Psychedelic substances like psilocybin, LSD, and DMT are being explored as potential treatments for depression, but research suggests they may not be as effective as traditional antidepressants. Despite the promising results, the challenge remains: many participants in these studies can identify if they received a psychedelic or a placebo due to the distinct hallucinogenic effects.

According to Balaz Szigeti from the University of California, San Francisco (UCSF), “Our findings highlight that while psychedelics show effectiveness in treating depression, this isn’t necessarily comparable to the effects of traditional antidepressants.” He noted a growing interest in psychedelic treatments, yet cautioned against conflating their efficacy with unblinded trials.

Research indicates that hallucinogens show potential in alleviating depression, anxiety, and obsessive-compulsive disorder. In typical drug development, treatments are primarily tested against placebos, mitigating the placebo effect—wherein individuals experience symptom relief through expectation. However, due to the identifiable nature of psychedelic experiences, ensuring true double-blind conditions in these studies proves problematic.

To navigate this issue, Szigeti and his team analyzed 24 clinical trials. Their research encompassed eight focusing on psychedelic-assisted therapy (PAT), integrating psychotherapy with psychedelics, and 16 open-label trials evaluating conventional antidepressants. Open-label designs lack the blinding typical in rigorously controlled studies.

The results revealed that conventional antidepressants minimally outperformed PAT by just 0.3 points on a 52-point depression scale, a difference deemed neither statistically nor clinically significant.

Historically, psychedelics outperformed placebos by 7.3 points, whereas traditional antidepressants showed a 2.4-point advantage over placebos. However, researchers argue this discrepancy may largely stem from participants being able to recognize their treatment assignment. “Our findings and others suggest that unblinding may suppress the placebo response,” Szigeti concludes.

Matthew Johnson, a professor at Johns Hopkins University, remarked, “This review presents a pragmatic approach to evaluating placebos in psychedelic depression trials.” He added that some researchers may pursue results with a bias to prove psychedelics’ effectiveness, veering away from a principled testing approach.

Meanwhile, Rayan Zafar, a professor at Imperial College London, emphasized the necessity of directly comparing psychedelics with antidepressants, stating, “The science remains inconclusive.” Following one study, psilocybin was tested against escitalopram, a selective serotonin reuptake inhibitor, but did not yield significant differences in depression alleviation.

Robin Carhart-Harris, also from UCSF and involved in the escitalopram trial, criticized the methodological diversity across studies. Comparing trials with dissimilar designs, including varying sample sizes and inclusion criteria, often leads to inconclusive results. “To draw accurate comparisons, we must analyze similar studies rather than disparate ones,” he insists.

In September, a study explored using LSD for anxiety disorders, aiming to reduce unblinding by administering a lower dose that could still induce hallucinogenic effects without affecting mental clarity. In another psilocybin trial, sedatives were employed to induce amnesia, erasing participants’ memories of their experiences.