Marijuana and toxicology in ancient Greece and Rome

The words toxic and intoxicated were derived from the Greek word toxon, which refers to a bow and arrow that featured arrowheads dipped in poison. The poison was sufficient in most cases to kill a soldier on the battlefield, even if the arrow missed a vital organ. An infected wound by itself could be lethal. Only 45 percent of people given medical treatments survived severe infections brought on by wounds or surgical procedures like amputations. It was a time when the average lifespan was 26 years. Just four-percent of the population made it past age fifty. A thorough knowledge and ability to identify medicines and poisons was critical to survival.

Hippocrates, Galen, Celsus, and other medical practitioners were skilled enough to know that a substance that could kill a person could also treat them for pain or cure an illness. It was just a matter of dosage and balancing different medical objectives. Examples included opium and hemlock. Hemlock, the poison used in 399 BCE by anti-intellectuals to execute the anti-authoritarian philosopher Socrates, the alleged corruptor of little Greek children’s respect for authority, fell into this category. Hemlock’s active neurotoxin, coniine, is a sedative and anti-spasmodic. It can also treat arthritis and joint pain. However, its effective dose is so close to its lethal dose that it isn’t practical for medical use.

Absent from the pharmacopeia of dangerously toxic substances was cannabis. Dipping an arrowhead into hash oil didn’t do anything in terms of harming the enemy. Hashish didn’t kill anyone who consumed it, including Socrates or the physicians Galen or Hippocrates. It’s even possible it could benefit a wounded recipient. Modern research indicates THC and CBD possess anti-microbial activities that can affect bacterial membranes and interfere with virulent infections. Lacking any harmful side effects, the early Greeks and Romans never considered hashish or marijuana to be a toxin or toxic, something that interferes with the reproduction of human cells.

Marijuana’s nontoxicity challenges the belief that the herb fits the category defined as intoxicating in the same sense as alcohol, opioids, or Cupid’s arrow. Religious groups such as Islam, Christianity, Buddhism, Mormonism, Christian Science, and the Baháʼí Faith base their rejections of cannabis on presumptions that it intoxicates. If cannabis fails in the literal sense of the word to be lethal in large enough dosages, then how does it intoxicate?

Users know marijuana’s effects are different from anything else listed in Schedule I or Schedule III of the Controlled Substances Act (CSA). It clearly deserves its own unique classification, as well as unique subcategories for its useful components. The CSA itself could use a complete makeover. Its five categories are too few to cover the full spectrum of different drug effects it encompasses. Potentially fatal chemical compounds end up being misclassified together along with non-toxic substances.

The confusion comes as no surprise. The CSA was signed into law on October 27, 1970, by President Richard M. Nixon, making it the fruit of a poisonous tree that resulted in a new type of drug war and added to the systemic social inequalities among different races and cultures.

Other substances miscataloged in Schedule I due to politics or hysteria include psychedelics like psilocybin, MDMA, ibogaine, DMT, mescaline, and LSD. These compounds are often rejected because they are seen as challenging the boundaries of mind-body duality. Certain religious groups still maintain that matter possesses two distinct forms, living and non-living, and that the distinction is absolute. In theology it’s called vitalism. Vitalism asserts that an inert or non-living substance cannot affect the mind, the soul, or the élan vital without an intermediary spiritual force being present. The spiritual force is always presumed to be satanic. Thus, these substances are still viewed by some as demonic, as poisonous to the soul.

The vitalist theological controversy was resolved in 1828 when a talented and famous young German chemist named Dr. Friedrich Wöhler discovered how to make urea, the organic chemical found in urine, a “living chemical,” using only non-living chemicals. His discovery meant living and non-living chemicals were essentially the same thing, that both are chemicals. Wöhler is considered to be the father of organic or carbon-based chemistry. Vitalism has since been discarded as a pseudoscience.

If anything can be said to be toxic, it’s the drug war. Since 1970, the drug war’s failure to stem addictions and drug-related accidents has resulted in estimates of 1.1 million deaths from overdoses. Drug cartels and drug enforcement activities have added to the mortality. In fifty years, the U.S. has spent at least $1 trillion dollars on enforcement, much of it related to incarceration costs. The global cocaine supply has since increased by 400-percent. Marijuana is well on its way to becoming a staple commodity in free countries throughout the world. The intoxicating lure of drug enforcement funding still attracts thousands of grifters addicted to the drug war in ways that seek to capitalize on it or weaponize it in some political or tribal fashion. In terms of actual toxicity, America’s drug war needs to be put on the CSA’s Schedule I because it fits the three primary Schedule I criteria: It possesses a greater potential for abuse than drugs, it has no accepted medical use, and it is unsafe.

