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How psychedelics work

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How psychedelics work
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Psychedelics, also known as hallucinogens, are a class of psychoactive substances that alter perception, mood and cognitive processes. They work by interacting with specific receptors in the brain and altering the way that the brain processes information.

Classic psychedelics work by activating the serotonin receptors in the brain. Serotonin has a wide variety of functions in the human body including cognition, perception, emotions, appetite and digestion. 

People sometimes call it the “happy” chemical because it contributes to well-being, mood and happiness. 

The scientific name for serotonin is 5-hydroxytryptamine (5-HT). It is a neurotransmitter, meaning that the body uses serotonin to send messages between brain cells. 

See also  What is ketamine therapy?

One of the primary ways that psychedelics work is by activating serotonin receptors in the brain, particularly the serotonin 2A receptor (5-HT2A). Activation of the 5-HT2A receptor by psychedelics can result in changes in activity of serotonin and other neurotransmitters, such as dopamine and norepinephrine, which can contribute to the drug’s effects.

The 5-HT2A receptor and the binding of classic psychedelics to it are well studied, which allows chemists to model the relationships between the activity caused by a psychedelic and its structure. Recent efforts have been made to use computational modeling to engineer psychedelic-based therapeutics to increase the diversity of psychedelic compounds and also to engineer compounds that lack hallucinogenic effects, but maintain the therapeutic benefit.

The specific effects of psychedelics can vary widely depending on the chemical structure of the psychedelic, in addition to the dose and the individual’s unique brain chemistry. 

Level up your chemistry knowledge

All classic psychedelics have a similar chemical structure, we call this a chemical scaffold or a pharmacophore. A pharmacophore is like a key. Just as a key is specifically shaped to fit into a particular lock, a pharmacophore is specifically shaped to fit into a biological target, like the 5-HT2A receptor. 

In the figure below, you can see that the basic pharmacophore is a 6-pointed ring with a small chemical “arm” on the right. The pharmacophore is basically a skeleton key that can bind and activate the 5-HT2A receptor, and then the additional chemical groups that make each psychedelic unique can dictate the potency of the drug, duration of the psychedelic experience and types of hallucinogenic effects. 

See also  What we know about the effect of psychedelics on women’s health

Differences in this basic pharmacophore divide psychedelics into two broad families, tryptamines on the left side of the figure and phenethylamines on the right side. The conversed pharmacophore is highlighted in each psychedelic structure in the figure.

The chemical structures of psychedelics – note how the chemical structures are conserved within the two families.

Potency and other drug effects are modulated by how each psychedelic binds to the 5-HT2A receptor. Each of these different psychedelics is a different key, and they all fit into the same lock. 

However, some keys fit perfectly into locks (like serotonin into its receptor). Other keys almost fit a lock, or a key might force its way into a lock and get stuck for a while. The length of time the key is in the lock and/or how tight the key/lock fit is can lead to different psychedelic experiences.

Chemical isomers

Keys can look almost identical and fit different locks. Similarly, chemical molecules called isomers can have almost the exact same chemical structure but they differ only in the position of a chemical group, which can result in different psychedelic effects.

For example, psilocin and bufotenin are both psychedelics with nearly identical chemical structures. The only thing that is different is where the alcohol (-OH) chemical group is located on the aromatic ring. The result is very different hallucinogenic effects.

How psychedelics work

The chemical structures of Bufo and Psilocin are exactly the same, except the -OH group is in different places on the 6-pointed ring.

Psilocybin is a naturally occurring psychedelic substance found in certain types of mushrooms. When consumed, it is converted to psilocin in the body, which is thought to be responsible for its effects including altered states of consciousness, changes in perception and emotional changes. It can also cause visual and auditory hallucinations and alter the sense of time. 

Bufotenin, also called Bufo or “the toad”, is a naturally occurring psychedelic substance found in the skin of some toads and in certain plants. Bufotenin is known to produce effects similar to those of other psychedelics, including altered states of consciousness, changes in perception and emotional changes. However, its effects are generally less intense and shorter-lasting than those of other psychedelics, such as psilocybin or LSD. A typical Bufo trip is about 20 minutes long.

Even these short hallucinogenic trips can be very impactful. On a Joe Rogan episode, former heavyweight boxing champion Mike Tyson described his experience with Bufo and said it profoundly changed his life.

