Take 28 healthy adults, average age 41, who had never taken a psychedelic in their lives. Give each one a 1mg placebo dose, then a month later a 25mg dose of psilocybin. Wire them up for EEG at 1, 2, and 4.5 hours into each session, and scan their brains with MRI before and after both. That’s the design behind Human Brain Changes After First Psilocybin Use, published in Nature Communications by Taylor Lyons of Imperial College London’s Centre for Psychedelic Research and 22 co-authors, and covered Oct 12, 2026 by PsyPost. The finding that should unsettle anyone who assumes a psychedelic experience only “counts” if it leaves a permanent mark: the amount of disorder — entropy, in the technical sense — in a person’s brain activity during the high dose predicted how much lasting insight and well-being they reported a month later. The researchers went looking for a durable structural signature to explain that gain. They mostly didn’t find one. Plotinus never saw an EEG trace. But in the third century CE, he described the identical shape of the thing: a temporary collapse of ordered, step-by-step thought into undifferentiated unity was what produced his most lasting insight — not any permanent alteration to his ordinary reasoning.

The Quick Verdict

Question	What we found
What was studied?	Whether brain entropy during a first psilocybin experience predicts lasting psychological insight and well-being
Who ran it?	Taylor Lyons (Imperial College London Centre for Psychedelic Research) and 22 co-authors, senior author Robin Carhart-Harris
Where and when?	Nature Communications; covered Oct 12, 2026 by PsyPost
Sample	28 psychedelic-naive adults, average age 41, given a 1mg placebo then a 25mg psilocybin dose a month apart
Measurement	EEG at 1, 2, and 4.5 hours post-dose; MRI before and after each session
Core finding	Higher EEG-measured brain entropy during the high dose predicted a ~51-point gain in psychological insight (0–100 scale) and a ~4.7-point gain in well-being (14–70 scale) a month later
Subjective weight	94% rated the high-dose session the most unusual conscious experience of their lives
Structural brain change	Largely absent — lasting changes in brain function a month out were minimal, with only possible, modest white-matter differences
What Plotinus already argued	Henosis, a temporary dissolution of discursive reasoning into unity with the One, produced his most lasting insight — without permanently altering his ordinary rational faculty

The Quick Version

A 2026 Nature Communications study gave 28 psychedelic-naive adults a single dose of psilocybin and found that the more disordered their brain activity got during the trip, the more lasting insight and well-being they reported a month later — even though their brains looked largely unremarkable again by then. Plotinus made the same claim seventeen centuries earlier: his repeated experiences of henosis, a total breakdown of ordered thought into union with the One, were what produced his most durable philosophical and ethical insight. Not a permanent rewiring of his mind. A temporary one, that stuck.

What the Study Actually Found

Most psychedelic research tries to locate the benefit somewhere durable — a new dendritic spine, a rewired default mode network, something you could point to on a scan six months later and say there, that’s the mechanism. Lyons and her Imperial College London colleagues built a study that could actually test whether that’s the right place to look.

Twenty-eight adults, none of whom had ever taken a psychedelic, went through the sequence twice, a month apart: first a 1mg placebo, inactive at that dose, then 25mg of psilocybin. During each session, EEG tracked the electrical complexity of their brain activity at 1, 2, and 4.5 hours in — a measure of “entropy” that, in plain terms, tracks how varied and unpredictable the signal is, as opposed to the repetitive, settled patterns of ordinary waking consciousness. MRI scans before and after each session looked for structural change. And two follow-up questionnaires, one the next day and one a month later, measured psychological insight and overall well-being.

The pattern held across the group: people whose EEG entropy spiked highest during the 25mg session were the same people who reported the largest jump in psychological insight the next day, and that next-day insight was what predicted the well-being gain a month out. Insight scores rose roughly 51 points on a 0-to-100 scale relative to placebo. Well-being rose about 4.7 points on a 14-to-70 scale. Asked months afterward to rate the experience, 94% of participants called the high-dose session the single most unusual state of consciousness they’d ever had.

