• Psychedelic Medicine

NEUROSCIENCE | +80 articles

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Psychedelics: How they act on the brain to relieve depression

The Conversation

Up to 30% of people with depression don’t respond to treatment with antidepressants. This may be down to differences in biology between patients and the fact that it often takes a long time to respond to the drugs – with some people giving up after a while. So there is an urgent need to expand the repertoire of drugs available to people with depression.

In recent years, attention has turned to psychedelics such as psilocybin, the active compound in “magic mushrooms”. Despite a number of clinical trials showing that psilocybin can rapidly treat depression, including for cancer-related anxiety and depression, little is known about how psilocybin actually works to relieve depression in the brain.

Now two recent studies, published in The New England Journal of Medicine and Nature Medicine, have shed some light on this mysterious process.

Psilocybin is a hallucinogen that changes the brain’s response to a chemical called serotonin. When broken down by the liver (into “psilocin”), it causes an altered state of consciousness and perception in users.

Previous studies, using functional MRI (fMRI) brain scanning, have shown that psilocybin seems to reduce activity in the medial prefrontal cortex, an area of the brain that helps regulate a number of cognitive functions, including attention, inhibitory control, habits and memory. The compound also decreases connections between this area and the posterior cingulate cortex, an area that may play a role in regulating memory and emotions.

An active connection between these two brain areas is normally a feature of the brain’s “default mode network.” This network is active when we rest and focus internally, perhaps reminiscing about the past, envisioning the future or thinking about ourselves or others.

By reducing the activity of the network, psilocybin may well be removing the constraints of the internal “self” – with users reporting an “opened mind” with increased perception of the world around them.

Interestingly, rumination, a state of being “stuck” in negative thoughts, particularly about oneself, is a hallmark of depression. And we know that patients with higher levels of negative rumination tend to show increased activity of the default mode network compared with other networks at rest – literally becoming less responsive to the world around them.

It remains to be seen, however, if the symptoms of depression cause this altered activity, or if those with a more active default mode network are more prone to depression.

New results

The most compelling evidence of how psilocybin works comes from a double-blind randomised controlled trial (the gold-standard of clinical studies) that compared a group of depressed people taking psilocybin with those taking the existing antidepressant drug escitalopram – something that’s never been done before. The trial was further analysed using fMRI brain scans, and the results were compared with other fMRI findings from another recent clinical trial.

Just one day after the first dose of psilocybin, fMRI measures revealed an overall increase in connectivity between the brain’s various networks, which are typically reduced in those with severe depression. The default mode network was simultaneously reduced, while connectivity between it and other networks was increased – backing up previous, smaller studies.

The dose increased connectivity more in some people than others. But the studies showed that the people who had the biggest boost in connection between networks also had the greatest improvement in their symptoms six months later.

The brains of people taking escitalopram, on the other hand, showed no change in connectivity between the default mode and other brain networks six weeks after treatment started. It is possible that escitalopram may bring about changes at a later time point. But the rapid onset of psilocybin’s antidepressant effect means it may be ideal for people who don’t respond to existing antidepressants.

The study proposes that the observed effect may be due to psilocybin having more concentrated action on receptors in the brain called “serotonergic 5-HT2A receptors” than escitalopram.

These receptors are activated by serotonin and are active throughout network brain areas, including the default mode network. We already know that the level of binding by psilocybin to these receptors leads to psychedelic effects. Exactly how their activation leads to changes in network connectivity is still to be explored though.

The end of traditional antidepressants?

This does raise the question of whether altered activity of the brain’s networks is required for treating depression. Many people taking traditional antidepressants still report an improvement in their symptoms without it. In fact, the study showed that, six weeks after commencing treatment, both groups reported improvement in their symptoms.

According to some depression rating scales, however, psilocybin had the greatest effect on overall mental wellbeing. And a greater proportion of patients treated with psilocybin showed a clinical response compared with those treated with escitalopram (70 percent vs 48 percent). More patients in the psilocybin group were also still in remission at six weeks (57 percent vs 28 percent). The fact that some patients still do not respond to psilocybin, or relapse after treatment, shows just how difficult it can be to treat depression.

What’s more, mental health professionals supported both treatment groups during and after the trial. The success of psilocybin is heavily dependent on the environment in which it is taken. This means it is a bad idea to use it for self-medicating. Also, patients were carefully selected for psilocybin-assisted therapy based on their history to avoid the risk of psychosis and other adverse effects.