“I look at life differently, I look at people differently. It’s almost like dying and being reborn… It’s inconceivable. I tried to explain it to some people, to my wife, I don’t have the words to explain it. It’s almost like you’re dying, you’re submissive, you’re humble, you’re vulnerable — but you’re invincible still in all.”

Stereochemistry

Furthermore, psychedelic chemicals are very complex. Just like a key, chemical molecules are 3-dimensional, and chemists call this stereochemistry. They can exist as mirror images of each other, like your right and left hands. Chemists call this chirality, and the mirror images are referred to as R- and S-enantiomers.

A mixture of the R and S enantiomers is called a racemic mixture, and the individual R or S enantiomer can be isolated to a pure substance of just one enantiomer. All three substances, the racemic, the R- and the S-enantiomer, can have different potency, psychedelic effects, or lack psychedelic effects. 

You may have heard about racemic mixtures in reference to the anesthetic drug ketamine. 

The R and S enantiomers of Ketamine. Figure from Jelen, L.A et al. “Ketamine: A tale of two enantiomers” DOI:10.1177/0269881120959644

The racemic mixture of ketamine is a mixture of the two mirror images of the molecule, and it is typically used as an anesthetic and is known to produce a range of effects, including dissociation (a feeling of disconnection from one’s body and surroundings), hallucinations, and altered states of consciousness.

“Esketamine” is the isolated S-enantiomer of ketamine, meaning scientists isolated one of the mirror-image chemicals of ketamine. Additionally, Esketamine is the pharmaceutical trade name of a nasal spray that has been approved by the US Food and Drug Administration (FDA) for the treatment of treatment-resistant depression in adults in combination with an oral antidepressant. It is thought to produce its antidepressant effects by inhibiting the action of a neurotransmitter called glutamate in a specific region of the brain called the prefrontal cortex. 

Ketamine is not a classic psychedelic and acts primarily on the NMDA (N-methyl-D-Aspartate) receptor, rather than the 5-HT2A receptor.

Psychedelic effects

Now that you’re a chemistry expert, you know that tryptamines and phenethylamines have similar chemical structures to serotonin (5-HT), which explains why they bind the serotonin receptor. However, these chemicals produce different pharmacological effects than our naturally occurring serotonin.

Serotonin can influence learning, memory, happiness as well as regulating body temperature, sleep, sexual behavior and hunger. While psychedelics can produce a range of psychological effects, including altered states of consciousness, altered perception, and changes in mood and thought.

Most psychedelics bind the 5-HT2A receptor, however, that is not the only serotonin receptor. There are 14 distinct 5-HT receptors in humans, and some psychedelics, like LSD, bind most of the 14 receptors. In addition, some psychedelics will bind other neurotransmitter receptors, like the dopamine receptors. It is currently not known which of the receptors mediate the potential therapeutic actions of psychedelics, and recent studies suggest 5-HT2A is not acting alone.

Remember how the receptors act as a lock, and the psychedelics act as a key. When the psychedelic binds the receptor, it can hold the lock in an activated (unlocked) or deactivated (locked) state. The serotonin receptor acts like a dam that controls the flow of ions from outside of a brain cell (a neuron) to the inside. When the receptor is activated by a psychedelic and unlocks the dam, this leads to a flow of ions into the neuron which excites the cell and changes its usual activity.

This flow of ions in neurons in the frontal cortex of the brain, are thought to increase dendritic excitability. Dendrites are the branches of neuron cells, and psychedelics have been shown to promote the formation of new dendritic spines – called promoting neuroplasticity. Neuroplasticity is a way for the brain to rewire itself. Neuroplasticity can promote learning, development and forming new memories. 

It has been demonstrated in lab-grown neuron cells that the dendritic spine size, density, and number of dendrites on each cell increased after psychedelic treatment. In another study with psilocybin, the dendritic spine density remained elevated up to 1 month after the initial administration of psilocybin.

Visual hallucinations are believed to occur in the primary visual cortex of the brain. It has been found that neuronal firing decreases in response to LSD. However little else is known. 

Not only are visual hallucinations a mystery to scientists. It is also not understood how behavioral changes are linked to the biological action of psychedelics. Understanding this link would be beneficial to identifying which individuals are more likely to respond positively to psychedelic therapies.

This article was first published in Nina’s Notes on 28 December and is republished on Psychedelic Health with permission.

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Public Support for Psilocybin in the US Mirrors Early Days of Cannabis Legalisation

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A study from the RAND Corporation has revealed a significant gap between the growing political momentum for psychedelic reform and actual US public opinion. While states like Oregon and Colorado have already moved toward regulated access, the majority of the American public remains cautious, particularly regarding synthetic substances like MDMA and LSD.