Here’s the part that cuts against the usual story. When the researchers checked the MRI scans a month later for the kind of lasting structural change that’s supposed to explain psychedelic benefits — new connectivity, altered gray matter, a rewired network — they mostly didn’t find it. Lasting changes in brain function were largely absent. They flagged some possible, modest differences in white matter, but nothing that rose to a clear, durable structural signature. The psychological gains were real and had already held for a month. The brain, by the time anyone went looking for a permanent fingerprint, looked close to how it started.

What Did Plotinus Mean by Henosis?

Henosis (Greek; Plotinus’s Enneads) is the state Plotinus describes as direct union with the One — not a conclusion reached by argument, but a non-discursive experience in which the ordinary distinction between a reasoning self and the object of its thought collapses entirely. Porphyry records that Plotinus called the destination “the flight of the alone to the Alone.”

Plotinus (205–270 CE) spent most of his waking life doing exactly the opposite of what henosis required: teaching in Rome, dictating the dense, step-by-step arguments that became the Enneads, managing the finances and the children of dead friends with what Porphyry’s biography describes as scrupulous, ordinary diligence. He was, by every account, a careful discursive reasoner. That’s exactly what makes his account of henosis worth taking seriously as a parallel rather than a curiosity.

Porphyry, who lived with Plotinus for years, reports that his teacher achieved the “Term” — full union with the One — four separate times during their time together, and that Plotinus himself said he’d experienced it often before Porphyry arrived. Porphyry’s own account of it is strikingly specific: “To this God, I also declare, I, Porphyry, in my sixty-eighth year, was once admitted and entered into Union.” These weren’t vague feelings of oneness. In the Enneads (most explicitly VI.9), Plotinus describes the experience as the total suspension of discursive thought — no subject, no object, no argument, no distance — followed by a return to ordinary reasoning that was unmistakably his, not someone else’s. He didn’t come back from henosis a different thinker. He came back the same careful arguer who had, apparently, touched something his arguments couldn’t reach on their own, and who kept writing treatises about it for the rest of his life.

Why Does Mental Chaos Breed Insight?

1. Ordinary cognition runs on filtering, and filtering is low-entropy. The waking mind mostly suppresses associations it has already decided are irrelevant. That suppression is efficient, but it’s also exactly what keeps most of your thoughts about yourself on the same worn track.
2. Disorder reopens connections the filter had closed. Higher entropy — whether from a psilocybin dose or, in Plotinus’s account, from a sustained practice of philosophical ascent — lets ordinarily unlinked material co-activate, which is what an “insight” actually is: a connection your ordinary filtering wouldn’t have allowed.
3. The benefit lives in the event, not in a stored trace. Since this study found the brain’s functional architecture largely back to baseline a month later, the entropy spike itself — not some lasting rewiring it left behind — looks like the thing doing the work.
4. A temporary collapse of order isn’t the same as damage. Plotinus returned from henosis to write some of the most rigorous metaphysics in the ancient world. The participants in this study returned to ordinary cognition and kept the insight. Disorder, applied briefly, doesn’t have to mean dysfunction.

Why the Study and the Philosophy Rhyme

The claim isn’t “a third-century mystic predicted a 2026 neuroimaging study.” It’s narrower and more interesting than that: Plotinus’s specific position was that the most consequential kind of insight comes from a temporary breakdown of ordered, discursive thought, and that this breakdown doesn’t need to leave a permanent trace on the ordinary reasoning faculty to count as transformative. This study measured the modern, mechanistic version of exactly that claim and found the same shape — entropy during the event, insight the next day, well-being a month later, and a brain that mostly looked like itself again by the time anyone checked.

It connects to the meditation-retreat study covered here before, which found that a week of silent sitting produced neuroplasticity markers resembling a psychedelic state — a slower route to something in the same neighborhood, minus the single dramatic dose. It also sits close to the brain-criticality research on monks practicing Samatha and Vipassana: different meditation styles push the brain toward different positions on the order-versus-disorder spectrum, and which position you’re pushing toward seems to matter for what the practice actually does to you.

It also rhymes with Iris Murdoch’s account of unselfing — her claim that turning attention outward, toward something that isn’t you, is what actually loosens the grip of compulsive self-focused thought. Henosis is unselfing taken to its limit: not attention redirected toward beauty, but the subject-object structure of attention dissolved entirely, if only for a moment. And it belongs next to Plato’s account of eros in the Symposium, the tradition Plotinus inherited and pushed further — desire that reaches past any single object toward something it can never quite hold, which in Plotinus becomes a reaching that can, rarely, briefly, actually arrive.