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13 Responses to Marijuana and toxicology in ancient Greece and Rome

  1. Speaking of Socrates, I wonder if you have seen the video “Socrates versus Freedom” by Filthy Heretic?

    • Servetus says:

      I checked out the Filthy Heretic and Socrates versus Freedom. He’s good at heresy and he covers more material than I do. I didn’t find too much related to drugs beyond the psychedelic graphics. I did find some people on the web who had invented a cocktail called the Filthy Heretic…take two parts vodka, one part tart cherry juice, one part simple syrup, one part fresh lemon juice, one-half part chambord. Shake with ice and pour into a martini glass.

  2. Servetus says:

    Researchers are investigating psychedelics and sex. Participation in future research is provided through an updated survey available to anyone interested in joining.

    31-Mar-2025 — A team of researchers has just published the first paper of its kind reporting on the impact of psychedelics on sexuality and intimacy. The paper, published Friday (March 28) in the Journal of Sex Research, found that psychedelic experiences enhanced participants’ perceptions of their relationship quality, attraction to their current partner, and sexual activities.

    “People in clinical trials and people going on psychedelic retreats in other countries have talked about a broad range of positive effects, including greater self-insight and feeling more connected to other people. Could there be benefits for intimate relationships in the long-term?” says Daniel Kruger, PhD, research associate professor in the University at Buffalo School of Public Health and Health Professions and first author on the paper. […]

    Researchers sent a survey to nearly 600 individuals who have used psychedelics, querying them on how their use of psychedelics affected various aspects of their sexuality, gender identity, and romantic relationships. The most common psychedelics that participants reported using were psilocybin mushrooms, LSD, ecstasy or molly, and ketamine.

    The results found that 70% of participants reported perceived impacts of psychedelic experiences on their sexuality and/or sexual experiences, with 65% mentioning short-term effects and nearly 53% reporting long-term effects. […]

    As this was the first study of its kind, it was meant to be broad and exploratory, according to Kruger, who plans to conduct further research to better understand what’s happening. They have launched an updated version of the survey, which can be taken anonymously by adults who have used psychedelics.

    AAAS Public Science News Release: Psychedelics and sex: New research explores perceived impacts on sexuality and intimacy

    The Journal of Sex Research: Perceived Impact of Psychedelics on Sexual, Gender, and Intimate Relationship Dynamics: A Mixed-Methods Investigation”

    Authors: Daniel J. Kruger,Eirini K., Argyri, Justin K. Mogilski, Moss Herberholz, Julie Barron, Jacob S. Aday & Kevin F. Boehnke

  3. Servetus says:

    Cannabis given to Australian patients who do not respond to conventional medical treatments resulted in health related improvements:

    2-Apr-2025 — Patients prescribed medicinal cannabis in Australia maintained improvements in overall health-related quality of life (HRQL), fatigue, and sleep disturbance across a one-year period…Anxiety, depression, insomnia, and pain also improved over time for those with corresponding health conditions. […]

    In 2016, advocacy groups lobbied the Australian government to bring about legislation changes that allow patients who were not responding to conventional treatment to access medicinal cannabis with a prescription from clinicians. More than one million new patients in Australia have received medicinal cannabis prescriptions for more than 200 health conditions. […]

    [Research] Participants with clinician-diagnosed conditions completed questionnaires covering condition-specific symptoms, and HRQL, which encompasses physical, emotional, social, and cognitive function, as well as bodily discomfort.