Psilocybin, The Preferred Choice

The 2025 RAND Psychedelics Survey found that psilocybin, often referred to as “magic mushrooms,” enjoys the highest level of support among psychedelics, with 23.1% of US adults backing its legalisation.

Interestingly, researchers noted that current support for psilocybin mirrors the public sentiment for cannabis in the mid-1990s, which was the period immediately preceding the first wave of state-level medical marijuana laws. For context, support for legal cannabis today stands at 64.6%. Whether psilocybin will follow this same exponential trajectory toward mainstream acceptance remains a central question for the psychedelics space.

Ambivalence Towards MDMA and LSD

Despite high-profile clinical trials and FDA-track research, synthetic psychedelics and empathogens face a much steeper climb in the face of public opinion.

Only 9.2% of respondents said they support MDMA for legal use. Support for LSD sits slightly higher at 9.9%, and more than three-quarters of Americans believe that both MDMA and LSD should remain illegal.

The report suggests that the public differentiates between “natural” and “synthetic” substances, showing a positive bias towards fungi-based medicines against lab-synthesised compounds.

Medical-First

The study highlights that support is not “all or nothing.” Even among those who oppose broad legalisation, there is significant support for therapeutic use.

Addressing mental or physical health conditions was the most cited reason for allowing legal access across all three substances: psilocybin (29.7%), LSD (22.7%), and MDMA (18.4%).

Respondents also showed support for taking psychedelics in a supervised setting. When asked how adults should access these medicines, the most endorsed model was at a medical facility under professional supervision (48.5% for psilocybin).

The Experience Gap

Personal experience remains a powerful driver of opinion. Among individuals who have actually used psilocybin, support for legalisation jumps to 61.6%. This follows the trend seen in the cannabis sector, where 80% of lifetime users support its legal status.

As the UK and Europe look to the US for regulatory cues, these data serve as a sobering reminder: while the “psychedelic renaissance” is well-underway in research labs and state legislatures, winning over the general public will require a sustained focus on medical safety and controlled environments, as well as clear communication on mainstream channels.

The RAND Corporation is a non-profit, non-partisan policy think tank known for its strict peer-review processes and a history of informing complex national security and health policies.

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Op-ed: In Psychedelic Medicine, Patient Experience Data Will Separate the Winners from the Rest

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This article was written by Dr. Jenya Antonova, head of Compass Strategy and Research Inc., as part of Psychedelic Health’s op-ed program. To submit article ideas, please email news@psychedelichealth.co.uk

The psychedelic sector stands at a critical point. Clinical trials suggest meaningful benefits in depressive, anxiety-, trauma-related, and substance use disorders—conditions marked by substantial morbidity, diminished quality of life, and impaired social and occupational functioning.

Psychedelic treatments aim to improve not only symptoms, but how people think, feel, relate, and function in the world. In other words, they aim to improve health in its fullest sense. Public narratives speak of great potential. Investors anticipate scale.

Yet effective long-term integration into healthcare systems will be driven not by enthusiasm or early efficacy signals alone. For that, psychedelic therapies must demonstrate measurable safety and improvements in health in a way that satisfies regulators, health technology assessment bodies, policymakers, clinicians, and patients.

Health is a very complex construct. It is lived and experienced by each of us uniquely. And that lived experience must be measured. This is not merely a philosophical argument—it encapsulates the methodological and practical aspects of how lived experiences are measured in clinical trials.

In some therapeutic areas, like oncology, infectious diseases, diabetes, and endocrine autoimmune conditions, objective laboratory values, imaging, or physiological assessments can assess treatment response. In contrast, depressive, anxiety-, trauma-related, and substance-use disorders lack validated objective endpoints that confirm recovery.

Therefore, the assessment of risks and benefits of psychedelic medicine will ultimately rest on how convincingly it translates subjective assessment of well-being into rigorous patient experience data that matter to all stakeholders. 

However, different stakeholders interpret patient experience data through different lenses.

Assessing Effects: Clinically Meaningful vs. Statistically Significant 

Regulators determine whether substantial evidence of effectiveness and acceptable safety warrant authorization for use in humans. In the United States, the FDA’s Patient-Focused Drug Development framework makes clear that clinical outcome assessments used to support labeling claims must capture outcomes that are meaningful to patients—specifically how patients feel and function.

