Psychedelics are a class of psychoactive drugs that are known for their ability to produce profound alterations in perception, mood, and cognitive processes, including mystical and spiritual experiences, as well as sensory distortions, such as those resembling hallucinations.

The word “psychedelic” is derived from the Greek words ‘psychḗ’ meaning 'soul or mind' and ‘dēleín’ meaning 'to manifest'. Therefore, it literally means "mind manifesting". British psychiatrist Humphry Osmond coined the term ‘psychedelic’ in 1956, suggesting it in a letter to a fellow author - Aldous Huxley.

“Psychedelic” is a broad umbrella term for a diverse range of natural and synthetic substances. Examples of common psychedelics include:

• Psilocybin (a psychoactive ingredient of “magic mushrooms”)

• LSD (lysergic acid diethylamide)

• DMT (dimethyltryptamine, one of the active ingredients of the Ayahuasca plant brew)

• 5-meO-DMT

• MDMA (3,4-methylenedioxymethamphetamine)

• Ketamine

• Ibogaine

Psychedelic compounds may be categorised according to their chemical structure (tryptamines or phenethylamines), or to their pharmacological mechanisms in the brain (serotonergic or classic psychedelics, and atypical psychedelics).

Some psychedelics have been used by Indigenous communities for hundreds or thousands of years. Others were first synthesised in the early 20th century. By the middle of the 20th century, clinicians used psychedelics as adjuncts to psychotherapy, reporting a variety of benefits in treating depression and PTSD. However, in the 1970s they were categorized as schedule I controlled substances, which are said to have “no currently accepted medical use and a high potential for abuse”. This blocked mainstream research on these compounds for decades. Today, numerous psychedelic compounds are studied in laboratories and clinical trials.

Psychedelics have been used by a few indigenous communities for medicinal and spiritual traditions for millennia. In the West, our understanding of the psycho-pharmacological effects substances using the ‘scientific method’ began at the turn of the 19th century, when scientists learned how to isolate psychedelic compounds from their natural sources - such as mescaline from the peyote cactus - and produce novel ones.

From 1900 to 1950, Swiss, German and American chemists synthesised a wide range of psychedelic substances, including LSD and MDMA, followed by a burgeoning period of scientific and cultural exploration until the 70s. During this time, it is estimated that around 40,000 clinical study participants were treated with psychedelics, namely for conditions such as alcoholism, mood disorders and anxiety and depression associated with terminal illnesses.

From 1970, the United Nations (UN) Single Convention on Narcotic Drugs and the Convention on Psychotropic Substances restricted the extent to which these drugs could be researched by classifying them as Schedule I substances with “no currently accepted medical use and a high potential for abuse”.

From 1990 to 2010, a “Psychedelic Renaissance” took place, in which pioneers such as Rick Strassman, Franz Vollenweider, David Nutt, and Roland Griffiths, began a resurgence of research into these substances after 20 years of scientific censorship.

Today, the interest in psychedelic research has blossomed, driven by advances in brain imaging technology and a growing recognition of the need for more effective mental health treatments. This new era of research is marked by rigorous scientific studies exploring psychedelics for a range of mental health and neurological conditions with significant unmet needs. However, challenges remain, including small sample sizes, limited diversity in study populations, and variability in research methodologies.

To find out more about the history of psychedelics, check out the comprehensive timeline produced by Psychedelic Times.

Psychedelics have shown promise as a therapeutic tool for a variety of mental health conditions as well as neurological disorders. Here are some examples:

Depression and anxiety
Several clinical trials have found that psilocybin can rapidly reduce symptoms of depression in people who do not respond to traditional antidepressant medications. The effects of psilocybin can last for several weeks or months after a single dose. Moreover, psilocybin, MDMA and LSD have both been studied as potential treatments for anxiety disorders, such as social anxiety and PTSD.

End-of-life anxiety
Psychedelics have been studied as a way to alleviate anxiety and improve the quality of life for people with terminal illnesses. Some studies have found that a single dose of psilocybin can significantly reduce anxiety and depression in patients with cancer.

Post-traumatic stress disorder
There is evidence to suggest that psychedelics, such as MDMA and psilocybin, may have therapeutic potential for treating PTSD (Post-Traumatic Stress Disorder). Studies have shown that these substances, when administered in a controlled setting under the guidance of a trained therapist, can help individuals with PTSD process and integrate traumatic experiences, reduce symptoms of anxiety and depression, and improve overall well-being.

Substance use disorders: smoking, alcohol and opioid addiction
There have been some promising results from studies on the use of psychedelics such as psilocybin and LSD to treat addiction to alcohol, nicotine and opioids. One study, for example, found that a single dose of psilocybin was associated with a significant reduction in alcohol use in a small sample of participants with alcohol use disorder. One theory is that psychedelics can help people break free from ingrained thought patterns and behaviors that contribute to addiction. In another research, when 15 smokers took psilocybin two or three times along with cognitive behavioural therapy, 60% dropped the habit 30 months later. Most people saw a substantial reduction in cravings and the emotional aspects of withdrawal — the irritability, fear, and depression — seemed to be better.