    People with chronic health conditions reported improvements in fatigue, pain, and sleep. Patients with anxiety, depression, insomnia, or chronic pain diagnoses also showed improvements in condition-specific symptoms over 12 months. Patients treated for generalized anxiety, chronic pain, insomnia, and PTSD all showed improvements in HRQL. Participants with movement disorders had improved HRQL but no significant improvements in upper extremity function scores. […]

    “This is promising news for patients who are not responding to conventional medicines for these conditions.” […]

    AAAS Public Science News Release: Medicinal cannabis is linked to long-term benefits in health-related quality of life–Patients prescribed medicinal cannabis report less fatigue and sleep disturbance over 12 months

    PLOS One — Improvements in health-related quality of life are maintained long-term in patients prescribed medicinal cannabis in Australia: The QUEST Initiative 12-month follow-up observational study

    Margaret-Ann Tait, Daniel S. J. Costa, Rachel Campbell, Leon N. Warne, Richard Norman, Stephan Schug, Claudia Rutherford.

  4. Servetus says:

    The ACP weighs in on cannabis:

    4-Apr-2025 — The American College of Physicians (ACP) has issued Best Practice Advice for clinicians whose patients are considering or using cannabis or cannabinoids for management of chronic, noncancer pain. Cannabis or Cannabinoids for the Management of Chronic Noncancer Pain: Best Practice Advice From the American College of Physicians, was published today in Annals of Internal Medicine. […]

    In its Best Practice Advice ACP says clinicians should:

    Counsel patients about the benefits and harms of cannabis or cannabinoids when patients are considering whether to start or continue to use cannabis or cannabinoids to manage their chronic noncancer pain.

    Counsel the following subgroups of patients that the harms of cannabis or cannabinoid use for chronic noncancer pain are likely to outweigh the benefits:

    Young adult and adolescent patients

    Patients with current or past substance use disorders

    Patients with serious mental illness

    Frail patients and those at risk of falling

    Advise against starting or continuing to use cannabis or cannabinoids to manage chronic noncancer pain in patients who are pregnant or breastfeeding or actively trying to conceive.

    Advise patients against the use of inhaled cannabis to manage chronic noncancer pain.

    “This Best Practice Advice is important for practicing physicians when counseling our patients on the potential use of cannabis and cannabinoids to treat their chronic noncancer pain,” said Isaac O. Opole, President, ACP. “As the use of cannabis for medicinal purposes grows it’s critical to open that dialogue and review the emerging evidence related to benefits and harms. We need to raise awareness and get the word out to ensure that patients have the information they need to make informed decisions.”

    ACP has also published a position paper where it recommends a public health approach to address the legal, medical, and social complexities of cannabis use. […]

    Recommendations

    1. ACP supports rigorous research into the effects of legalizing cannabis on its use (including prevalence, frequency, and intensity of use) among older adults, adults, adolescents, and children; prevalence of cannabis use disorder and other behavioral health conditions; motor vehicle injuries and impaired driving; poisonings; and other adverse outcomes.

    2. ACP recommends that possession of small amounts of cannabis for personal use be decriminalized. ACP calls on policymakers to take an evidence-informed approach when considering amending the legal status of cannabis.

    3. ACP supports an evidence-based public health approach to addressing cannabis and hemp-derived products (including low-tetrahydrocannabinol cannabidiol and Δ-8-tetrahydrocannabinol products) in jurisdictions where they are legal, with a focus on prohibiting access to minors and preventing unsafe use among adults.

    4. ACP supports sufficient resources for cannabis-related public health activities, oversight, and regulation. The U.S. Food and Drug Administration and other federal, state, local, and tribal agencies should receive necessary resources to regulate cannabis products.

    5. ACP supports comprehensive insurance coverage of evidence-based treatments of cannabis use disorder.

    6. ACP supports the development of evidence-based medical education on the health effects of cannabis and cannabinoids. Cannabis content should be incorporated into substance use curricula at all levels of physician education.

    7. ACP supports programs and funding for rigorous scientific evaluation of the potential therapeutic benefits of cannabis and cannabinoids.

    8. ACP reiterates its strong support for exemption from federal criminal prosecution; civil liability; or professional sanctioning, such as loss of licensure or credentialing, for physicians who recommend, prescribe, or dispense cannabis in accordance with state law.

    Conclusion: ACP strongly recommends adoption of policies to increase understanding of the effects of legalizing cannabis for medical and recreational use. A robust public health approach to controlling cannabis should be implemented in states where it is legal, with attention toward prohibiting use among young people and preventing unsafe use among adults. Educational resources should be made available to physicians so they can provide accurate information about the health effects of cannabis and care for patients with cannabis use disorder. Extensive research into the health effects of cannabis use must be done, including on potential harms when used by older adults and more medically complex populations. Finally, to address the disproportionate effects of aggressive drug control policies on marginalized racial and ethnic populations, ACP calls for the decriminalization of possession of small amounts of cannabis for personal use.