Regardless of the caveats, these studies are incredibly promising and move us closer to expanding the available treatment options for patients with depression. What’s more, internalised negative thought processes are not specific to depression. In due course, other disorders, such as addiction or anxiety, may also benefit from psilocybin-assisted therapy.

 
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Clinical Research Unit at The Montreal Neurological Institute

Study maps changes of conscious awareness to neurotransmitter systems*

McGill University | Neuroscience News | 15 Mar 2022

Study reveals how psychedelic drug-induced changes in subjective awareness are rooted in specific neurotransmitter systems.

Psychedelics are now a rapidly growing area of neuroscience and clinical research, one that may produce much-needed new therapies for disorders such as depression and schizophrenia. Yet there is still a lot to know about how these drug agents alter states of consciousness.

In the world’s largest study on psychedelics and the brain, a team of researchers from The Neuro (Montreal Neurological Institute-Hospital) and Department of Biomedical Engineering of McGill University, the Broad Institute at Harvard/MIT, SUNY Downstate Health Sciences University, and Mila—Quebec Artificial Intelligence Institute have shown how drug-induced changes in subjective awareness are anatomically rooted in specific neurotransmitter receptor systems.

The researchers gathered 6,850 testimonials from people who took a range of 27 different psychedelic drugs. In a first-of-its-kind approach, they designed a machine learning strategy to extract commonly used words from the testimonials and link them with the neurotransmitter receptors that likely induced them.

The interdisciplinary team could then associate the subjective experiences with brain regions where the receptor combinations are most commonly found—these turned out to be the lowest and some of the deepest layers of the brain’s information processing layers.

Using thousands of gene transcription probes, the team created a 3D map of the brain receptors and the subjective experiences linked to them, across the whole brain. While psychedelic experience is known to vary widely from person to person, the large testimonial dataset allowed the team to characterize coherent states of conscious experiences with receptors and brain regions across individuals. This supports the theory that new hallucinogenic drug compounds can be designed to reliably create desired mental states.
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Graph showing relation between type of drug, descriptive words and neurotransmitter.

For example, a promising effect of some psychedelics for psychiatric intervention is ego-dissolution—the feeling of being detached with the self. The study found that this feeling was most associated with the receptor serotonin 5-HT2A.

However, other serotonin receptors (5-HT2C, 5-HT1A, 5-HT2B), adrenergic receptors Alpha-2A and Beta-2, as well as the D2 receptor were also linked with the feeling of ego-dissolution. A drug targeting these receptors may be able to reliably create this feeling in patients whom clinicians believe might benefit from it.

“Psychedelic drugs may very well turn out to be the next big thing to improve clinical care of major mental health conditions,” says Professor Danilo Bzdok, the study’s lead author

“Our study provides a first step, a proof of principle that we may be able to build machine learning systems in the future that can accurately predict which neurotransmitter receptor combinations need to be stimulated to induce a specific state of conscious experience in a given person.”

Original Research: Open access.
Trips and neurotransmitters: Discovering principled patterns across 6850 hallucinogenic experiences” by Danilo Bzdok et al. Science Advances

*From the article here :
 
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AI maps psychedelic “trip” experiences to regions of the brain – opening a new route to psychiatric treatments*

Our study shows that it’s possible to map the wildly subjective psychedelic experiences to specific brain regions.

by Sam Friedman and Galen Ballentine | FreeThink | 29 Mar 2022

For the past several decades, psychedelics have been widely stigmatized as dangerous illegal drugs. But a recent surge of academic research into their use to treat psychiatric conditions is spurring a recent shift in public opinion.

Psychedelics are psychotropic drugs: substances that affect your mental state. Other types of psychotropics include antidepressants and anti-anxiety medications. Psychedelics and other types of hallucinogens, however, are unique in their ability to temporarily induce intense hallucinations, emotions and disruptions of self-awareness.

Researchers looking into the therapeutic potential of these effects have found that psychedelics can dramatically reduce symptoms of depression and anxiety, PTSD, substance abuse and other psychiatric conditions. The intense experiences, or “trips,” that psychedelics induce are thought to create a temporary window of cognitive flexibility that allows patients to gain access to elusive parts of their psyches and forge better coping skills and thought patterns.