Headaches
Psychedelics have shown promise in treating cluster headaches, a type of headache that is often severe and recurring. One study published in the journal Neurology found that psilocybin reduced the frequency and severity of cluster headaches in a group of 53 patients. The effects were long-lasting, with some patients experiencing relief for several weeks or even months after a single dose of psilocybin.

Another study published in the Journal of Headache and Pain reported that LSD, another psychedelic, was effective in treating cluster headaches in a small group of patients. The study found that LSD reduced the frequency and duration of cluster headache attacks.

Anorexia
Anorexia nervosa is the deadliest psychiatric disorder. In a small study published in 2020, researchers found that psilocybin-assisted therapy was associated with significant improvements in eating disorder symptoms, depression, and anxiety among patients with anorexia nervosa. However, this study had a small sample size and lacked a control group, so more research is needed to confirm these findings. A couple of clinical trials with psychedelic compounds are currently underway in this area.

You can browse the full list of ongoing clinical trials alongside indications they address here: Mapping Drug Development in Psychedelics

Psychedelics can have powerful psychoactive effects, inducing altered states of consciousness with changed visual and auditory perception, distorted sense of time and one's own body, and distinct thought and emotional processes. The incidence and intensity of these effects varies based on factors such as the particular substance, the dose, as well as the one’s current state of mind (“set”), surroundings (“setting”), and individual personality or biological traits. Psychedelics have been referred to as “non-specific amplifiers”, which reflects their ability to enhance whatever mental content is already present, and also points towards the influence of external stimuli on the psychedelic experience.

Psychedelic experiences can be deeply psychologically meaningful and impactful. In a conducive environment, they may lead to profound insights and personal growth by allowing individuals to step outside their habitual mental state and observe themselves and their reality with fresh eyes. Thus, psychedelics have the potential to bring about significant changes in personality, beliefs, and worldview.  

While the exact therapeutic mechanisms of psychedelics are still being explored, evidence suggests that, with proper support, they can help reset cognitive and behavioural patterns linked to mental health conditions. By temporarily reducing rigid thought patterns and mental defences, psychedelics may allow for the revision of deeply held beliefs and encourage more adaptive behaviours. However, this process can also surface painful emotions and past trauma, leading to challenging experiences. This highlights the importance of undergoing psychedelic therapy in a controlled setting, with thorough preparation and the guidance of a skilled professional.

While the functioning of psychedelics in the brain is not yet fully understood, modern studies have made significant progress in uncovering their mechanisms of action. Psychedelics can be studied from multiple perspectives, including molecular, cellular, network, and cognitive and behavioural levels. It should be noted that their precise neurobiological effects vary between substances. Classical (serotonergic) psychedelics - such as psilocybin, LSD, or DMT - form one category, while other psychedelics – like MDMA, ketamine, ibogaine - have some distinct properties (scroll to the bottom of this page for more substance-specific information). Here is an overview of current knowledge and theories:

Activation of serotonin 2A (5-HT2A) receptors

The primary effects of classical psychedelics come from their ability to bind and activate serotonin receptors, particularly the serotonin 2A (5-HT2A) receptor, which is why they are also known as “serotonergic” psychedelics. Yet, each substance has a slightly different receptor-binding profile, which may account for phenomenological differences in their elicited psychedelic experience.

Activation of 5-HT2A receptors, namely in the cerebral cortex, triggers a cascade of molecular and cellular mechanisms linked to changes in overall brain activity, which can be studied with brain imaging techniques.

The entropic brain

When measured in a normal state, the brain operates with relatively predictable patterns of electrophysiological activity within defined networks, consisting of key hubs and their connections. Under the influence of psychedelics, brain activity becomes less localised but more globally interconnected. In other words, individual regions believed to play a dominant role in maintaining our everyday conscious state become less active, while the communication between regions that don’t usually interact is increased. This phenomenon has been described as the “entropic brain”, reflecting a more dynamic and less predictable state of brain activity.

Suppression of the default mode network (DMN)

Psychedelics notably disrupt activity in key hubs of the default mode network (DMN). The DMN is the brain network involved in episodic memory recall and self-referential thinking, thought to play a central role in governing our sense of identity. Notably, heightened activation of the DMN has been linked to maladaptive rumination and risk of depression. Under the influence of psychedelics, the DMN becomes less active, a change associated with altered self-perception, including the experience of “ego dissolution”. One theory behind the therapeutic potential of psychedelics is that, by quieting the DMN, they can loosen rigid patterns of self-related thought, potentially leading to lasting psychological shifts and relief from depression symptoms after just a single treatment.

