Psychedelic use is rising sharply in the US, UK, Australia and other countries. 

• Psychedelic drugs have been legalized or decriminalized in multiple US cities and two states in the last three years. 
• There has also been a surge of positive media coverage of psychedelic drugs and their healing potential, as well as billions of dollars in funding to psychedelic companies and retreats. 
• However there has been no public health education campaign on the risks of psychedelics, leading the population to rely on over-hyped media reports on their miraculous healing benefits. 
• In 2018, the prevalence of young American adults’ past-year use of non-LSD hallucinogens was 3.4%. In 2021, that use increased to 6.6% (Monitoring the Future study)
• In the UK, use of magic mushrooms grew 62% between 2020 and 2023, and by 37.5% in 2024 alone. 
• In Australia, use of magic mushrooms has doubled since 2019.
• The percentage of people who used psychedelics in the last year in Colorado and Oregon increased 65% after decriminalization.

Research and media attention for the last 20 years has largely focused on the benefits of psychedelic drugs for mental health and spirituality. These benefits are exciting and undeniable. However, there are also potential risks, according to emerging data. 

There has been little research on adverse psychedelic experiences or difficulties after psychedelic usage, and even less empirical research on what helps people who have them. This is partly because most research in the last 15 years has been funded and carried out by ‘true believers’ in psychedelics’ potential to heal humanity. 

Breeksema et al (2022) conducted a systematic review of adverse experiences reported in clinical psychedelic trials, and found that many psychedelic trials did not systematically assess AEs.  A recent study of adverse events in trials of esketamine (a form of ketamine) found that 40% of adverse events went unreported, and when participants felt suicidal, this was often not attributed to the drug by the trial scientists.

Some research that directly focuses on adverse psychedelic experiences has begun to emerge in the last few years. For example:

People sometimes have difficult / challenging / bad psychedelic experiences that they don’t feel they benefited from.

52% of people who responded to the Canadian Psychedelic Survey said they’d had an intensely challenging trip, and 45% thought no good had come of it. The most common difficulties were:  mental or sensory overload (61%), social paranoia (51%), worried about mental or physical health (42%), worried about never being the same after trip (34%), worried about dying (26%) (Lake et al, 2023).

In another survey of 1221 people who regularly took psychedelics, more than half reported experiencing an adverse experience at least once – the most common were ‘being frightened’ and ‘sadness’ , though people also felt afraid the trip would last forever and that they might lose their mind. (Kruger et al, 2024) 

In a recent Rocky Mountain Poison and Drug Safety (RMPDS) survey of over 2000 psychedelic users, 25% reported an adverse event – of which, 61% of respondents reported physical adverse events, the most common cardiovascular; 25% reported going to an emergency room or urgent care after taking a psychedelic; 39% reported ‘visual distortions that persisted after the other effects of the drug wore off’. 

Sometimes people can be a danger to themselves and others during bad trips. In June 2023, one veteran shot two people at a music festival after he took magic mushrooms and thought the world was ending. 

The growing unregulated underground psychedelic market can be dangerous. One product sold as containing mushrooms, ‘Diamond Shruumz’, led to 46 hospitalizations and two deaths in 2024. 

Sometimes post-psychedelic difficulties extend beyond the acute effects of the drugs and last days, weeks, months, years or the rest of a person’s life. 

• In our survey of 608 people who report extended difficulties after a psychedelic experience (Evans et al 2023), one third reported difficulties lasting longer than a year and one sixth longer than three years. The most common reported difficulties were anxiety, social disconnection, derealization, existential struggle and continued visual distortions. And 8% of survey respondents had taken psychedelics in a therapeutic or clinical setting, so harms happen even under ‘safe’ settings.
• Our research was used in the defence trial of pilot Joseph Emerson, who tried to crash a plane two days after taking magic mushrooms, when he thought he was in a dream.
• In another study, 8.9% of people reported functional impairment lasting longer than a day after a difficult trip. 2.6 % reported seeking medical, psychiatric, or psychological assistance in the days or weeks following their most challenging psychedelic experience. 6% considered harming themselves or others (Simonsson et al, 2023). Again, the most common adverse mental health effect reported was anxiety.
• In another paper, 39% of people who had a challenging experience said it was one of the five most difficult experiences of their life. Of those whose experience occurred >1 year before, 7.6% sought treatment for enduring psychological symptoms. 16% of those surveyed felt they had not ultimately benefitted from the experience (Carbonaro et al, 2016).
• 7% of people report persisting negative effects 2-3 months after naturalistic use of magic mushrooms, in this 2023 study by Nayak et al.  
• In a large survey, 14% of people reported feeling more anxious for an extended period due to their psychedelic usage, and half of these people felt these personality changes were permanent and unwanted (Weiss at al, 2023).
• 12% of people who’ve taken ayahuasca said they felt functional impairment lasting longer than a day, for which they sought psychological assistance (Bouso et al, 2022). The most common adverse mental health effects in the Global Ayahuasca Survey were feeling socially disconnected, anxiety, low mood and ‘feeling energetically attacked’. 
• 4-4.5% of people who had taken psychedelics reported persistent visual distortions which they found disturbing (Hallucination Persistent Perception Disorder) (Baggott et al 2011). To be clear, the online questionnaire found that 4.2% of respondents who had used psychedelics in the past reported persistent visual disturbances that were severe enough that the patients would consider treatment, although this is possibly an overestimate given that people with visual issues were more likely to complete the survey