    AAAS Public Science News Release: ACP’s Best Practice Advice addresses use of cannabis, cannabinoids for chronic noncancer pain

    Authors: Ryan Crowley, BSJ, Katelan Cline, BA, David Hilden, MD, MPH, and Micah Beachy, DO, for the Health and Public Policy Committee of the American College of Physicians.

  5. Servetus says:

    CBD reduces autism (ASD) symptoms in children:

    8-Apr-2025 – New research presented at the 2025 European Congress of Psychiatry reveals that the use of cannabidiol (CBD) cannabis extract can lead to meaningful benefits and improve the behaviour of children and adolescents with autism spectrum disorder (ASD). ASD affects approximately 1 in 100 children around the world and symptoms can include difficulty interpreting language, difficulty expressing emotions, and repetitive behaviour and routines.

    The meta-analysis included randomised, placebo-controlled trials on the efficacy or safety of CBD cannabis extracts in children and adolescents with ASD. Three studies were used in total with 276 participants with a mean age of 10.5, ranging in age from 5 to 21. The dosage of CBD cannabis extract started at 1 mg/kg per day and was titrated up to 10 mg/kg. […]

    Key Findings Include:

    CBD cannabis extract use shows moderate improvements in social responsiveness and small yet notable reductions in disruptive behaviours.

    CBD cannabis extract significantly enhanced social responsiveness and reduced disruptive behaviour.

    The use of CBD cannabis extract has a favourable safety profile as it did not increase adverse events compared to placebo.

    There were no significant differences between adverse events in CBD cannabis extract versus placebo. […]

    Professor Geert Dom, EPA President, said: “ASD can be extremely frustrating for all involved; parents of children and adolescents with the disorder, the treating clinicians and of course the children and adolescents themselves. A large part of this frustration is down to finding a viable treatment option that works to reduce symptoms. It is with delight that we see the results of this meta-analysis and we hope to see further research into this so we can move towards a solution to the unmet need within this community”. […]

    AAAS Public Science News Release: Cannabidiol therapy could reduce symptoms in autistic children and teenagers

    • Servetus says:

      Speaking of autism and what causes it:

      21-Apr-2025 – Scientists from The Hospital for Sick Children (SickKids) and University of Nevada Las Vegas (UNLV) have uncovered a genetic link between autism spectrum disorder (ASD) and a rare genetic condition called myotonic dystrophy type 1 (DM1). The study, published today in Nature Neuroscience, suggests that while ASD has previously been characterized by a loss of gene function, another mechanism may be leading to the social behaviours often observed in individuals with ASD. […]

      TREs occur when sections of a DNA strand are repeated two or more times, and the likelihood of those repeats causing errors in gene function increases each time.

      In 2020 Yuen discovered that TREs are genetic contributors to autism, identifying more than 2,588 different places in the genome where TREs were much more prevalent in people with ASD. Similarly, people with DM1 have a TRE in the DMPK gene.

      “A variation really stood out to me that we see in rare neuromuscular disease,” says Dr. Łukasz Sznajder, a research lead and Assistant Professor at UNLV. “This is how we started connecting the dots. We found a molecular link, or overlap, which we believe is the core of causing autistic symptoms in children with myotonic dystrophy.” […]

      As the tandem repeat expands in the DMPK gene, the research team, including collaborators at the University of Florida and Adam Mickiewicz University (Poland), found its altered RNA binds to a protein that is involved in gene splicing regulation during brain development. This so-called “toxic RNA” depletes the protein and prevents it from binding to other RNA molecules in important areas of the genome, causing a protein imbalance which results in mis-splicing other genes.

      “TREs are like a sponge that absorbs all these important proteins from the genome. Without this protein, other areas of the genome don’t function properly,” explains Yuen.

      The Yuen Lab and Sznajder Lab are already exploring whether this mis-splicing is happening in other genes associated with ASD, as well as how their findings could inform precision therapies that release these proteins back into the genome. […]

      DM1 is an inherited condition which causes progressive muscle loss and weakness. While ASD is present in around one per cent of the general population, it is 14 times more likely to develop in people with DM1.