Relaxed beliefs under psychedelics (REBUS) model

These ideas have been elaborated upon with the REBUS (RElaxed Beliefs Under pSychedelics) model, a theoretical framework linking the brain’s response to psychedelics with their subjective effects and therapeutic potential. According to this model, psychedelics weaken top-down influence from the cortex – decreasing inhibitory control over other brain regions, and disrupting stable, long-held beliefs (or priors) – while simultaneously increasing bottom-up input from lower-level brain regions and sensory systems. This not only contributes to sensory and perceptual changes under psychedelics, but also to the formation of new priors.

Thalamic gating model

Another model for the effects of psychedelics in the brain is the thalamic gating model. The thalamus is a brain structure that acts as a relay station for sensory input, regulating the flow of information to higher-level brain regions. Psychedelics are thought to disrupt this filtering process, allowing an increased influx of sensory information into the cortex. This sensory overload is believed to contribute to the vivid sensory perceptual changes often experienced under psychedelics, leading external stimuli to take precedence over top-down beliefs about reality.

Neuroplasticity

Shifting from brain activity and cognitive models back to neurobiology, one prominent theory regarding the therapeutic potential of psychedelics is their ability to induce neuroplasticity. Neuroplasticity is the brain’s ability to continuously develop and adapt in response to external and experiential stimuli. While it is most prominent during critical periods of brain development - such as from conception through childhood and into early adulthood - it continues throughout life. Neuroplasticity can be understood at various levels, including molecular, cellular, and synaptic.

One of the primary ways that psychedelics may impact neuroplasticity is by binding to serotonin receptors in the brain, specifically the 5-HT2A receptors. This binding triggers a cascade of molecular events leading to the increased expression of genes associated with cellular and synaptic plasticity. As a result, this can promote neurogenesis and the strengthening and formation of new synaptic connections. This could help counteract the loss of synapses and neurons associated with conditions like depression, as well as possibly in neurodegenerative disorders (though research in this area is still limited).

Such changes may also provide a neurobiological basis for the creation of new patterns of thought and behaviour following the acute psychedelic experience. The ability to enhance neuronal proliferation and rewiring has been compared to processes occurring in the developing infants, when billions of connections form before being refined through synaptic pruning. By temporarily restoring this early-like plasticity, psychedelics may offer a unique therapeutic pathway for reshaping deeply ingrained patterns of thought and behaviour.

In support of the neuroplasticity theory, a recent seminal study in mice showed that psychedelics can directly activate a brain receptor called TrkB. This receptor, typically activated by brain-derived neurotrophic factor (BDNF) - a key biomarker of neuroplasticity - plays a crucial role in triggering molecular signalling cascades linked to neurogenesis and synaptic plasticity. Importantly, this process did not rely on 5-HT2A receptor activation, and was observed with ketamine as well as with serotonergic psychedelics.

The neuroplasticity theory has prompted researchers and drug developers to explore the therapeutic potential of novel substances that promote neuroplasticity in the brain without inducing psychedelic effects, sometimes known as “non-psychedelic psychedelics” or “psychoplastogens”.

Reopening of the social reward learning critical period

During development, the brain undergoes what are known as “critical periods” - windows of heightened plasticity during which specific functions, for example vision, language or social learning, are especially sensitive to external stimuli and individual experience. These windows typically close as we mature, making it more difficult to re-wire established connections within these functions. However, recent research suggests that psychedelics may temporarily re-open critical periods, specifically related to social reward learning, even beyond the acute psychedelic effects. Behavioural studies in mice found that psychedelics increased sensitivity to the hormone oxytocin-mediated neuroplasticity, which is associated with social bonding. Notably, this research presents a unified mechanism underlying the therapeutic potential of psychedelics, as these effects were observed across all tested substances, both serotonergic psychedelics and atypical ones, including MDMA, ketamine, and ibogaine. The period of critical period reopening appeared to vary in length depending on the duration of the psychedelic experience.

Psychedelic therapies do not simply consist in taking a psychedelic drug – they differ significantly from recreational use and involve structured, carefully-designed treatment protocols to achieve efficacy and safety. These include medical screening, preparatory sessions, supervised dosing sessions in a controlled setting, and post-dosing integration sessions. Most approaches incorporate some level of psychological support or psychotherapy. In practice, psychedelic therapies can encompass a range of different approaches. These may be tailored to the specific substance, targeted condition, treatment goals, and the regulatory or research context—such as clinical trials, drug development programmes, or other access frameworks.

The terms “psychedelic-assisted therapy” or “psychedelic-assisted psychotherapy” refer to a model in which psychedelic substances are used to facilitate therapeutic insight and breakthroughs. In this approach, the drug is believed to work synergistically with talk therapy, with therapeutic benefits emerging from their combined use rather than from either component alone. Other models may emphasise the drug itself, pairing it with a simplified psychological support framework aimed at ensuring participant safety and preparation, while intentionally avoiding active psychotherapeutic guidance. Even with this distinction, the type and content of psychological support or psychotherapy delivered alongside psychedelics can vary widely. The optimal approach remains a topic of ongoing research and debate within the field, and will likely differ based on the drug, indication and individual characteristics.