Adverse events and extended difficulties still happen under clinical conditions.  

• 7% of patients in Compass’ trial of psilocybin for treatment-resistant depression experienced treatment-emergency serious adverse events. (Compass SEC filing). You can watch a testimony by one participant who felt more suicidal in the days after her treatment here (she ultimately felt she had improved compared to before the treatment but that it was ‘touch and go’ for a few weeks. If she hadn’t experienced intense therapeutic support she thinks she could have taken her own life. 
• 7% of participants in MAPS’ phase 3 trial of MDMA for PTSD reported increased feelings of suicidality. (McNamee et al, 2023)
• Two out of 30 participants in Braxia’s trial of psilocybin for treatment-resistant depression reported severe extended difficulties lasting to the present day (two years after the trial), which they felt were not reported in the results. One of the participants says her condition is now so bad she has applied for the assisted-dying program in Canada. 

The risks of psychedelics include psychotic episodes, accidental deaths and suicides. 

• Emergency department admissions connected to psychedelics went up 69% between 2016 and 2021 in California (Tate et al 2023).
• In Simonson et al’s 2023 study, 6.7% of people who reported challenging experiences said they considered harming themselves or others. CPEP research includes several reports of people feeling suicidal and also reports by family members whose loved ones took their own life. 

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Other forms of psychedelic harm  

Psychedelics can lead to suggestibility in those taking the drugs and ego inflation in those taking them, making people vulnerable to sexual and financial abuse and cultic manipulation 

• Sexual abuse by psychedelic facilitators: there have been several high-profile cases of this, as documented in the Power Trip podcast. There are also many more undocumented cases of sexual abuse and rape during psychedelic sessions in the underground (McNamee et al, 2023)
• In Kruger et al’s 2024 survey of 1221 psychonauts,  8% reported that they or someone they knew was the victim of inappropriate sexual contact by a psychedelic sitter, guide, or practitioner. 
• In the Rocky Mountain Poison and Drug survey of over 2000 people who had taken psychedelics, 13% said they had someone force sexual advances on them while they were under the influence. 
• Financial abuse involving psychedelics: there are several cases of unscrupulous people seeking money from people while they are on or in the days after taking psychedelics. There are also examples of people using psychedelics to control vulnerable people and take control of their finances. See the case of George Sarlo and Vicky Dulai (who is still on the board of MAPS). 
• Psychedelics and cults: there are several historical accounts of cult-leaders who used psychedelics as a tool of indoctrination and control, including the Manson family, The Family in Australia, the Osho cult in Oregon, and the Aum Shinrikyo movement in Japan.

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Adverse events on ketamine

The ketamine market is already up and running in the US and elsewhere, as ketamine was FDA approved as an anesthetic and is now used as an off-label treatment for depression and multiple other conditions, without much oversight. Indeed, during the pandemic, the DEA allowed ketamine to be ordered online and delivered to your door. There are now over 700 ketamine clinics around the US, up from around 50 clinics in 2019. There is more research on the physical and mental risks of ketamine, but not much.

• There is some evidence to suggest ketamine can become psychologically addictive, and many anecdotal accounts of this. The problem has been particularly studied in China,  where ketamine addiction has been a societal problem. 
• There is also evidence of ketamine leading to physical harm, such as bladder injury and liver injury. 
• There is also some emerging evidence of psychological harm when people have powerful ketamine experiences and don’t feel able to let go – see Breeksema et al’s 2022 study. 
• Matthew Perry, star of Friends, died in a ketamine-related accident after he was illegally prescribed ketamine, having been prescribed it legally for addiction and depression. 

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What could be done to reduce these risks?

We encourage a three-pronged effort: 

• LEARN more about psychedelic harms and harm reduction through empirical research
• COMMUNICATE more accurately what harms are possible and how one may be able to mitigate or manage them through public health campaigns
• SUPPORT those who feel they have been harmed by psychedelics through information, specialist clinics and peer support groups

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Made by The Challenging Psychedelic Experiences Project. We are a non-profit academic research center dedicated to learning about psychedelic harms and what helps people avoid them or mitigate them.