In treatment-resistant depression, a single dose of 25 mg of psilocybin produced stronger correlations between certain psychedelic experiences and depression improvement three weeks later than lower doses. The intensity of psychedelic effects was dose-related, but scores for different doses overlapped considerably. At the 25 mg dose, dimensions of oceanic boundlessness and visual restructuralization, along with emotional breakthrough, showed the strongest correlations with reduced depression scores. The study does not establish causation and requires replication. The overlap in experience intensity across doses suggests unblinding to dose is less likely. Correlations between psychedelic experience and outcome indicate specificity in psilocybin's mechanism of action.
A single 25 mg dose of the synthetic psilocybin formulation COMP360 showed a longer time before depressive events recurred over 52 weeks compared with 1 mg and 10 mg doses in people with treatment-resistant depression. In the full group of 233 participants, the median time to a depressive event was 92 days for the 25 mg group, 83 days for the 10 mg group, and 62 days for the 1 mg group. Most participants had a depressive event by 12 weeks. Adverse events were rare; one case of mild suicidal ideation in the 1 mg group was considered possibly related to the drug. Larger long-term studies are needed to confirm these results.
In people with treatment-resistant depression receiving 25 mg psilocybin with monitoring and support, the therapeutic alliance before dosing had only weak correlations with improvement in depression scores at three weeks. Stronger correlations were seen with the intensity of the psychedelic experience itself, particularly emotional breakthrough and visual restructuring. Path analysis suggested that therapeutic alliance helped facilitate the psychedelic experience, but it was the psychedelic experience—not the alliance—that had stronger direct effects on clinical outcomes. The alliance's direct effect on antidepressant response was limited or absent.