A new pilot study suggests that a single dose of psilocybin may significantly reduce depression symptoms in military veterans with severe treatment-resistant depression (TRD), with effects lasting up to a year in some patients.
Dried psilocybin mushrooms. (Photo credit: Kevin J. Beaty/Denverite).
Researchers from Ohio State University and Stanford University School of Medicine tracked 15 veterans who received a 25 mg dose of psilocybin. All participants had been diagnosed with TRD, defined as a major depressive episode that had not responded to at least five previous treatments or had persisted for more than two years.
Ten of the participants completed a 12-month follow-up. At six months, 80% met the criteria for treatment response—defined as a 50% or greater reduction in depression scores—and 50% achieved remission. By month nine, improvements had begun to decline. At the one-year mark, 40% still met response criteria and 30% remained in remission.
While overall depression levels remained significantly lower than at baseline throughout the year, the benefits appeared to diminish over time. Researchers noted that the increases in depression scores after six months did not reach statistical significance, but they emphasized the need for further studies to better understand the long-term potential of psilocybin in this population.
The study, published in the Journal of Affective Disorders, is the first to examine long-term psilocybin use in veterans with severe TRD. The authors caution that the open-label design and small sample size are limitations, but say the results support further controlled research.