Precisely how psychedelics create these effects, however, is still unclear. So as researchers in psychiatry and machine learning, we were interested in figuring out how these drugs affect the brain. With artificial intelligence, we were able to map people’s subjective experiences while using psychedelics to specific regions of the brain, down to the molecular level.

Mapping ‘trips’ in the brain

Every psychedelic functions differently in the body, and each of the subjective experiences these drugs create have different therapeutic effects. Mystical type experiences, or feelings of unity and oneness with the world, for example, are associated with decreases in depression and anxiety. Knowing how each psychedelic creates these specific effects in the body can help clinicians optimize their therapeutic use.

To better understand how these subjective effects manifest in the brain, we analyzed over 6,000 written testimonials of hallucinogenic experiences from Erowid Center, an organization that collects and provides information about psychoactive substances. We transformed these testimonials into what’s called a bag-of-words model, which breaks down a given text into individual words and counts how many times each word appears. We then paired the most commonly used words linked to each psychedelic with receptors in the brain that are known to bind to each drug. After using an algorithm to extract the most common subjective experiences associated with these word-receptor pairs, we mapped these experiences onto different brain regions by matching them to the types of receptors present in each area.

Natural language processing, which allows computers to interpret human languages, helped in analyzing subjective psychedelic experiences.
We found both new links and patterns that confirm what’s known in the research literature. For example, changes in sensory perception were associated with a serotonin receptor in the visual cortex of the brain, which binds to a molecule that helps regulate mood and memory. Feelings of transcendence were connected to dopamine and opioid receptors in the salience network, a collection of brain regions involved in managing sensory and emotional input. Auditory hallucinations were linked to a number of receptors spread throughout the auditory cortex.

Our findings also align with the leading hypothesis that psychedelics temporarily reduce top-down executive function, or cognitive processes involved in inhibition, attention and memory, among others, while amplifying brain regions involved in sensory experience.

Why it matters

The U.S. is going through a profound mental health crisis that has been exacerbated by the COVID-19 pandemic. Yet there have been no truly new psychiatric drug treatments since Prozac and other selective serotonin reuptake inhibitors, the most common type of antidepressants, of the 1980s.

Our study shows that it’s possible to map the diverse and wildly subjective psychedelic experiences to specific regions in the brain. These insights may lead to new ways to combine existing or yet to be discovered compounds to produce desired treatment effects for a range of psychiatric conditions.

Pychiatrist Stanislav Grof famously proposed, “Psychedelics, used responsibly and with proper caution, would be for psychiatry what the microscope is to the study of biology and medicine or the telescope for astronomy.” As psychedelics and other hallucinogens become more commonly used clinically and culturally, we believe more research will further illuminate the biological basis of the experiences they invoke and help realize their potential.​

*From the article here :
 
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The Neuroscience of Psychedelic Drugs
Ending Psychedelic Myths, with Professor David Nutt

Technology Networks

Psychedelic drugs have long been exiled to the fringes of medicine, dismissed as recreational drugs with limited therapeutic potential. That all changed with the breakthrough therapy status granted last year to psilocybin, the active compound found in psychedelic mushrooms, for its ability to rapidly reverse treatment-resistant depression. This has led to an explosion of interest in the field, with new institutes opening and new disorders identified as targets for psychedelic therapy. In our latest interview series, we discuss the potential of psychedelics to revolutionize clinical neuroscience with thought leaders in the field.

Professor David Nutt, Edmond J. Safra Professor of Neuropsychopharmacology at Imperial College London, has never been afraid to stick his head above the parapet on the topic of drugs. His repeated calling-out of the failures of contemporary drug policy has seen him butt heads with academics and politicians alike . But there are signs that opinions about the use of drugs in science and society are tilting at last. The opening of Imperial’s Center for Psychedelic Research, where Nutt is Deputy Head, was one clear indication that the wider field is becoming more open to the therapeutic potential of psychedelics. In this interview with Professor Nutt, we discuss pot, policy and the potential of psilocybin.

Ruairi Mackenzie (RM): Two major new centers for psychedelic research, at Imperial and Johns Hopkins, have been established in the last year. How significant are these developments for psychedelic research?

David Nutt (DN):
I think it’s great that there are centers being set up in academic institutions, that’s why we set ours up. The main thing about them is the fact that they’ve been set up in two of the top medical research institutes in the world essentially says that psychedelic research is now accepted as a major branch of medicine, particularly in psychiatry and neuroscience. That’s why they’re so important.