The instrument for clinical outcome assessment must be fit for purpose, with demonstrated validity, reliability, and responsiveness in the target population. In Europe, the EMA reflection paper on the use of health-related quality-of-life measures in the evaluation of medicinal products underscores that patient-reported outcomes must be methodologically sound and clinically interpretable to inform regulatory decision-making. Beyond reliability and validity, scoring must be clearly interpretable to ensure that demonstrated effects are clinically meaningful, not merely statistically significant.

Historically, regulatory objectives around patient experience data have centered on labeling. Yet comprehensive patient experience data can also enhance the evidentiary robustness of the entire submission. It includes evidence of holistic treatment effects, psychiatric safety, durability of benefit, the potential influence of functional unblinding and expectation bias—considerations that featured prominently in the FDA’s 2024 review of MDMA-assisted therapy for PTSD.

From Approval to Rollout and Patient Uptake

Once regulatory approval is granted, the next critical milestone is reimbursement. The health technology assessment (HTA) agencies worldwide place significant weight on patient experience data, though their approaches vary.

The German AMNOG legislation and the EU Joint Clinical Assessment framework require patient-relevant outcomes, including morbidity and health-related quality of life. Other agencies such as TLV (Sweden), ZIN (the Netherlands), NoMA (Norway), SMC (Scotland), NCPE (Ireland), HAS (France), and NICE (the UK) evaluate patient experience data within their clinical or economic appraisals.

Health-utility estimates used in cost-utility analyses are typically derived from patient experience data. All HTA bodies demand that patient experience data be of high methodological rigor, consistent with standards established by regulatory agencies. 

Along with the HTA agencies, policy makers will decide whether psychedelic medicine remains niche and tightly constrained, or becomes responsibly integrated into mainstream care. Their decisions will hinge on whether the field can provide rigorous evidence of long-term safety, durability of effect, real-world functional recovery, and abuse potential—areas for which long-term patient experience data will be critical.

Approval, however, does not guarantee wide uptake. Ultimately, patients decide whether to pursue a therapy. Patients want to understand not only “Does it work?” but also “What will it feel like? How will it change my daily life? What challenges might I face?” 

Here, credible data on direct lived experiences can replace anecdote and media narratives, enabling patients to make well-informed decisions grounded in what matters to them most.

Clinicians bridge the gap between clinical trial data and the patient taking the treatment. In psychedelic medicine, they not only prescribe treatments, determine dosing, but also facilitate and monitor sessions, advise patients, and monitor the effect of treatment. Rigorous patient experience data enables clinicians to merge evidence-based decision-making with a patient-centered approach.

Understanding Patient Experience Data

How, then, can patient experience data be demonstrated in practice?

The most common and most influential approach is for Phase 3 to generate evidence-based instruments for clinical outcome assessment, which include clinician-reported outcomes, and patient-reported outcomes. These instruments can—and often do—support primary, secondary, or exploratory endpoints rendering completeness to the risk-benefit assessment. 

Qualitative research offers a scientific framework for systematically capturing patients’ lived experiences. Qualitative evidence is a must for establishing content validity of instruments for patient-reported outcomes and clinician-reported outcomes that support clinical trial endpoints. 

In-trial interviews can take clinical trial data to the next level: contextualize quantitative findings, deepen understanding of patient experience with the treatment, and generate critical evidence for the interpretation of treatment effect. In psychedelic medicine, qualitative insights can be particularly powerful when systematically collected and analyzed.

Patient preference research represents another powerful tool. Preference studies can quantify how patients weigh different treatment attributes—safety, efficacy, overall treatment experience, and long-term outcomes. Understanding of patient trade-offs can inform regulatory, reimbursement, policy decision-making and clinical counseling.

What does it all mean for the strategy?

The central lesson we have learned from other therapeutic areas, which applies acutely to psychedelics, is that patient experience data must be intentional. It requires early planning, validated instruments, clear endpoint hierarchies, and alignment with regulatory and HTA expectations.

The lack of comprehensive patient experience data can inhibit regulatory and HTA reviews and result in suboptimal access outcomes. Yet launching patient experience data strategy at Phase 3 is likely too late.

Phase 3 are confirmatory trials. By then, the instruments must be validated, endpoints pre-specified, statistical power estimated, and clinically meaningful change established. If these decisions are not pre-determined, Phase 3 carries avoidable risks that are costly and highly visible.

