and even Jesus Christ himself.

"Xka pastora [salvia's traditional name] roughly translates to 'leaves of the shepherdess,' though sheep and shepherdess are not native to Mexico," Dr. Addy said. "Locals also call it hierba de Maria, the herb of Mary," but this provides little insight into the religious use of salvia before the Spanish conquest of the 1500s brought Catholicism to the region.

"Other than the Virgin Mary," he said, "we don't know what to call it."

What Dr. Addy does know is that the Mazatec people take the process of ingesting salvia very seriously. Following strict preparation guidelines, the ritualistic consumption of salvia requires "near or total darkness" to protect the plant—whose energy is believed to be "timid like a deer"—from bright lights that might frighten her away.

Participants gather around an altar (often dedicated to the Virgin Mary) and chew on the raw, blessed leaves, or else drink them as a watery liquid before joining in ritualistic singing and chanting, a trip that lasts about three hours.

One thing we can learn from the Mazatecs is that smoking salvia is not the ideal ingestion method. While the Mazatec rituals last hours, smoking salvia produces intense effects for no longer than about 20 minutes.

The natural habitat of salvia is disputed, but "what we do know is that in pretty much every area growing salvia, it was put there on purpose by humans," according to Dr. Addy. "It's a cultigen," meaning that it rarely seeds.

But despite humans' desire to cultivate salvia, Dr. Addy made no bones about the drug's fear-inducing qualities. One audience member asked about a Center for Cognitive Liberty and Ethics study that emphasized its "terrifying" effects, while another made a cheeky inquiry about the doctor's encounters with the "utter conviction that what you just did has started a chain of events that will imminently lead to the apocalypse" among salvia users.

The profound, disorienting effects of salvia create an experience that few people have sought out, despite its continued existence as a federally legal psychedelic. "It's not a party drug," nor is it popular, Dr. Addy said. As a result, from a policy perspective, "It's just kind of stayed under the radar."

While some states ban sale of the substance to minors and more than 15 ban its sale flat-out, the drug is still sold in head shops and gas stations around the country.

So has Dr. Addy experimented with the drug he is professionally dedicated to exploring? A woman in his audience with short, graying hair stood up and asked that very question.

"I neither agree nor disagree with those sorts of statements," he replied, to much applause. "That's the thing about academia. If I say that I took the drugs, then I can't do any real research because I'm 'biased.' If I say I have not taken drugs, I can't be believed because I don't know what anyone's talking about."

Follow Kristen Gwynne on Twitter.