RM: Another recreational drug that has become more widespread in research is cannabis, but the science of cannabis seems less established than the recreational cannabis industry, which has taken off in the US. Do you think the that acceptance of a drug in clinical and recreational use are linked inextricably or are they separate issues?
DN:
Well I think the point to make – I think this is a fundamental point, the most important thing I’m going to tell you – is that our research on the neuroscience of psychedelics was the reason we then moved into the clinic, because our first studies on psilocybin, using FMRI imaging, showed surprising, unexpected brain effects which were predictive, we thought, of it being antidepressant. This antidepressant trial, funded by the MRC, that we conducted was predicated on the neuroscience. It was translational science. The brain changed in the same way as it changes with frequency of depression, so we tried it in depression. It’s forward translational science. That’s completely different from cannabis, where that drug has been widely used therapeutically and eventually the medical profession was dragged screaming and protesting to use it. I believe that our science of psychedelics, particularly psilocybin, has been the driver for us doing it, but it’s also given other people the confidence to move it to the clinic because it is no longer just based on self-report from anecdotes of people using mushrooms in their living room.

RM: The studies involved in using psychedelics are very different from casual use and generally their safety seems to require a controlled environment in which they can be taken therapeutically. Is there a way to make these drugs safe to take outside that environment?

DN:
One of the reasons we were allowed to do the psilocybin depression study was that I persuaded the MHRA that psilocybin was a very safe drug, because we know about a million young people in Britain a year use mushrooms and there’s very little harm.

I have no worries about people using it recreationally, but I do have worries about depressed people using it recreationally because we have found that the effects of psilocybin in depression are usually very difficult, painful and challenging and I would not have been comfortable with people self-medicating in the middle of a mountain in Wales with mushrooms if they go through the kind of trips that our depressed patients went through. If you’re using these for medicine, you need to have appropriate psychotherapy and medical cover. If you’re using them for recreation, well as long as you’re aware of the risks and you’re not suffering from major mental illness, they’re probably relatively safe.

RM: With the treatment of mental health disorders, it seems unlikely we’ll find some kind of cure-all. Which indications are psychedelics most promising for?

DN:
Pretty much all the trials have been done with psilocybin and the areas of clear efficacy are depression – that’s our trial – smoking cessation – that was the Matt Johnson [a Professor at Johns Hopkins] trial and alcoholism, that’s the Michael Bogenschutz [of NYU] trial.

There are also two rather beautiful studies that were blinded studies done in anxiety and depression in people who are facing end of life stress, done by Johns Hopkins and by New York University. Those are the best indications we have at present. There’s also been one rather nice ayahuasca study. Ayahuasca is a preparation of [the psychedelic] DMT. It’s usually used in Latin America, so with ayahuasca, there’s been a Brazilian study showing that Ayahuasca can work in depression.

What links depression, tobacco, smoking and alcoholism, we believed - this is our theory – that in these three indications people’s brain gets locked into a way of thinking from which it is hard to disengage. Smoker’s crave cigarettes; they think about cigarettes enormously when they’re trying to stop, or when they have stopped. Alcoholics crave alcohol; their brain is consumed thinking about alcohol and depressed people’s brains are consumed by depressive ruminations. The common factor in those three disorders is the inability of the brain to disengage from maladaptive brain processes.

What psychedelics do in the actual trip itself is have a powerful disrupting effect on brain circuits which underpin those repetitive processes. It’s that disruption that allows people to escape from disorder. Our belief is that any disorder that is accompanied by what you might called locked-in overthinking, could respond. That could also include other forms of addiction, like heroin addiction. We’re teeing up to do a heroin study soon, but also OCD, where people are over engaged in avoidance and fear of responding, avoiding the fearful consequences.

I do not believe psychedelics will be helpful in disorders such as ADHD or schizophrenia or bipolar disorder, but they will be I think useful with disorders that are internalizing disorders. Disorders where people get locked into an internal mindset from which they can’t escape. We’re also setting up to do a trial in anorexia where people have an excessive preoccupation with body image.

RM: Are there any myths around these drugs that you’d like to disperse?