The exact details of the different components of psychedelic therapy can vary depending on the specific substance used, the condition being treated and overall therapeutic approach. However, most models share several key phases:

Screening

Before beginning treatment, each patient undergoes medical screening to ensure there are no contraindications. The specific exclusion criteria depend on the substance, targeted indication and research or regulatory context. Common factors that may disqualify a patient include a history of psychotic disorders or significant cardiovascular risk.

Preparation

Preparation sessions aim to educate the patient about the treatment, the psychedelic substance, its effects, and potential risks. They offer an opportunity to ask questions, plan logistics for the dosing day and establish a sense of trust between the patient and the care team. In models with more therapeutic involvement, preparation (usually up to three sessions) may also involve setting an intention for the experience, discussing psychological goals, and building therapeutic alliance.

Dosing session

The psychedelic substance is administered in a controlled environment, such as a dedicated hospital room, specialised clinic, or therapist’s office, designed to feel homey and comfortable. The route of administration varies depending on the substance and may be oral, inhaled, or intravenous. Participants are typically invited to relax in a reclined or seated position, often with eyes covered and specially composed music playlist playing. At least one trained facilitator or therapist will always be present to monitor the session and ensure patient safety.

During the psychedelic experience, patients are encouraged to surrender to the experience, allowing thoughts and emotions to emerge naturally and be addressed with openness and curiosity. Many revisit memories or explore deep psychological material, including past traumas that may underlie conditions such as depression or PTSD. Practitioners may provide emotional support but do not guide or interfere with the experience unless necessary. Their role is to create a safe, non-directive space where patients can navigate their inner process with reassurance and care.

Integration

Post-dosing sessions provide an opportunity to check in with patients after their psychedelic experience, and typically focus on integration. Integration consists of supporting patients to process and make sense of the insights accessed during the psychedelic experience, incorporating them into their personal narratives and converting them into meaningful changes in daily life. This may involve talk therapy, journaling, mindfulness practices, or other reflective techniques. Many consider this phase to be the most crucial part of psychedelic therapy, as it determines how the experience translates into long-term psychological growth and healing.

A holistic treatment approach

Unlike conventional psychiatric medications, psychedelic therapy extends beyond a typical pharmacological model of treatment. The psychedelic substances are not used as standalone drugs but rather embedded in a non-pharmacological therapeutic framework, serving as catalysts for a psychological healing process. Patients are encouraged to actively engage in their own recovery, rather than relying solely on medication to manage symptoms. This approach recognises that mental health cannot be reduced to isolated neurobiological mechanisms, and is shaped by biological, psychological, and social factors.

Rapid and lasting benefits from just one or two doses

Psychedelic therapy has the potential of producing rapid therapeutic effects, unlike traditional antidepressants such as SSRIs (selective serotonin reuptake inhibitors), which typically take weeks to show benefits. Additionally, instead of requiring daily medication over long periods, psychedelics often provide significant and lasting improvements after just one or a few treatment sessions. Clinical research suggests that the positive effects can persist for months to even a year following treatment.

Distinct therapeutic mechanisms

Conventional psychiatric medications work by targeting neurobiological pathways associated with mental health conditions, focusing on symptom management rather than addressing root causes. However, mental health is highly complex, and isolated pharmacological interventions often fail to capture its full scope. For example, while SSRIs remain the standard treatment for depression and anxiety, they only provide relief for about 25% of patients, and many report feeling emotionally blunted rather than truly improved. Traditional medications may help individuals cope with their mental illness, but they often do not directly facilitate deeper emotional healing.

The mechanisms of psychedelic therapy are fundamentally distinct. Instead of simply alleviating symptoms, psychedelic therapies are experiential treatments facilitating a direct engagement with the root causes of mental health struggles. This can offer a unique pathway to healing, especially for those who have not responded to conventional treatments. Psychedelics induce an altered state of consciousness characterised by a more open and dynamic brain state, which enables individuals to revisit deep-seated emotional patterns and past traumas. With the right therapeutic support, this can lead to profound personal insight, emotional breakthroughs, and lasting transformation, facilitated by enhanced neural connectivity and neuroplasticity. (You may read more about psychedelics’ mechanisms of action in the corresponding question above).

A transformative experience

While traditional psychiatric medications can help stabilise emotions, many individuals on SSRIs report feeling emotionally dulled or detached. In contrast, those who undergo a psychedelic experience often describe it as one of the most meaningful and transformative experiences of their lives. A defining feature of psychedelic therapy is its ability to profoundly shift perception and self-understanding. Many patients report moments of deep revelation or epiphany, gaining newfound clarity about their emotions, relationships, and sense of self. This process often leads to a renewed sense of emotional balance, connection, and purpose, fostering lasting psychological growth. By facilitating an immersive and holistic exploration of the mind, psychedelic therapy provides a unique opportunity for deep, enduring change that extends beyond symptom management.