      The study revealed that the genetic variation that causes DM1 — tandem repeat expansions (TREs) in the DMPK gene — also impacts brain development. The research team found that the effects of TREs interfere with a critical process called gene splicing, which is essential for gene function. The disruption causes a protein imbalance that can result in mis-splicing of multiple genes involved in brain function, and may explain why some of the social and behavioural outcomes of ASD develop in people with DM1.

      “Our findings represent a new way to characterize the genetic development of autism,” explains Dr. Ryan Yuen, Senior Scientist in the Genetics & Genome Biology program at SickKids. “By identifying the molecular pathway behind this connection, we can begin to investigate new approaches to ASD diagnosis and the development of precision therapies that release these proteins back into the genome.” […]

      This study was funded by the Azrieli Foundation, the National Institutes of Health (NIH), Myotonic Dystrophy Foundation, Muscular Dystrophy Association, the UNVL startup fund, the University of Florida Centre for Autism and Neurodevelopment, the National Science Centre, Poland, SickKids Research Institute, Brain Canada, the Government of Ontario, the University of Toronto McLaughlin Centre, the Canadian Institutes of Health Research (CIHR), The Petroff Family Foundation, Tribute Communities, The Marigold Foundation and SickKids Foundation.

      AAAS Public Science News Release:
      Study reveals new genetic mechanism behind autism development

      Nature Neuroscience: Autism-related traits in myotonic dystrophy type 1 model mice are due to MBNL sequestration and RNA mis-splicing of autism-risk genes

  6. Servetus says:

    A functional wiring diagram of the brain has been revealed that will aid in future brain research focusing on brain pathways related to addiction.

    09-APR-2025 — From a tiny sample of tissue no larger than a grain of sand, scientists have come within reach of a goal once thought unattainable: building a complete functional wiring diagram of a portion of the brain. In 1979, famed molecular biologist, Francis Crick, stated that it would be “[impossible] to create an exact wiring diagram for a cubic millimeter of brain tissue and the way all its neurons are firing.” But during the last seven years, a global team of more than 150 neuroscientists and researchers has brought that closer to reality.

    The Machine Intelligence from Cortical Networks (MICrONS) Project has built the most detailed wiring diagram of a mammalian brain to date. Today, scientists published the scientific findings from this massive data resource in a collection of ten studies in the Nature family of journals. The wiring diagram and its data, freely available through the MICrONS Explorer, are 1.6 petabytes in size (equivalent to 22 years of non-stop HD video), and offer never-before-seen insight into brain function and organization of the visual system. […]

    “IARPA’s moonshot investment in the MICrONS program has shattered previous technological limitations, creating the first platform to study the relationship between neural structure and function at scales necessary to understand intelligence. This achievement validates our focused research approach and sets the stage for future scaling to the whole brain level.”

    Scientists at Baylor College of Medicine began by using specialized microscopes to record the brain activity from a one cubic millimeter portion of a mouse’s visual cortex as the animal watched various movies and YouTube clips. Afterwards, Allen Institute researchers took that same cubic millimeter of the brain and sliced it into more than 25,000 layers, each 1/400th the width of a human hair, and used an array of electron microscopes to take high-resolution pictures of each slice. Finally, another team at Princeton University used artificial intelligence and machine learning to reconstruct the cells and connections into a 3D volume. Combined with the recordings of brain activity, the result is the largest wiring diagram and functional map of the brain to date, containing more than 200,000 cells, four kilometers of axons (the branches that reach out to other cells) and 523 million synapses (the connection points between cells).

    “Inside that tiny speck is an entire architecture like an exquisite forest,” said Clay Reid, Ph.D., senior investigator and one of the early founders of electron microscopy connectomics who brought this area of science to the Allen Institute 13 years ago. “It has all sorts of rules of connections that we knew from various parts of neuroscience, and within the reconstruction itself, we can test the old theories and hope to find new things that no one has ever seen before.” […]

    ScienceDaily: Scientists complete largest wiring diagram and functional map of the brain to date: The MICrONS Project is considered the most complicated neuroscience experiment ever attempted

    Nature Portfolio: The MICrONS Project

  7. NorCalNative says:

    From the paper:…For many patients, evidence suggests that the known harms of cannabis outweigh the (potentially small degree of benefit to ease chonic noncancer pain.)…

    My experience has been different. I benefit from daily cannabis use for chronic noncancer pain. So much so that I was able to replace 5 prescriptions (polypharmacy) with cannabis.