DN:
Yes! The first is the continual lying about the fact that these are addictive. The United Nations say they’re addictive, the FDA say they’re addictive, the Misuse of Drugs Act says they’re harmful and addictive. These drugs are anti-addictive. They do not cause addiction. One of the reasons they are banned is because people said they were addictive when they’re not; they treat addiction. They don’t cause addiction. The reason they don’t cause addiction is partly because they treat addiction and partly because they produce a very rapid tolerance or desensitization and that occurs so fast that people stop using. There’s a very nice study the US military did, where on the third day the effects wore off. It is one of the reasons they don’t use it in warfare because they realized the Russians could pre-treat their people to develop tolerance for a couple of days. They don’t cause dependence; they don’t cause addiction.

The other myth is they make you crazy. They don’t make you crazy. They might make people who have a propensity to be psychotic more psychotic, but they don’t produce enduring changes in people, negative changes in people’s mental state. If anything they tend to produce enduring positive changes in people. The third myth of course is that they’re very dangerous but as far as I can see there’s almost no deaths from these drugs ever in the history of the world, except from misadventure and of course it is definitely not wise to be taking a psychedelic when you’re sitting on the cliffs in Dover, like a couple of kids did a few years ago at Beachy Head. It’s very silly to go to a place where you are at risk if you’re tripping. In hospital settings, in controlled settings, recreationally these drugs have a low propensity to cause harm.

RM: Psychedelic drugs were very much made out to be dangerous in the 1970s and 1980s, which has hindered research. Is this kind of demonization driven by policy makers or can science play a role now in making sure those same mistakes aren’t repeated?

DN:
The demonization was all political, it all goes back to the Vietnam War, to the fact that young men didn’t want to fight in a war in a place they’d never heard and didn’t want to fight against an enemy they’d never seen for a cause they didn’t understand and they refused to fight. They went to San Francisco, they listened to the Grateful Dead, they took acid and they started the anti-war movement. LSD is the only drug that has ever been banned because it changed the way people voted! In those days, you couldn’t ban a drug just because people were using it, you had to find harm. The hysteria about the harms of psychedelics was all created by the drug enforcement agency and the CIA that justified banning it. Once LSD was banned as is almost always the case, they tried to ban every other drug which might be used instead of it. They banned psilocybin, they banned DMT etc. The banning of these drugs is a political act and it was opposed by many scientists at the time.

RM: Will the establishment of large centers like the ones at Imperial and Hopkins stop scientists being ignored again?

DN:
It’s a great question. I think you need to ask scientists that, they don’t usually tell me the truth. If they like what I do they say it’s great, but if they don’t, they rarely confront me because I’m quite combative! I don’t know what proportion of scientists are on board with [the centers] but a surprising number of very senior people,professors from top institutions around the world have come up to me, by themselves, shaken my hand and said thanks for doing this, we couldn’t do it, but you can, thank you.

There’s a huge stigma against these drugs. Here’s a true story. I wrote a definitive paper on how the regulations, the scheduling of these drugs destroyed research. I wrote in Nature Reviews Neuroscience, about five years ago. The journal contracted it and said the condition was I had to get an American author. I rang up a friend of mine who works in this field in America and I said, great news, we’re going to be contracted to write a Nature Reviews Neuroscience paper on how the drug laws impede research and they said to, “Oh thanks David, but if I put my name to this paper I will never get a grant from the NIH, so I can’t do it. If I do this, they will believe that I’m fighting them, and they won’t fund my research.”

Of course, they’re not funding psychedelic research anyway, but they wouldn’t fund the other research this person was doing. In the end I had to find an American, I found Dave Nichols, even older than me, who was prepared to. He was past getting grants and he was prepared to write it with me. The pressure from NIDA (National Institute on Drug Abuse) and the NIAAA (National Institute on Alcohol Abuse and Alcoholism) and the NIMH (National Institute on Mental Health) on scientists in America to comply with the status quo, which is that these are dangerous illegal drugs, is stopping research.

RM: A final question on another big story – the licensing of esketamine to treat depression – what is your take on these findings?

DN:
It’s very exciting. The thing you need to know about esketamine is it probably works in the same way initially as psilocybin. It disrupts repetitive thinking in depression. It produces similar disorganization of brain connectivity as you get with psilocybin but the esketamine effect doesn’t last very long. It only lasts two or three days. You have to take it twice a week. The [therapeutic] effects of psilocybin, they last for weeks, months or years, not in everyone but in some people. The reason for that is that 5-HT2A receptor which is the target of psilocybin is the receptor which allows you to think differently. esketamine basically causes a disruption of brain functioning, but it doesn’t activate the recovery process whereas psilocybin does.