Some psychedelic substances have known pharmacological interactions with specific classes of antidepressants and other psychiatric medications, which may pose safety risks. For this reason, combining treatments should never be attempted without the guidance of a qualified health professional.

Yet, the broader implications of combining psychedelics with other treatments remain an open question and a critical area of research for the development and implementation of psychedelic therapies. Many studies have excluded participants taking concomitant psychiatric medications, or those with comorbid medical conditions such as cardiovascular disease or liver dysfunction, to minimise risks and ensure reliable efficacy assessments in early clinical trials. As a result, our understanding of potential drug-drug or drug-disease interactions remains limited. This gap can be addressed with preclinical studies, larger-scale clinical trials, and real-world phase 4 studies.

There is some anecdotal evidence suggesting that ongoing treatment with antidepressants, particularly SSRIs (selective serotonin reuptake inhibitors), may dampen the subjective effects of psychedelics, but its impact on safety and therapeutic outcomes remains unclear. A study in healthy participants found that pre-treatment with the SSRI escitalopram for one week did not reduce the positive effects of psilocybin or hinder levels of brain-derived neurotrophic factor (BDNF) - a key protein linked to neuroplasticity - but actually appeared to mitigate negative drug effects, such as anxiety, cardiovascular effects, and other adverse events observed in the group that had not been given escitalopram.

Research shows that psychedelics are generally physiologically and psychologically safe when delivered in controlled and supportive settings. However, side effects are a fact of life that needs to be accepted, managed in the context of benefits and carefully monitored. Psychedelic treatments, despite being considered generally safe, present real risks, as virtually any effective treatment does. The various compounds used in clinical trials, and in the future – in psychedelic-assisted therapies, have different safety profiles. For example, while psychedelic compounds like psilocybin and LSD are non-toxic and non-habit forming, MDMA can influence blood pressure and ketamine can become addictive over time if not used under strict supervision. As with any other medical treatment, it is crucial to consider the possible benefits and risks and make an informed decision based on that.

To find out more about the safety profiles of specific compounds, see the question What are the main psychedelic compounds and their potential therapeutic applications, effects and risks?

Psychedelics are powerful substances that can produce a range of physical, psychological, and emotional effects. Overall, the risks associated with psychedelics depend on a variety of factors, including the specific substance used, the dose consumed, the individual's physical and psychological health, and the setting in which the drug is consumed. Patients should be informed that these compounds could leave the user vulnerable to emotional, physical or sexual harm, as well as psychiatric complications. These risks are way much higher if the psychedelics are used in a non-medical context, e.g. recreational settings or unsafe environments.

Psychological distress
Psychedelics can cause intense and unpredictable changes in perception, thought, and mood, which can lead to feelings of confusion, anxiety, and paranoia. In some cases, these experiences can trigger underlying mental health conditions or exacerbate existing ones. In very rare cases psychedelics can cause a psychotic reaction. It is more likely among users with a family history of schizophrenia or psychosis; or, if taken with medications that increase serotonin levels, which could cause a dangerous overload. To mitigate these risks, patients should be appropriately screened for pre-existing mental health conditions and properly supervised throughout the duration of their altered state of consciousness as well as in a time following the session.

Physical health risks
Some psychedelics can increase heart rate, blood pressure, and body temperature, which can be dangerous for people with underlying cardiovascular problems. In addition, some psychedelics can cause nausea, vomiting, and other physical symptoms.

Risks associated with unsupervised use
When used outside of a clinical or therapeutic setting, psychedelics can be dangerous, especially if consumed in unknown or unsafe environments and in combination with other substances. Users may be at risk of accidents, injuries, or exposure to harmful substances.

Risk of addiction
While classical psychedelics are not considered to be physically addictive, some people may develop psychological dependence on them and may feel compelled to use them repeatedly.

Sexual abuse risk
Psychedelics induce a specific kind of vulnerability, as they are known to enhance suggestibility and sexual feelings. Many of these substances can leave patients vulnerable to abuse and manipulation by their therapists or guides. While instances of sexual abuse during psychedelic-assisted therapy are relatively rare, they can have devastating consequences for patients and can erode trust in the therapeutic process. Indeed, among all the reports of sexual abuse and ethical misconduct within psychedelic therapies, the concerns being raised are not about the psychedelic substance itself, but about the therapy that is accompanying it. Many survivors of these abuses agree that psychedelics have the potential to be a powerful healing agent but need to be handled with great care and responsibility. Addressing the risk of sexual abuse in psychedelic research and therapy should be adequately prioritized by proper screening and training of therapists and staff, clear guidelines for therapist-patient interactions, monitoring and oversight of the therapists and staff.