    Morphine, gabapentin, ibuprofen, soma, and a tricyclic antidepressant Elavil.

    Here’s an AI overview: Polypharmacy, or taking multiple medications at once carries significant risks including increased adverse drug reactions, cognitive impairment, falls, and even mortality. — These dangers are amplified in older adults and individuals with multiple chronic conditions.

    The cannabis harms pale in comparison to polypharmacy. Everyone has different results with medicine and perhaps I’m just lucky to be prescription-free for the last 11 years thanks to cannabis.

    The paper talks about harm from addiction and harm from impairment. Both legitimate concerns. However, my cannabis use has remined steady for decades. I use 1/2-to-3/4 of a gram per day. I’m not worried about addiction. In regard to impairment in driving? I’m totally fine to drive after a few tokes. The one time I wasn’t several years ago I simply stayed home.

    I’m a highly-educated cannabis consumer and my benefits are real. If this wasn’t the case I’d still be taking prescriptions and doing polypharmacy. Cannabis reduces suffering better than prescriptions.

    Not having to wait on oral medicine is a huge bonus for osteoarthritis and/or neuropathy.

    So, if you can, rule-out cannabis before prescriptions if your conditions permit it. Things like diabetes and cardiac issues are best served with prescription medications.

    But, if your issues are arthritis or neuropathy? Weed might be the best chioce.

  8. Servetus says:

    Psychedelic control of the fear response examined:

    23-Apr-2025 — “Our study underscores how psychedelics can do more than just change perception; they can help dial down inflammation and reset brain-immune interactions,” said corresponding author Michael Wheeler, PhD, of the Gene Lay Institute of Immunology and Inflammation as well as the Ann Romney Center for Neurologic Diseases at Brigham and Women’s Hospital (BWH), a founding member of the Mass General Brigham healthcare system. “This could reshape how we think about treatment for inflammatory disorders and conditions like anxiety and depression.”

    Prior research has shown immune signaling can drive the development of neuropsychiatric diseases such as major depressive disorder (MDD). However, the ways that specific immune mechanisms can also affect behaviors due to chronic stress or MDD remained unclear.

    Using a mouse model of chronic stress, the researchers determined that increased crosstalk between cells in the amygdala, or the brain’s fear center, boosted fear behaviors, elevated inflammatory signaling, and activated fear-promoting amygdala neurons.

    Furthermore, inflammatory immune cells called monocytes migrated from other parts of the body to the brain meninges during chronic stress. The research team demonstrated that artificially manipulating these cells impacted fear behaviors. Treating stressed mice with psilocybin and MDMA prevented monocytes from accumulating in the brain and lowered fear behaviors. […]

    Next steps include examining the long-term effects of psychedelic treatment on patients with MDD or inflammatory diseases. Wheeler is currently collaborating with investigators from the Massachusetts General Hospital Center for the Neuroscience of Psychedelics on a clinical trial of patients with depression who are being treated with psychedelics and will examine their tissue samples. […]

    AAAS Public Science News Release: Study finds psychedelics can reverse neuroimmune interactions that boost fear – Mass General Brigham researchers found that interactions between immune and brain cells drive fear responses, but treatment with psychedelics like MDMA and psilocybin may reverse these effects

    Nature: Psychedelic control of neuroimmune interactions governing fear

    Authors: Elizabeth N. Chung, Jinsu Lee, Carolina M. Polonio, Joshua Choi, Camilo Faust Akl, Michael Kilian, Wiebke M. Weiß, Georgia Gunner, Mingyu Ye, Tae Hyun Heo, Sienna S. Drake, Liu Yang, Catarina R.G.L. d’Eca, Joon-Hyuk Lee, Liwen Deng, Daniel Farrenkopf, Anton M. Schüle, Hong-Gyun Lee, Oreoluwa Afolabi, Sharmin Ghaznavi, Stelios M. Smirnakis, Isaac M. Chiu, Vijay K. Kuchroo, and Francisco J. Quintana.