RM: Do you think the same designation that’s been given to esketamine will be given to psilocybin based on these more enduring results?

DN:
I hope so. There is another fundamental difference. The esketamine is given to people who have not fully responded to an SSRI, but you cannot use psilocybin in those people because SSRIs block the effect of psilocybin. The methodology for the psilocybin trial is that you’ve got to get people off the SSRIs, which is quite difficult sometimes. Esketamine is a sort of top-up, where psilocybin is a different, more powerful medication which you have to have people free of other medication to be able to use it. They will be used in quite different populations, I think.

 
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Psilocybin rewires the brain after depression, study*

by Jason Najum | Microdose | 13 Apr 2022

Published by a team of top researchers at UC San Francisco and Imperial College London — including David Nutt & Robin Carhart-Harris — a new study shows that psilocybin-assisted therapy causes observable changes in brain patterns associated with depression.

Released on Monday in Nature Medicine, the study combines two smaller trials where patients were given psilocybin and traditional SSRIs as placebos, along with psychotherapy talk sessions. The patients also underwent brain scans before and after the sessions.

The scans showed that patients with psilocybin treatment had reduced brain connections in regions associated with depression while increasing connections in other areas of the brain that hadn’t been well-integrated.

Following up on the quantitative analysis were the qualitative results that patients felt a related improvement in their depression symptoms (compared to the SSRI control group), with the effects lasting weeks after treatment.

Psilocybin fosters greater connections between different regions of the brain in depressed people, freeing them up from long-held patterns of rumination and excessive self-focus, according to a new study by scientists at UC San Francisco and Imperial College London.

The discovery points toward a general mechanism through which psychedelics may be acting therapeutically on the brain to alleviate depression and possibly other psychiatric conditions that are marked by fixed patterns of thinking.

Scientists analyzed fMRI brain scans from nearly 60 people who had participated in two psilocybin trials. In the first one, all the participants had treatment-resistant depression and knew they were being given psilocybin. In the second one, the participants were depressed but not as severely, and they were not told whether they had been given psilocybin or a placebo that turned out to be escitalopram, an SSRI antidepressant. In addition to the drugs, all the participants received the same type of psychotherapy.

The scans, which were done before and after treatment, showed the psilocybin treatment reduced connections within brain areas that are tightly connected in depression, including the default mode, salience, and executive networks, and increased connections to other regions of the brain that had not been well integrated.

Participants were also less emotionally avoidant and their cognitive functioning got better. The improvement in their depressive symptoms correlated with changes to their brains, and these changes lasted until the study ended three weeks after the second psilocybin dose. No such changes were seen in the brains of those who received escitalopram, suggesting that psilocybin acts differently on the brain than SSRIs.

Psilocybin and other serotonergic psychedelics like ayahuasca affect 5-HT2A receptors, which are plentiful in brain networks that become overactive in depression. One hypothesis is that the drugs briefly disrupt these connections, giving them a chance to reform in new ways in the ensuing days and weeks.

“In previous studies we had seen a similar effect in the brain when people were scanned whilst on a psychedelic, but here we’re seeing it weeks after treatment for depression, which suggests a carry-over of the acute drug action,” said Robin Carhart-Harris, PhD, who directs the Neuroscape Psychedelics Division at UCSF and is the senior author of the study, which appears April 11, 2022, in Nature Medicine.

“We don’t yet know how long the changes in brain activity seen with psilocybin therapy last, and we need to do more research to understand this,” said Carhart-Harris, who is the Ralph Metzner Distinguished Professor of Neurology, Psychiatry, and Behavioral Sciences and a member of the UCSF Weill Institute for Neurosciences. “We do know that some people relapse, and it may be that after a while their brains revert to the rigid patterns of activity we see in depression.”

The authors caution that while these findings are encouraging, patients with depression should not attempt to self-medicate with psilocybin. The trials took place under controlled, clinical conditions, using a regulated dose formulated in a laboratory, and involved extensive psychological support before, during, and after dosing.

But the study points to a mechanism that, if it holds up, may explain both how psilocybin helps to alleviate depression and potentially other debilitating psychiatric conditions.

