Recent research indicates that psychedelic substances may not offer a significant advantage over conventional antidepressants in treating depression. While drugs like psilocybin, LSD, and DMT have recently garnered considerable attention for their potential in addressing various mental health conditions, a persistent challenge in this research domain is the difficulty in concealing the administration of real drugs versus placebos. Participants can often discern whether they have received a psychedelic due to its discernible hallucinogenic effects.
When this factor is carefully considered, studies suggest that psychedelics can indeed be effective for depression. However, their efficacy appears to be on par with, rather than surpassing, that of established antidepressants.
Balázs Szigeti, from the University of California, San Francisco (UCSF), commented on the findings. “Our results do not disprove the exciting results about psychedelic treatments,” he stated. “We also show that psychedelics are effective at treating depression; it is just that they are not more effective than open-label [unblinded] traditional antidepressants, which feels underwhelming given the attention [on psychedelics].”
The Challenge of Blinding in Psychedelic Trials
Hallucinogenic substances have demonstrated promise in treating conditions such as depression, anxiety, and obsessive-compulsive disorder. The established benchmark for drug development typically involves comparing a new treatment against a placebo. This method aims to isolate the treatment’s effects from the placebo effect, where a patient’s symptoms improve due to belief and expectation rather than the therapeutic agent itself.
However, in the context of psychedelic research, participants often recognize whether they have been given the active psychedelic compound. This inherent characteristic makes true blinding—where neither participants nor researchers know who receives the placebo—extremely difficult to achieve.
Methodology and Findings of the Study
To address this methodological hurdle, Szigeti and his colleagues undertook a comprehensive review of 24 clinical trials. Eight of these trials focused on psychedelic-assisted therapy (PAT), which combines psychotherapy with psychedelic administration. The remaining 16 trials involved open-label studies of traditional antidepressants. In these open-label trials, both the researchers and the participants were aware of the treatment being administered. This approach bypasses the crucial element of blinding, which is considered a hallmark of rigorous scientific testing in most clinical studies.
The research team observed that traditional antidepressants appeared to perform only slightly better than PAT, with a difference of approximately 0.3 points on a 52-point depression-rating scale. This marginal difference was deemed neither statistically nor clinically significant, suggesting comparable outcomes between the two approaches.
Previous studies have generally shown psychedelics to outperform placebos by around 7.3 points. In contrast, antidepressants have typically shown an advantage of about 2.4 points when compared against placebos. The current researchers propose that a substantial portion of the observed advantage for psychedelics might be attributed to participants’ ability to identify whether they received a psychedelic. “Ours and other studies provide emerging evidence that unblinding suppresses the placebo response,” Szigeti noted.
Expert Reactions and Future Directions
Matthew Johnson, associated with Sheppard Pratt hospital in Towson, Maryland, and involved in some of the reviewed studies, described the review as “intriguing” with a “clever approach to addressing the placebo question in psychedelic trials for depression.” He also raised concerns about some researchers’ motivations, suggesting that a “religious-like zeal to show psychedelics are effective” might sometimes overshadow a more “principled approach of trying to really test hypotheses.”
Rayyan Zafar at Imperial College London emphasized the need for direct head-to-head comparisons between psychedelics and antidepressants, rather than solely against placebos, to fully understand their respective effects. “The jury is still out scientifically,” he stated.
To date, only one trial has directly compared a psychedelic against an antidepressant. This study tested psilocybin against escitalopram, a selective serotonin reuptake inhibitor (SSRI) antidepressant, and found no significant difference in their ability to alleviate depression.
Methodological Critiques and Alternative Approaches
Robin Carhart-Harris, also from UCSF and a participant in the escitalopram trial, voiced a common criticism regarding the methodology of the latest study. He pointed out that comparing trials with diverse designs, including variations in sample size and participant selection criteria, may not always yield conclusive results. Carhart-Harris likened the approach to “comparing apples with oranges” rather than a direct “apples with apples” comparison.
In an effort to mitigate the problem of unblinding, researchers are exploring various strategies. For instance, a study in September investigating LSD for anxiety reduced the likelihood of participants guessing their treatment by administering lower doses of the drug to the control group. This approach aimed to induce mild hallucinogenic effects without significantly impacting mental health. Another strategy involved administering a sedative that can cause amnesia to participants in a psilocybin trial, with the intention of erasing their memory of the psychedelic experience.
Journal reference: JAMA Psychiatry DOI: 10.1001/jamapsychiatry.2025.4809