Psychedelic substances such as psilocybin, DMT, LSD, and MDMA are classified as Schedule I drugs under the 1971 United Nations Convention on Psychotropic Substances. This designation means they are considered to have no accepted medical use and a high potential for abuse and dependence - despite emerging evidence suggesting their therapeutic potential. This classification has significantly hindered scientific research and the development of psychedelic therapies for several reasons:

Barriers to access

Regulations governing research with Schedule I substances vary by country, but the classification can create significant obstacles for researchers seeking access to these drugs for scientific studies. Since Schedule I drugs are presumed to have no medical benefit, obtaining the necessary licenses, permits, and regulatory approvals for studies can be a lengthy and complex process, blocking many scientists from pursuing this research.

Limited research funding

The Schedule I status also restricts government and institutional funding for studying psychedelic substances, leading to a shortage of well-funded, large-scale studies. As a result, much of the current research relies on small sample sizes and limited resources.

As an example, before LSD was banned, the U.S. National Institutes of Health (NIH) funded over 130 studies exploring its clinical applications. However, since its prohibition, the NIH has funded none. Thus, for many years, no companies were producing medical-grade psychedelics, making it nearly impossible to procure these substances for clinical trials.

Lack of research diversity

Access restrictions and funding limitations risks concentrating psychedelic research within a small group of institutions and researchers and a lack of diversity in perspectives, methodologies, and study populations. This narrow research landscape can introduce biases and limit broader scientific exploration of psychedelic therapies.

Slowed progress in treatment development

Ultimately, these barriers impede the development of safe and effective psychedelic treatments that could help people suffering from mental health conditions such as depression, PTSD, and addiction. By delaying research, these restrictions may prolong the suffering of individuals who could potentially benefit from psychedelic therapies.

Some of the main challenges include:

Legal and regulatory issues
Psychedelic substances such as psilocybin and MDMA are currently classified as Schedule I drugs, meaning they are considered to have no medical use and a high potential for abuse. This makes it difficult for researchers and clinicians to conduct studies and offer these therapies to patients.

Safety concerns
While psychedelics have been shown to be relatively safe when administered in a controlled setting, they can cause adverse reactions in certain individuals, particularly those with a history of mental illness or cardiovascular problems. Ensuring that patients are properly screened and monitored during treatment is essential.

Standardization of dosing and administration
There is currently no standardized protocol for dosing or administering psychedelic substances, which can make it difficult to compare studies and ensure consistent outcomes.

Integration and aftercare
Psychedelic experiences can be profound and transformative, but they can also be difficult to integrate into everyday life. Ensuring that patients receive adequate support and follow-up care after treatment is essential to maximize the benefits of these therapies.

Access and affordability
Psychedelic-assisted therapies may not be accessible or affordable to all patients, which can limit their potential impact. Addressing issues of accessibility and affordability, including reimbursement by health insurance, is crucial to ensuring that these therapies can reach those who stand to benefit the most.

Stigma and public perception
Psychedelic substances have a long history of being demonized and stigmatized, and there is still significant public resistance to their use in a therapeutic context. The public will need to see psychedelic medicine as real medicine. Clinicians will have to rethink and expand their definition of what an antidepressant is and even how we should be treating depression. Overcoming this stigma and educating the public about the potential benefits of these therapies will be an ongoing challenge.

If you are interested in enrolling on a psychedelic clinical trial, here are two pages where you can find lists of the ongoing clinical trials:

Psychedelic Support

Atlas of Psychedelic Research

Becoming a psychedelic-assisted therapy practitioner typically requires a combination of education, training, and experience. Here are some general steps you can take to become a psychedelic-assisted therapy practitioner:

Obtain a relevant degree
Many psychedelic-assisted therapy practitioners have a background in psychology, counseling, social work, or a related field. Obtaining a degree in one of these fields can provide a strong foundation for working in psychedelic-assisted therapy.

Gain experience in mental health
Experience working in mental health or counselling is often a prerequisite for becoming a psychedelic-assisted therapy practitioner. This may involve working as a counsellor, social worker, or therapist in a clinical setting.

Obtain necessary licenses and certifications
Depending on the local requirements, a practitioner may need to obtain specific licenses or certifications to practice psychedelic-assisted therapy. This may include a license to practice psychotherapy or counseling, or a certification in psychedelic-assisted therapy from a recognized organization.

Keep up with current research and best practices
The field of psychedelic-assisted therapy is constantly evolving, so it is important for practitioners to stay up-to-date on the latest research and best practices in the field. This may involve attending conferences or workshops, reading academic journals, or networking with other practitioners in the field.

Complete specialized training
Specialized training in psychedelic-assisted therapy is also necessary to become a practitioner. This may involve completing a certification program or training course in psychedelic-assisted therapy. See below a list of such training offered by several organizations:

• MAPS

• The California Institute of Integral Studies (CIIS)

• COMPASS Pathways

• Psychedelics Today

• Fluence

• Institute of Psychedelic Therapy

• MIND Foundation

Psilocybin, a compound produced by many species of fungi, is one of the most well-studied psychedelics. To acknowledge its safety record and potential for treating depression more effectively than existing therapies, the Food and Drug Administration in the US designated psilocybin a breakthrough therapy in 2018 and 2019 for treating drug-resistant depression and major depressive disorder.