The Gap Plotinus Didn’t See Coming

Here’s where the comparison gets more interesting than a clean match, and it’s worth sitting with instead of smoothing over.

Plotinus treated henosis as something earned through a long philosophical and ascetic discipline — years of training the soul to turn away from the body and the senses before the One became available even briefly. The entropy spike in this study arrived in under two hours, chemically, in people who had done no such preparation and had no philosophical training at all. Plotinus’s framework has real trouble explaining how a capacity he believed took a lifetime of disciplined ascent to approach showed up, repeatedly, in ordinary office workers and teachers who swallowed a measured dose of mushrooms and sat in a room with an EEG cap on.

That’s not a small gap. It suggests the mechanism Plotinus located in disciplined contemplation isn’t exclusive to it — that something about the human brain can be pushed toward the same kind of radical disorder by a molecule, without the decades of ascetic preparation he assumed were the price of entry. Whether that makes the resulting insight the same thing Plotinus meant by henosis, or something adjacent that merely resembles it, is a question neither the study nor the philosophy settles. Plotinus might say the chemical route gets you to the doorway without doing the work that makes you capable of staying there, or using what’s on the other side of it.

What This Study Doesn’t Show

Be precise about the size of this. The framing invites more confidence than the data earns.

Twenty-Eight People Is Not a Population

This is a small, uncontrolled-for-blinding-failure sample. Participants almost certainly knew which session was the real dose. That’s a real limitation on how confidently these specific numbers generalize.

Correlational Within the Study

The design shows that entropy, next-day insight, and one-month well-being moved together in a consistent pattern. It doesn’t prove entropy caused the insight, rather than some third factor — a person’s general openness to the experience, say — driving both.

”Largely Absent” Isn’t “Zero”

The researchers detected possible, modest white-matter differences a month out. The honest reading is that this study didn’t find the kind of pronounced, lasting structural change you’d expect if structural rewiring were the main story — not that psilocybin provably leaves no trace whatsoever on the brain.

Healthy Volunteers, Not Clinical Patients

Everyone in this sample was screened for psychedelic-naivety and had no diagnosed mental health condition. What entropy-and-insight looks like in someone with depression or PTSD, under clinical supervision, is a related but separate question this study doesn’t answer.

What Actually Follows From This

1. The transformation is in the disorder, not despite it. If you’re inclined to think a powerful experience needs to permanently change your brain architecture to be “real,” this data says otherwise. That upheaval can itself be the mechanism, not just the prelude to one.
2. Insight that doesn’t rewire you can still last. The month-later well-being gains in this study weren’t explained by a structural signature anyone could find. That’s consistent with something closer to Plotinus’s picture: the self that returns from a disordered state can simply choose, and keep choosing, to act on what it saw there.
3. Ask what’s doing the work in your own moments of clarity. Plotinus’s harder question survives the translation into 2026 neuroimaging cleanly: when a flash of insight actually changes how you live, was it because something in you got permanently rewired, or because you got shown something once, clearly enough, that you kept choosing to act like you’d seen it?

Plotinus never ran an EEG and never saw a 0-to-100 insight scale. He had four documented experiences of a thought so total it erased the boundary between himself and what he was thinking about, and a conviction that those experiences, not any lasting change to his ordinary mind, were the real engine of his ethics. Seventeen centuries later, a team at Imperial College London found 28 people whose brains, for a few hours, got measurably more disordered than usual — and who were still, a month on, carrying something that disorder had shown them, in brains that had mostly gone back to looking like everyone else’s.

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This post discusses a 2026 study published in Nature Communications and Plotinus’s Enneads, as recorded by Porphyry in the Life of Plotinus (3rd century CE). The study’s findings are drawn from a sample of 28 psychedelic-naive, healthy adult volunteers and describe correlational patterns between brain entropy, psychological insight, and well-being, not a controlled experiment proving causation or a universal claim about psychedelic use in clinical populations.