Short answer: In a small open-label pilot study of U.S. veterans with treatment-resistant depression, psilocybin-assisted therapy was associated with reduced anxiety and with improvements in quality of life and functioning, and PTSD symptoms also declined. These findings are preliminary.
Fifteen participants were followed for up to 12 months after a single supported session. Anxiety dropped early and stayed lower over time. Quality of life and daily functioning improved, but these were no longer statistically significant after accounting for concurrent improvements in depression. PTSD scores decreased at all time points, though the study was not powered to test this rigorously.
Caveats include no control group, no blinding, a small sample, and industry involvement. The intensity or mystical quality of the acute experience did not predict outcomes. Full details are summarized in the Journal of Affective Disorders report indexed on PubMed.
Bottom line: encouraging signals, but stronger randomized trials are needed.