Therapeutic applications
Psilocybin, typically taken in pill form, has the potential to treat substance use disorders, including alcoholism and nicotine addiction, as well as depression.

What it does
A psilocybin trip can last more than six hours, and some people describe a positive “afterglow” lasting for months. Effects of psilocybin may include:

• Altered perception of reality, such as changes in visual and auditory perception

• Increased emotional and sensory awareness

• Changes in mood, including feelings of euphoria and anxiety

• Altered sense of time and space

• Spiritual experiences and feelings of interconnectedness

• Potential for "bad trips" or experiences of anxiety, paranoia, and confusion.

Risks
Overall, psilocybin has a low risk of toxicity and very low potential for addiction or dependence. In clinical trials, side effects are usually temporary and mild, and though psilocybin experiences are sometimes challenging because they can bring up difficult emotions, participants often report they are among the most meaningful experiences of their lives, producing benefits that frequently last for months.

Some of the potential risks of psilocybin use include:

• Psychological effects: Psilocybin can cause a range of psychological effects, including changes in perception, mood, and thought processes. Some people may experience anxiety, paranoia, or confusion. It can also cause distressing hallucinations or feelings of panic in some patients, especially at high doses.

• Flashbacks: Some people may experience flashbacks or persistent changes in perception and thought processes after using psilocybin.

• Increased risk of accidents: Psilocybin use can impair cognitive and motor functioning, which can increase the risk of accidents and injury.

• Interactions with other substances: Psilocybin can interact with other substances, including prescription medications and over-the-counter drugs, which can increase the risks of adverse effects.

• Medical emergencies: While psilocybin is not known to be toxic or lethal on its own, using too much or combining it with other substances can lead to medical emergencies.

• Risk of emotional instability: People who have a history of mental illness or emotional instability may be at a greater risk of adverse psychological effects from psilocybin use.

For more information on the therapeutic potential of Psilocybin, please visit the Drug Science website.

First synthesized in 1956, ketamine is used today as an anaesthetic by veterinarians and in emergency or combat medicine. The World Health Organization has included it on its Essential Medicines List since 1985. Every ambulance carries it; requiring no oxygen supply and posing no risk of respiratory suppression, it is one of the safest drugs one can receive in a crisis. Because it is the one psychedelic that’s never been illegal, researchers have been able to explore ketamine’s potential as a mental health treatment — and build a case for its use in humans.

Ketamine works differently from other psychedelics. Most psychedelics — like LSD, MDMA and those derived from plants — operate by affecting serotonin receptors, which alter mood and happiness. Ketamine affects a different class of brain receptors that are important for learning and memory. Both kinds of receptors are found in the brain’s prefrontal cortex, which might explain why ketamine and the other psychedelics seem to have similar impacts on mental health.

Therapeutic applications
Many brain disorders — like schizophrenia, depression and anxiety — are characterized by atrophy in the prefrontal cortex. There is strong evidence, though not yet conclusive, that ketamine helps people with psychiatric disorders by promoting regrowth over time in neurons in this area. That could help explain the near-immediate feelings of relief that users report, which is one of the reasons it has been used in the treatment of suicidal patients.

Esketamine, a form of ketamine, showed such promise for treating major depression, often faster than other drugs, that the F.D.A. approved its limited use in early 2019.

What it does
The effects of ketamine can vary depending on the dose, route of administration, and individual factors such as body weight, tolerance, and sensitivity. Some common effects of ketamine include:

• Analgesia: Ketamine can provide pain relief by blocking certain receptors in the brain and spinal cord. Users taking a low dose might feel as though they’re floating or that their body is numb.

• Sedation: Ketamine can cause sedation or anesthesia, which can be useful during surgical procedures or other medical interventions.

• Dissociation: Ketamine can produce a sense of detachment from reality or a feeling of being outside one's body, which is sometimes described as a "K-hole."

• Euphoria: Ketamine can produce feelings of euphoria or a sense of well-being.

• Cognitive impairment: Ketamine can impair cognitive function, including memory, attention, and executive function.

• Hallucinations: Ketamine can cause visual and auditory hallucinations, which can be either pleasant or unpleasant.

• Increased heart rate and blood pressure.

Risks
Like any substance, ketamine use can come with risks and potential side effects. These risks are increased when ketamine is used recreationally or in higher doses than prescribed.

Some of the potential risks of ketamine use include:

• Addiction: Ketamine has the potential to be addictive, especially when used recreationally or in higher doses than prescribed.

• Psychological effects: Ketamine use can cause a range of psychological effects, including hallucinations, delusions, paranoia, and dissociation.