Phase 2 should therefore serve a dual purpose: to explore efficacy and to establish the patient experience data framework. This includes validating clinical outcome assessments, testing their performance in the target population, and defining thresholds for meaningful change that can be carried forward into confirmatory trials. Therefore, sponsors should start planning patient experience data strategy very early. 

For investors, an early patient experience data strategy can signal strategic maturity, foresight into the future regulatory and HTA requirements, and understanding of what will drive the value in a field subjected to intense public scrutiny and regulatory attention. 

As psychedelic therapies confront heightened scrutiny, they must show their ability to transform patient lives and improve their functioning in society. For that, rigorous patient experience data is not optional. It is a winning card.

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How the Medical Psychedelics Working Group is Moving the Needle on UK Drug Policy

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One of Britain’s central think tanks for drug policy reform is looking for new partners to join forces in 2026.

Over its five-year history, the group has achieved major milestones, which include consulting with the UK Home Office on a recent call for submissions on barriers to research scheduled substances.

In July 2025 the UK government responded to recommendations by the Advisory Council on the Misuse of Drugs on rescheduling psychedelics for clinical research, agreeing in principle to ease licensing for universities and hospitals and exempt approved clinical trials from Home Office licences.

“I like to think we swayed them with our evidence”, said James Bunn, Head of Operations at Drug Science, the organisation overseeing the group.

The group is currently on the lookout for new members and corporate partners.

“We’ve seen what collaboration can achieve with medical cannabis. Now it’s time to apply that same evidence-based, patient-led approach to psychedelics”, said Drug Science founder Professor David Nutt. 

What Is the Medical Psychedelics Working Group?

The Medical Psychedelics Working Group was established in 2020 in response to growing scientific evidence, shifting regulatory landscapes, and the persistent barriers facing legitimate psychedelic research. 

Following the legalisation of medical cannabis in the UK in 2018, a need emerged for coordinated, interdisciplinary action to ensure psychedelic medicines could be responsibly developed within public health systems.

Created to challenge decades of medical marginalisation, the group seeks to advance a rational and evidence-based approach to psychedelic research and clinical treatment. Its work focuses on generating robust scientific data, supporting regulatory reform, and improving understanding among policymakers, clinicians, researchers, and the wider public. 

Central to this mission is addressing the constraints imposed by Schedule 1 classification, which continues to limit research through cost, complexity, and delay.

“While the legislation did not preclude scientific research with these drugs, it made them significantly more difficult, time-consuming and costly to study”, said Bunn. “Drug Science’s Medical Psychedelics Working Group aims to change this situation for the better.”

Major Achievements and Upcoming Goals

Currently, the group is running an MDMA psychotherapy research trial in collaboration with University College London. The study aims to improve understanding of MDMA-assisted psychotherapy, focusing on how the psychotherapeutic component interacts with the drug’s effects. The project aims to clarify treatment mechanisms and enhance safety and efficacy.

Drug Science Head of Research, Dr. Anne Schlag, says the group is “continuously responding to the government’s call for evidence”.

This includes a recent response to a 2026 ketamine review by the Advisory Council on the Misuse of Drugs, which was commissioned last year to assess harms and legal classification. 

With funding by Norrsken Foundation, the group is running an MCDA (multi-criteria decision analysis) comparing treatments for treatment resistant depression, including psilocybin and ketamine. We can expect results for the analysis before July, says Schlag.

The group is also working closely together with Australian colleagues such as Prof Ranil Gunewardene, to understand, document and publish everything related to the developments in MDMA and psilocybin rescheduling in Australia.

“We hope [it] can serve as an example for the UK and Europe. A very exciting case series of the first fifteen MDMA patients is forthcoming!” says Schlag.

Other key achievements include developing the ARC: a framework for Access, Reciprocity and Conduct in psychedelic therapies, which was published in Frontiers in Psychiatry in 2023; and developing a lexicon for psychedelic research and treatment, described as “a key paper delineating a standardised terminology for clinical development and regulatory classification for psychedelic medicines.”

An upcoming project focused on psilocybin for palliative care will be announced over the summer.

“I would urge any organisation that shares our vision to join us in shaping the future of mental healthcare”, concludes Prof. Nutt.

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Psychedelic Health is a journalist-led news site. Any views expressed by interviewees or commentators do not reflect our own. We do not provide medical advice or promote the personal use of psychedelic compounds. Please seek professional medical advice if you are concerned about any of the issues raised.

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