In recent years, the conversation around psychedelic medicine has shifted from hushed discussions to headline news, with many media articles trumpeting positive scientific findings. Studies have found psychedelics effective for a wide range of mental health conditions, including depression, post-traumatic stress disorder, and substance abuse, and even physical conditions such as chronic pain.
Results have been so promising that three states, Oregon, Colorado, and New Mexico, have created pathways for psychedelics to be legally administered there. And at least in part because of the positive research news, illegal use of the drugs—a category that includes psilocybin (the active ingredient in magic mushrooms), lysergic acid diethylamide (LSD), ayahuasca, and other compounds that alter consciousness—has risen across the United States. For example, psilocybin use in people over 30 increased by nearly 200 percent between 2019 and 2023, with many saying they took the drug to improve a mental health condition or chronic pain.
Momentum is building towards a possible psychedelic drug approval by the U.S. Food and Drug Administration (FDA) in the next few years. Yet some in the field say the research continues to have significant problems that make broad conclusions about their benefit premature.
Despite all the hype, “we cannot conclude anything as of yet about the safety or efficacy of psychedelic therapy” for many of the conditions it’s been touted to treat, says Michiel van Elk, a cognitive neuroscientist at Leiden University in the Netherlands, who coauthored an analysis in 2023 of the research’s shortcomings.
Some of the red flags took the spotlight last year, when the FDA rejected one of the most well-studied of the drugs, methylenedioxy-methamphetamine (MDMA), as a treatment for post-traumatic stress disorder. Even MDMA requires another large clinical trial to address lingering concerns, van Elk says.
Some issues plaguing psychedelic research stem from the youthfulness of the field. Although scientists preliminarily studied the drugs during the 1950s and 60s, most of the research has happened in the past decade. But other hurdles are specific to experimenting with mind-altering substances. Here are three of the major concerns.
1. Psychedelic studies have been shockingly small.
Studying these compounds is admittedly challenging. The drugs must be administered in person, generally in the presence of two trained facilitators who stay with each clinical trial participant for the six to ten hours the substance remains active. People also generally talk to therapists several times in the weeks before and after the experience. Plus, the medicine is time-consuming to get, due to restrictive government regulations. All told, running a single participant through a psychedelic study can cost tens of thousands of dollars, van Elk estimates.
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To make studies affordable, most psychedelic research has included a small number of participants. One widely touted study finding benefits of psilocybin for major depression involved just 27 participants. Only 39 people took part a study documenting LSD’s advantages for treating anxiety.
Even the two studies submitted to the FDA in 2024 seeking approval for MDMA included 90 and 104 participants, respectively. By contrast, when the diabetes drug Ozempic was approved in 2017, its manufacturer submitted results in more than 4,000 people.
In studies this small, a few individuals having unique experiences can skew the findings, especially if the people differ from the average to start. “People who agree to these trials may not reflect the general population: They may be more desperate, more resistant of conventional treatments, more willing to try something wildly different from the norm,” says Frederick Barrett, a neuroscientist and director of the Center for Psychedelic and Consciousness Research at Johns Hopkins University School of Medicine.
Only larger studies can confirm positive results from these small trials. “If you want to say anything meaningful, you need to increase sample sizes by hundreds of participants,” van Elk says.
One way to bring up the numbers is to pool results. Researchers did this in 2024, combining nine clinical trials on psilocybin for depression, which together found the drug twice as effective as a placebo, the inert substance used for comparison in drug trials. But even this pooled analysis, while lending support to prior results, involved just 436 total participants.
2. People are bummed when they figure out that they didn’t get the drug.
The most reliable studies are “double-blind,” where neither the person giving the medicine nor the person taking it knows whether they got the drug or the placebo. This helps keep people from incorrectly attributing health improvements to the medicine.
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But it’s nearly impossible to keep study participants from the fact that they’ve taken a psychedelic when the room starts singing or their hands disappear before them. “Psychedelic studies go through the motion, but it’s functionally not blinded. Everybody figures it out,” says Balázs Szigeti, a clinical data scientist in the Translational Psychedelic Research program at the University of California, San Francisco, who studies this issue.
People who don’t get the drug seem to especially disappointed—more so than with other medications. “Nobody wants to be in the placebo group,” Szigeti says. “It’s a great conversation when at cocktail parties you tell your friends you’re going to be in a psychedelic drug trial. But imagine months later at the same social gathering when you have to tell them nothing happened.”
This letdown may skew results, causing placebo-takers in psychedelic studies to underreport improvements. In a 2024 review, researchers found that people getting placebos in clinical trials testing the antidepressant escitalopram reported greater improvements in their depression levels than comparable studies for psychedelics. The wider gap between the psychedelic and placebo group artificially makes psychedelics look better, especially when they are compared to antidepressants, Szigeti says.
In reality, the two treatments may be more evenly matched. Szigeti compared results from psychedelic and antidepressant studies without a placebo group, where everyone got an active treatment, and his unpublished data suggest they actually have similar effects.
Of course, that may not be a bad thing. Antidepressant pills must be taken daily and come with side effects like weight gain and sexual disfunction. In comparison, one or two psychedelic sessions, which seem to convey lasting effects, could provide an appealing alternative for some patients. But such a finding would be far from the hype “that psychedelics can cure depression,” Barrett notes.
Scientists have been unable to find a placebo that does not tip off participants. They’ve tried a form of vitamin B that causes tingling and flushing, a cough medicine that can make people woozy, and even low doses of the psychedelic itself. But when people are asked during the clinical trial, most know they were not given the psychedelic.
A more effective approach may be to randomize people earlier in the process so the placebo group never knows they could have gotten a psychedelic, Szigeti says. Studies could also be designed with a so-called cross-over design where everyone eventually gets the psychedelic, minimizing the disappointment of those who initially do not.
3. It’s unclear how addictive some substances are.
One of the biggest concerns raised by the FDA advisory committee assessing MDMA was the potential for abuse should the drug become legally available.
Committee members complained that the company submitting the application, Lykos Therapeutics, had not asked study participants if they experienced euphoria or elation while on the drug—a sign some might seek to later abuse it. More than two million people in the U.S. illegally use MDMA, known on the street as Ecstasy or Molly—making it the fourth most common street drug after marijuana, cocaine, and methamphetamine.
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Psilocybin and LSD are less likely to be psychologically addictive than MDMA, Barrett says. In lab studies, animals exposed to an addictive drug like cocaine seek it out to the exclusion of food and water, but “you have to bend over backwards” to get animals to take these psychedelics, he says.
Still, the potential for abuse is rarely addressed in psychedelic research, even though critics think it always should be. “Absence of data is not evidence of absence,” van Elk says.
The potential for addiction is one reason drug companies are working to produce psychedelics that convey a health benefit without inducing the hallucinations or euphoria that might entice people to seek out these substances.
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As the field of psychedelic science matures and seeks broader acceptance, including perhaps FDA approval of one or more of the drugs, a growing number of researchers are starting to take critiques of their work to heart.
“People are becoming aware that we potentially face a credibility crisis,” van Elk says, “and that we need to do everything we can to make sure that we do the science according to the highest standards possible.”
