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The psychedelic drug psilocybin (the active ingredient in “magic mushrooms”) may produce lasting, positive changes in personality, new research finds. People who took the drug showed increases in the key personality dimension of openness — being amenable to new ideas, experiences and perspectives — more than a year later.

“It was sort of like an anti-inflammatory for the ego,” says Brian, a 50-year-old scientist, who participated in the research (he declined to reveal his last name). “The swelling went down and I got to see what was underneath.”

Researchers led by Katherine MacLean, a postdoctoral student at Johns Hopkins University, analyzed personality data on 52 participants (average age 46) who had participated in the group’s earlier research on the drug. These volunteers took psilocybin during two to five sessions, at various doses, under highly controlled conditions at the hospital. They were also given personality tests before taking psilocybin, again a couple of months after each drug session, then again about a year later.

The earlier study had found positive psychological changes — documented by both participants and their family members and other associates — in calmness, happiness and kindness. The new research found that the drug takers also saw long-term changes to their underlying personality. “The most surprising thing was that we found a change in personality that is really not expected in healthy adults, not after such a discrete event,” says MacLean.

MORE: ‘Magic Mushrooms’ Can Improve Psychological Health Long Term

While other research has found that some therapies, including intensive meditation, effective treatment with antidepressants or dialectical behavioral therapy to treat borderline personality disorder, can change adult personality, lasting positive change has never been documented as a result of just a few doses of a drug.

The personality changes also ran counter to those expected as people age. Normally, as people grow older, they become increasingly less open to new ideas and new experiences. In contrast, in participants who experienced had what researchers call a “full mystical experience,” the scientists saw a shift toward increased openness, as though the volunteers had become decades younger.

People became more curious and more interested in new ideas and experiences and in trying new things. “It ended up being the best experience of my life,” says 67-year-old retiree Maria Estevez. “It was marvelous, radiant. I felt like I was coming into a magnificent palace, expansive and joyous.”

Those who didn’t have a full mystical experience showed no personality change, however. The researchers defined full mystical experiences as those that engendered the sense that “all is one” and that everything is connected, an experience of having transcended time and space, a sense of sacredness and peace and an inability to describe accurately the experience in words.

Brian’s mushroom trip was exactly that. But it didn’t happen during his first drug session. For his first dose, he had been randomly assigned to get placebo, so he simply sat blindfolded, listening to classical music through headphones in a calm, elegant room attended by a study monitor, whom Brian had met with over the several preceding weeks to prepare for the experiment. “Four hours went by and nothing really happened,” he says.

Meanwhile, Estevez had the opposite initial experience. She was randomized to receive the highest possible dose first, which ended up being the worst experience of her life. “I was slammed, I was inundated, I felt like I was drowning,” she says. “I was knocked around and tumbling beyond all sanity.”

The monitors helped her through it, but she still considered dropping out. She reconsidered after realizing that she might never get another chance to have a better psychedelic experience. Estevez had originally learned about the study in a classified ad, a day after she’d re-read Aldous Huxley’s famous account of his mescaline experience, and wished she could try something similar for her own spiritual exploration.

Indeed, many of the participants in the experiment were self-motivated to enroll, out of curiosity about the effects of magic mushrooms or because they too wanted the opportunity to self-reflect. Many participants already engaged in spiritual activities like meditation, religious services and prayer. That may help explain why they were so sensitive to the effects of the drug, the researchers acknowledged.

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Brian had always been a deeply spiritual man. He had recently been drawn to Eastern religions and the notion that the separation of our selves from the rest of the world was illusory, and said he signed up for the study because he was curious. He jokes that he hadn’t tried psychedelics earlier because “I was actually a victim of my own good judgment in my youth.”

During his experience with a higher dose of psilocybin, he says, “I was just able to drop ego totally and experience the world without all those filters, and experience Brian without all that.”

He describes his experience on the highest possible dose of psilocybin this way:

There was this point where, basically, I forgot about anything Brian-like or who Brian was. I was really in touch with all experience: whatever happened was part of me. I was not observing — I was whatever was happening. The other thing that was so memorable was that everything was so beautiful and it made me cry because the beauty was so exquisite. And then I’d remember how painful and how messy it all was. I was laughing and crying for like three hours straight. I was absolutely that certain that everything was just the same thing, just different flavors and tastes of one underlying reality and being so grateful to be alive and able to experience it.

Brian says that this recognition made him more tolerant and more compassionate. “What was happening to me was real and [yet] the person next to me might not be seeing the same thing. It became absolutely obvious that perspective determines your experience with reality and that maybe being able to take more perspectives than one will give you a more rich and probably more true version of what reality is.”

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In her most positive session, Estevez describes the experience of having a godlike presence with her. “It said to me, ‘Is there anything you want?’ I thought, ‘want?'” says Estevez. “[I knew that] there was this person named Maria in space and time and that she had long lists of things she wanted. That was me. But I just said no. Later, I thought, Wow, if that was case, who was answering?”

Estevez says that she, too, has become more open and empathetic since taking psilocybin. “I am much more forgiving of friends and strangers,” she says. “I’m much more accommodating because I’ve been there, and it really isn’t such a big deal.”

Of course, most drugs that are powerful enough to do good also have the power to do harm, so careful study will be needed to see if long-lasting negative effects also occur.

“We haven’t seen [any evidence of lasting negative effects] in our studies,”says Roland Griffiths, a co-author of the research and professor of behavioral biology at Hopkins. “People can have very negative effects of psilocybin and have anxiety or fearfulness but that’s time-limited, and none of those people report lasting negative effects.”

The researchers are currently seeking participants for a new study on the potentially mood-enhancing effects of psilocybin in current or former cancer patients who are anxious or depressed. (Click here for more info.) The scientists ultimately hope to be able to use psychedelics in treatments for mental illness and to study the nature of consciousness itself.

The new research was published in the Journal of Psychopharmacology.

Updated: The original post did not include the full title of the journal in which the research appeared.

Maia Szalavitz is a health writer for TIME.com. Find her on Twitter at @maiasz. You can also continue the discussion on TIME Healthland‘s Facebook page and on Twitter at @TIMEHealthland.