  9. Servetus says:

    A single psilocybin treatment lasts for weeks:

    22-Apr-2025 – In a groundbreaking research study, University of Michigan researchers have discovered that a single dose of a psychedelic compound can enhance cognitive flexibility—the brain’s ability to adapt to changing circumstances—for weeks after administration, potentially revolutionizing treatments for depression, PTSD, and neurodegenerative diseases.

    The study, published today in the journal Psychedelics, demonstrates that mice treated with a single dose of 25CN-NBOH, a selective serotonin 2A receptor agonist, showed markedly improved performance in reversal learning tasks compared to control groups when tested 2-3 weeks after treatment.

    “What makes this discovery particularly significant is the sustained duration of cognitive benefits following just one psychedelic dose,” explains Professor Omar J. Ahmed, the study’s senior, corresponding author from the University of Michigan’s Department of Psychology. “We observed enhanced learning adaptability that persisted for weeks, suggesting these compounds may induce lasting and behaviorally meaningful neuroplasticity changes in the prefrontal cortex.”

    Using an innovative automated sequential learning paradigm, researchers measured how effectively mice could adapt to rule reversals—a standard test for cognitive flexibility. The psychedelic-treated mice demonstrated superior adaptability compared to saline controls, with enhanced task efficiency, higher percentages of correct trials, and increased reward acquisition during the reversal phase.

    The results complement existing cellular research showing psychedelic-induced structural remodeling in the prefrontal cortex but uniquely demonstrate sustained cognitive benefits persisting long after the immediate effects of the drug have dissipated. […]

    The study’s automated behavioral task represents a significant methodological advance for evaluating flexible learning, enabling researchers to efficiently evaluate cognitive flexibility in future investigations of psychedelic compounds. This high-throughput approach could accelerate the development of targeted psychedelic therapies for specific cognitive deficits. […]

    AAAS Public Science News Release: Single-dose psychedelic boosts brain flexibility for weeks, peer-reviewed study finds — Groundbreaking research reveals potential for psychedelic compounds to enhance cognitive agility in neuropsychiatric treatment

    Genomic Press: Psychedelics — Single-dose psychedelic enhances cognitive flexibility and reversal learning in mice weeks after administration

    Authors: Elizabeth J. Brouns, Tyler G. Elkins, Omar J Ahmed.

  10. Servetus says:

    Latent psychotic disorders (HPPD) associated with psychedelics are investigated in research volunteers in London and San Francisco:

    22-Apr-2025 — …the side-effect profile [of psychedelic drugs] is still incompletely understood. In particular, the use of psychedelics has been posited to carry a risk of triggering latent psychotic disorders or persistent visual hallucination, known as Hallucinogen Persisting Perception Disorder (HPPD). In order to better understand the prevalence and risk factors of such side-effects, Katie Zhou and colleagues surveyed 654 people online who were planning to take psychedelics through their own initiative. Of those, 315 people were resurveyed two weeks after their experience and 212 people were resurveyed again four weeks after their experience. The sample was 74% male, and 77% university educated. […]

    About one third had been diagnosed with at least one psychiatric condition. The authors found a weak correlation between lifetime psychedelic use and both delusional ideation and magical thinking. However, on average, delusional ideation was slightly reduced one month after psychedelic use. These results suggest that schizotypal traits may not be caused by taking LSD or magic mushrooms, in keeping with the principle that correlation does not imply causation. About a third of individuals surveyed at the four-week mark did have some lingering hallucinatory sensory experiences, such as intensified colors and afterimages. However, the majority of those who experienced this did not report being distressed by it. The strongest predictors of persistent visual aftereffects were the personality trait absorption—the tendency to be easily immersed in sensory or imaginative experiences—and younger age. This corroborates previous findings showing that young people and adolescents may be at a particular risk of HPPD. […]

    According to the authors, empirical scrutiny of the potential risks of psychedelics should accompany changes in policy and access to psychedelic drugs. […]

    AAAS Public Science News Release: Predicting long-term psychedelic side-effects — Schizotypal traits may not be caused by taking LSD or magic mushrooms

    PNAS Nexus: Prediction of hallucinogen persisting perception disorder and thought disturbance symptoms following psychedelic use

    Authors: Katie Zhou, David de Wied, Robin L Carhart-Harris, Hannes Kettner.

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