Decoding the Tripping Brain | The Scientist

© SEAN MCCABE

© SEAN MCCABE


Scientists are beginning to unravel the mechanisms behind the therapeutic effects of psychedelic drugs.


Lying in a room at Imperial College London, surrounded by low lighting and music, Kirk experienced a vivid recollection of visiting his sick mother before she passed away. “I used to go and see my mum in the hospital quite a lot,” recalls Kirk, a middle-aged computer technician who lives in London (he requested we use only his first name). “And a lot of the time she’d be asleep . . . [but] she’d always sense I was there, and after about five minutes she’d wake up, and we’d interact. I kind of went through that again—but it was a kind of letting go.”

Kirk choked up slightly while retelling his experience. “It’s still a little bit emotional,” he says. “The thing I realized [was that] I didn’t want to let go. I wanted to hold on to the grief, because that was the only connection I had with my mum.”

While this may sound like an ordinary therapy session, it was not what you would typically expect. Kirk was experiencing the effects of a 25-mg dose of psilocybin—the active ingredient in psychedelic “magic” mushrooms—which he had ingested as part of a 2015 clinical trial investigating the drug’s therapeutic potential.

After his mother died, Kirk says, he fell into a “deep, dark pit of grief.” Despite antidepressants and regular sessions with a therapist, his condition was not improving. “I was stuck in it for years,” he recalls. So when he heard Imperial College London was recruiting participants for an upcoming trial studying the impact of psilocybin on depression, Kirk decided to sign up.

The study, led by psychologist and neuroscientist Robin Carhart-Harris as part of the Beckley/Imperial Research Program, enrolled 12 patients with varying stages of treatment-resistant depression. Each participant took part in two guided treatment sessions, first with a low dose (10 mg) of psilocybin in pill form, then a high dose (25 mg) one week later. During each psychedelic session, subjects were closely monitored by at least one psychiatrist and an accompanying counselor or psychologist. “The guides [help] provide a safe space for the patient to have their experience,” Carhart-Harris explains.

In addition to the deeply emotional encounter with his deceased mother, Kirk also recalls moments of “absolute joy and pleasure” during his sessions. He remembers having a vision of the Hindu deity Ganesh (the “remover of obstacles”) and feeling an altered sense of self and his surroundings. “Your mind is always chattering and observing things,” Kirk says. “And that was all shut down. For me, there was a feeling of new space.”

Experiences like Kirk’s are common among people who have participated in a psychedelic session (or “trip,” as it was allegedly first called by US Army scientists in the 1950s). Reports consistently include feeling intense emotions, having mystical experiences, and entering a dreamlike state. Many also articulate a dissolving sense of a bounded self, coupled with a feeling of increased connectedness with others and the rest of the world.

When Carhart-Harris and his team assessed their study’s participants three months after treatment, they found that most of the participants showed reduced depressive symptoms, with 5 of the 12 in complete remission1—including Kirk. It’s now been two years since he received psilocybin therapy, and he says that he has not needed antidepressants or therapy since. “I got a new positivity that I didn’t have for some time,” he says.

These results are preliminary—the study tested a small sample size with no control group. But other recent trials, including some that were larger and included controls, have revealed additional therapeutic benefits. Last December, for example, two randomized placebo-controlled clinical trials of psilocybin in terminal cancer patients (51 and 29 patients, respectively) found that giving participants psilocybin in guided sessions could substantially decrease depression and anxiety—an improvement that persisted for at least six months after treatment. 2,3 In smaller pilot studies, psilocybin has also shown success in treating addiction. In two small trials, one involving smokers4 and the other alcoholics,5 most participants remained abstinent for months after treatment with the psychedelic.

A number of early studies have also reported evidence that other psychedelics, primarily lysergic acid diethylamide (LSD), have similar effects. Roland Griffiths, a psychiatry professor at Johns Hopkins University, describes the effects of psychedelics as a sort of “reverse PTSD” (posttraumatic stress disorder). With PTSD, there is “some discrete, traumatic event that produces some alteration in neurology and perception that produces [psychological] dysregulation going forward,” he says. In a similar but opposite way, treatment with hallucinogenic substances is a “discrete event that occurs to which people attribute positive changes that endure into the future.” While scientists are only beginning to understand the mechanisms behind these effects, what they’ve found so far already tells quite a compelling story.

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Diana KwonComment