A small phase 1 study in adults with metastatic cancer who had only a partial response after an earlier group psilocybin retreat found that a second group session was feasible and appeared safe. The protocol included three preparation meetings, one dosing day starting at 35 mg, and four integration meetings, with an optional 10 mg booster at 60 to 90 minutes; participants were not required to stop antidepressants.
Among 13 people who completed the intervention, no serious adverse events were reported. Transient increases in blood pressure, nausea, and headache were the most common effects; seven received the booster without new serious safety signals.
Exploratory measures suggested reductions in anxiety and depression scores by day 8 with some persistence up to 24 weeks, and a higher rate of self-reported complete mystical experiences compared with the first session. However, the sample was small, there was no control group, and multiple protocol changes were introduced, so effectiveness and generalizability cannot be determined.
Details are summarized on PubMed. Larger controlled trials are needed before drawing firm conclusions.