Single-dose psilocybin therapy shows promise for veterans with treatment-resistant depression

A recent study published in the Journal of Affective Disorders suggests that a single dose of psilocybin may offer hope for U.S. military veterans facing severe, treatment-resistant depression. Many veterans who had endured years of depression despite numerous treatments showed significant improvements following psilocybin-assisted therapy. Yet, the results were mixed, with some participants experiencing limited relief. This study marks the first to explore psilocybin’s potential specifically for veterans with treatment-resistant depression.

Treatment-resistant depression refers to a form of major depressive disorder that does not respond to conventional treatments, such as antidepressant medications or psychotherapy. Individuals with treatment-resistant depression often experience prolonged and severe symptoms despite multiple attempts to alleviate their condition. For those affected, it can feel as though no options are left, leading to further feelings of hopelessness and distress. The risk of suicide and other health complications can be high, making it an important area of focus in mental health research.

Psilocybin-assisted therapy is an emerging approach that combines the use of psilocybin, a psychedelic compound found in certain “magic” mushrooms, with therapeutic support. Psilocybin is known for its mind-altering effects and has been studied for its potential to provide rapid and sustained relief from depressive symptoms.

In a therapeutic setting, psilocybin is administered in a controlled environment under the guidance of trained professionals. Participants are often prepared in advance and receive support during and after the experience, helping them process and integrate their insights. Some research suggests that psilocybin may affect brain regions associated with mood and perception, allowing individuals to experience shifts in their perspective on life and emotional struggles, even with just a single dose.

The motivation behind the new study stemmed from the unique challenges faced by U.S. military veterans, who experience high rates of treatment-resistant depression and related conditions like post-traumatic stress disorder. Many veterans struggle with depression as a result of trauma, combat exposure, and other stressors that complicate their mental health. Conventional treatments often fall short in this population, leading researchers to investigate alternative options.

The research team conducted their pilot study at the Veterans Affairs Palo Alto Health Care System and Stanford University. They recruited 15 veterans, ages 18 to 65, who had experienced depression resistant to at least five treatment attempts, or who had been struggling with depression for over two years. Participants underwent a rigorous screening process that included detailed medical and psychiatric assessments. To ensure safety, individuals with a history of psychosis, active substance use disorders, or untreated medical issues were excluded from the study.

After the initial screening, each participant attended three preparatory therapy sessions to build a rapport with the therapists, learn about psilocybin’s effects, and establish goals for their experience. The psilocybin sessions took place in a calm, comfortable setting with low lighting, cushions, and music to help participants feel at ease. During these sessions, veterans received a single 25 mg dose of synthetic psilocybin under the supervision of trained therapists who remained present throughout the session to provide support and ensure safety.

Afterward, participants had a 90-minute integration session to discuss and make sense of their experience. Follow-up assessments were conducted over a 12-week period, with clinical evaluations at specific intervals (Weeks 1, 2, 3, 6, 9, and 12) to monitor changes in depression symptoms, suicidal thoughts, and overall well-being.

The primary measure of improvement was the Montgomery-Åsberg Depression Rating Scale (MADRS), a commonly used scale for assessing the severity of depression. Three weeks after the psilocybin session, participants’ average MADRS scores had dropped significantly, indicating a substantial reduction in depressive symptoms. At this three-week point, 60% of participants met the criteria for “response” (a 50% or greater reduction in MADRS scores), and 53% met the criteria for remission, meaning their depression symptoms had reduced to very low levels.

By the study’s end at 12 weeks, 47% still showed a response, and 40% remained in remission. In other words, about half of the participants no longer met the threshold for a significant response or remission at the study’s conclusion. This outcome highlights the variability in how individuals respond to psilocybin, indicating that while some veterans found meaningful relief, others saw little improvement in their symptoms.

“Due to media attention, there are heightened expectations of miraculous response levels in psychedelic research trials,” the researchers wrote. “Even in this pilot study, about a third of participants did not have an antidepressant response to a single dose of psilocybin at the primary endpoint, and by the study endpoint 50% no longer met response criteria. Future studies must be cautious to mitigate the expectations of participants so that those who do not respond to this treatment are able to navigate feelings of disappointment.”

“Too often, patients are approaching these new tools as a ‘last-ditch effort’ in their attempt to recover from depression, and risks of increased suicidality or other self-harm behaviors could be heightened. It is critical to measure and manage participant expectations prior to dosing, and to prepare participants for an unknown outcome—one that may not meet their expectations.”

Interestingly, the researchers found no significant link between the intensity of participants’ psychedelic experiences and their improvements in depression symptoms, suggesting that psilocybin’s therapeutic effects may not rely solely on the depth of the psychedelic experience itself.

Psilocybin was generally well-tolerated. Some participants reported mild side effects like headaches, nausea, and mild back pain during the dosing day, but these symptoms resolved within a day. No severe adverse events or increases in suicidal ideation were observed during the study. For participants who had tapered off antidepressants before the study, four chose to restart them by the end of the follow-up period.

It is important to note that as an open-label pilot study, this research lacked a control group and involved a small sample size, which limits the ability to generalize the findings. Additionally, both participants and researchers were aware that everyone in the study would receive psilocybin, which may have influenced the outcomes.

The study design also required participants to taper off existing medications, which might have impacted their response to the psilocybin treatment. Larger trials with placebo groups, longer follow-up, and varied dosing methods could help confirm these findings and improve understanding of psilocybin’s effectiveness in the veteran population.

Looking forward, researchers will need to examine whether psilocybin’s effects endure over the long term and whether these benefits extend to other individuals with complex mental health needs. Additional studies are planned to explore how brain function may change after psilocybin treatment and to examine responses to psilocybin in a broader veteran population.

The study, “Single-dose psilocybin for U.S. military Veterans with severe treatment-resistant depression – A first-in-kind open-label pilot study,” was authored by Sara Ellis, Catherine Bostian, Wendy Feng, Eileen Fischer, Garrett Schwartz, Katherine Eisen, Melanie Lean, Elizabeth Conlan, Michael Ostacher, Scott Aaronson, and Trisha Suppes.