In the ’60s, leaders of the US psychedelic movement were a little nuts. Some 60 years later, though, a new psychedelic movement — particularly the academic and medical spheres — has traded in mandala beads and tie-dye for clinical trials and peer review (at least during business hours). But the ideas about psychedelic consciousness are as exciting, incisive, and intriguing as ever — and behind many of the major theories driving the field forward, you’ll find Robin Carhart-Harris.

Carhart-Harris is a professor of neurology at the University of California San Francisco (UCSF). As a graduate student studying psychoanalysis at Brunel University, he was gripped by the idea that there exists a hidden oasis of the mind — the unconscious. But it seemed deeper than the tools of psychoanalysis could reach. Free association, hypnosis, and dreams were anything but conclusive. “I thought if the unconscious is real, could drugs reveal it?” he recalls.

In 2008, after receiving a PhD in psychopharmacology from the University of Bristol, Carhart-Harris joined Imperial College London and ensconced himself in academic research on psychedelic drugs. There, he published one of the UK’s first papers on psilocybin and eventually founded the Centre for Psychedelic Research in 2019, the world’s first major academic research center focused on psychedelics.

In 2014, he published the “entropic brain” hypothesis, identifying neural entropy — more complex brain activity, roughly — as a key feature of the tripping brain. Along with neuroscientist Karl Friston, he subsequently refined that into the REBUS model, or RElaxed Beliefs Under pSychedelics (even the acronym is a little trippy), which remains among the most influential explanations of what psychedelics do to the mind.

It sees perception, cognition, and emotions as ordinarily constrained by the brain’s beliefs about the world. Like water held inside a jar, those beliefs give shape to our experiences. REBUS suggests that psychedelics relax those beliefs, making that jar’s boundary more porous. Sensory data from outside those beliefs is let in, while the character of experience can also “break out” of its usual forms.

REBUS began to paint a picture of why psychedelics seem to have such therapeutic success in breaking free of pathological habits (together with therapy that helps form healthier ones). Then, in 2023, Carhart-Harris published another paper on the idea of canalization, drawing on REBUS to formalize what amounts to a general theory of mental disorders.

In 1890, the American psychologist William James described consciousness as a flowing river. Canalization extends that idea — rivers carve their river beds over time, entrenching themselves deeper into the landscape. The mind works similarly, carving mental and behavioral patterns into itself. The deeper they get, the more “stuck” in them the mind becomes. Psychopathologies can be understood as harmful patterns — like self-criticism, anxiety, or depression — that are dug so deep, we can’t get out of them. But psychedelics, by dialing up the brain’s plasticity, can temporarily fill in the riverbeds, making it easier to shift toward different behaviors.

In addition to exploring how psychedelics work, Carhart-Harris has published widely on whether they work as therapies. That includes studying the joint approach of psychedelics and therapy, comparing psilocybin to antidepressant medication, and seeing whether a single dose of psilocybin can benefit those with treatment-resistant episodes of major depression. In each case, the results continue to support a clear — if cautious — optimism.

Despite the promising results, Carhart-Harris is particularly attuned to something that the psychedelic pioneers of the ’60s were not: a clear account of the risks. His public messaging is careful not to overstep what the research can support, and the website for his lab at UCSF has an entire video series dedicated to best practices for harm reduction.

Everything the researchers of the past few decades have learned about psychedelics has come in spite of their continued classification as illegal Schedule I substances. If psychedelics are indeed telescopes for the mind (as the psychiatrist Stanislav Grof put it), the zoom has been held back to zero. But we’re now on the verge of expected Food and Drug Administration approval of both MDMA and psilocybin, which could further invigorate an already-exciting area of research.

At 43 years old and at the helm of his newly minted lab at UCSF — a poetic return to the site of America’s last major psychedelic scene — Carhart-Harris is just getting started on his trip.