“For the first time we find that psilocybin works differently from conventional antidepressants – making the brain more flexible and fluid, and less entrenched in the negative thinking patterns associated with depression,” said David Nutt, DM, head of the Imperial Centre for Psychedelic Research. “This supports our initial predictions and confirms psilocybin could be a real alternative approach to depression treatments.”

*From the article here :
 
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Overall, the results showed psilocybin-induced neural modifications that were fast and enduring.
Single dose of psilocybin found to induce generation of new neural connections*

by Rich Haridy | NEW ATLAS | 5 Jul 2021

An extraordinary new study from a team of scientists at Yale University is reporting the first direct cellular demonstration of a single psilocybin dose inducing neural plasticity in a mammalian brain. The researchers show how the psychedelic prompts rapid growth of neural connections in the frontal cortex of mice and hypothesize this mechanism playing a role in the drug’s antidepressant qualities.

Over the last decade psychedelic science has been accelerating at a rate not seen in half a century. MDMA for PTSD and psilocybin for depression are both in late-stage human trials and on the verge of clinical approval, however, we still know very little about how these psychedelic compounds actually generate their therapeutic effects.

Years of good study into depression have given psychedelic researchers clues to where they should be looking. We know depression is associated with synaptic atrophy in the frontal cortex. We also know rapid-acting anti-depressants can improve mood by reversing these synaptic deficits, essentially increasing the volume of neuronal connections in these key brain regions.

So, do psychedelics promote that same kind of neural plasticity?

This new research, published in the journal Neuron, suggests the answer is yes … at least in mice.

Using chronic two-photon microscopy the researchers imaged the synaptic architecture of the medial frontal cortex in a number of mice. The imaging focused on the number and density of neuronal connections, called dendritic spines. Seven imaging sessions were conducted, beginning before a single dose of psilocybin was administered and stretching up to a month after.

Within 24 hours of that single psychedelic dose the researchers detected increases in dendritic spine size and density. These changes were noted as occurring extremely quickly and also unexpectedly enduring.

One month later a small amount of these new neuronal connections were still present. Alex Kwan, senior author on the study, says it was surprising to see just one dose of psilocybin lead to persistent structural change in the mice brains.

"We not only saw a 10 percent increase in the number of neuronal connections, but also they were on average about 10 percent larger, so the connections were stronger as well," says Kwan. "It was a real surprise to see such enduring changes from just one dose of psilocybin. These new connections may be the structural changes the brain uses to store new experiences."

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Administering psilocybin caused ~10% increases in spine density and spine head width, effects that were observed within 1 day of injection. Some of the newly formed spines persisted 1 month later.

Alongside these structural changes the researchers note functional and behavioral changes were also detected in the animals following the single psilocybin dose. Increased excitatory neurotransmission in the frontal cortex was measured in the mice and stress-related behaviors reduced. This finding suggests these structural brain changes could play a role in some of the therapeutic benefits seen with psychedelics.

Perhaps most interesting is the study’s attempt to disassociate the structural brain changes caused by psilocybin from the drug’s acute psychedelic effects. The researchers used a drug called ketanserin to block 5-HT2 receptors, the pathway by which many believe psychedelic drugs induce their acute “trippy” effects.

Ketanserin effectively stifled head-twitch responses in the animals, which is the primary observational measurement used to track acute psychedelic sensations in mice. But the ketanserin did not block any of the psilocybin-induced brain plasticity changes.

“The possibility to disrupt psilocybin’s acute behavioral effects without abolishing structural plasticity actions has clear implications for treatment in the clinic,” the researchers hypothesize in the study. “However, it is not yet clear if the results will extrapolate to humans.”

Whether the therapeutic actions of psychedelics can be separated from the acute effects is perhaps one of the biggest unanswered questions in psychedelic science. The researchers do note ketanserin is known to only block around 30 percent of 5-HT2 receptors in rodents so it is certainly possible the neural plasticity induced by psilocybin is still mediated through that pathway. A lot more work will be necessary to understand exactly what is going on here, and the jury is certainly still out on whether these psychedelic drugs can generate therapeutic effects without generating an acute psychedelic experience.

The research is the first to directly demonstrate these specific structural neural changes induced by psilocybin in a mammal brain. Another very recent study looking at the effects of a single psilocybin dose in a pig brain saw similar signs of psychedelic-induced neural plasticity. That research saw psilocybin increase levels of a key protein known to enhance neuroplasticity.

The new study was published in the journal Neuron.

Source: Yale University

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