• Physical effects: Ketamine use can also cause a range of physical effects, including increased heart rate, blood pressure, and body temperature, as well as nausea, vomiting, and dizziness.

• Cognitive impairment: Ketamine use can impair cognitive functioning, including memory, attention, and decision-making.

• Respiratory depression: Ketamine can also cause respiratory depression, which can be dangerous or even fatal in high doses.

• Potential for overdose: Using too much ketamine can lead to an overdose, which can cause seizures, coma, or even death.

• Interactions with other substances: Ketamine can interact with other substances, including alcohol, which can increase the risks of adverse effects and overdose.

For more information on the therapeutic potential of Ketamine, please visit the Drug Science website.

LSD (lysergic acid diethylamide), first synthesized in 1938, is a very potent hallucinogen. It is synthetically made from lysergic acid, which is found in ergot, a fungus that grows on rye and other grains. LSD, also known as acid, is a powerful psychedelic substance that can have both potential therapeutic applications and risks.

Therapeutic Applications
Research suggests that LSD may have therapeutic benefits for a range of mental health conditions, including depression, anxiety, and addiction (it’s shown promise for treating alcohol addiction). Some studies have found that LSD assisted therapy can lead to significant reductions in symptoms of depression and anxiety, as well as improvements in mood, well-being, and spiritual experiences. LSD may also have potential applications in end-of-life care, with research suggesting that it may help alleviate anxiety and depression in patients with terminal illnesses.

What it does
LSD is known to affect serotonin receptors in the brain, leading to altered perception, mood, and thought processes. The effects of LSD can be intense and unpredictable, varying widely from person to person. LSD users have reported feelings of bliss during their trip, being able to see sound and having mystical experiences as well as a sense of closeness with others.

Some of the potential effects of LSD may include:

• Altered perception of reality, such as changes in visual and auditory perception

• Heightened sense of creativity and imagination

• Altered sense of time and space

• Emotional and spiritual experiences

Potential for "bad trips" or experiences of anxiety, paranoia, and confusion

Risks
LSD can be potentially risky, particularly if used in high doses or in uncontrolled settings. Some of the potential risks of LSD use may include:

• Anxiety, paranoia, and confusion

• Hallucinations and delusions

• Potential for accidents and injury

• Potential for "flashbacks" or re-experiencing aspects of the trip

• Potential for exacerbation of underlying mental health conditions

• Risk of serotonin syndrome when combined with other substances or medications

For more information on the therapeutic potential of LSD, please visit the Drug Science website.

MDMA (3,4-methylenedioxymethamphetamine) is a synthetic drug that alters mood and perception. It is also known as ecstasy, molly, or XTC, and is classified as a psychoactive drug that produces feelings of increased energy, pleasure, emotional warmth, and distorted sensory and time perception.

MDMA is typically taken orally in pill or tablet form, but can also be crushed and snorted or injected. It is commonly used in social settings such as clubs or parties, but can also be used therapeutically in certain medical contexts.

Therapeutic applications
MDMA has been studied primarily as a treatment for post-traumatic stress disorder (PTSD) leading to significant reductions in PTSD symptoms, such as flashbacks, nightmares, and avoidance behaviors, as well as improvements in mood, interpersonal functioning, and quality of life. MDMA may also have potential applications for treating anxiety, depression, and addiction.

By facilitating a feeling of connection, MDMA can create a strong “therapeutic alliance” between participants and therapists, building a level of trust to help a person feel protected while engaging with intense emotions, memories, and thoughts.

What it does
The effects of MDMA can be intense and last for several hours, with the experience varying widely from person to person and depending on the dose, setting, and mindset of the individual. MDMA is chemically similar to both stimulants and hallucinogens, and it stimulates the release of neurotransmitters such as serotonin, dopamine, and norepinephrine in the brain, which can cause a sense of euphoria and heightened sensory perception.

In the words of one participant, ‘it’s like being in a box full of puppies.’ You can actually feel safe to bring up things that were otherwise very uncomfortable.

Some of the potential effects of MDMA may include:

• Heightened empathy and feelings of connection to others

• Increased sociability and talkativeness

• Positive mood and an increased sense of well-being

• Altered perception of time and space

• Potential for physical sensations, such as heightened touch sensitivity

Risks
MDMA can be potentially risky, particularly if used in high doses or in uncontrolled settings. Some of the potential risks of MDMA use may include:

• Anxiety, paranoia, and confusion

• Overheating and dehydration

• Risk of serotonin syndrome when combined with other substances or medications

• Potential for accidents and injury

• Potential for long-term neurotoxicity with repeated use, meaning damage to nerve cells in the brain

• In extreme cases - lasting kidney and organ damage as well as heart arrhythmias, especially in patients with related pre-existing conditions

• In rare cases - building tolerance to MDMA

For more information on the therapeutic potential of MDMA, please visit the Drug Science website.