Psilocybin for Depression, Explained by a Doctor

Physician Mike Hansen makes the clinical case for psilocybin, the compound in magic mushrooms, as a possible treatment for major depressive disorder. He opens with a case from his own ICU practice: a patient whose depression had not responded to therapy or antidepressants, and who did not survive. He then walks through published trials, from Johns Hopkins to an emerging phase 3 program, on what the research shows and does not. The video is a doctor's research review, not a treatment recommendation, and it repeatedly flags open questions.

Why standard antidepressants leave a gap

Hansen calls depression the most common psychiatric disorder worldwide, with over 30 FDA-approved drugs that, he says, tend to work only modestly better than placebo. He cites a 2021 estimate that just under a third of the roughly 9 million Americans on antidepressant treatment are treatment-resistant, with side effects from nausea and dizziness to weight gain and sexual side effects.

What early psilocybin trials found, and how it may work

A 2020 Johns Hopkins study paired a single dose with supportive psychotherapy and relieved depressive symptoms for up to a month, with a follow-up finding improvement held for some participants up to a year. Ingested psilocybin converts to psilocin, which acts on serotonin receptors, mainly 5-HT2A, through a different route than SSRIs; Hansen says it appears to reduce a bias toward negative thoughts via the cortex and amygdala, and affects the default mode network, a self-referential circuit often overactive in depression. A 2021 mouse study found a single dose produced a lasting rise in dendritic spines, a marker of neuroplasticity, still visible a month later. An fMRI study of about 60 participants found psilocybin reduced connectivity in depression-linked networks and increased it elsewhere, in ways that tracked with symptom improvement; those on escitalopram (Lexapro), an SSRI, showed no comparable change. More in Psychedelics and Brain Changes.

The 2022 phase 2 trial, and its limits

A 2022 New England Journal of Medicine study tested 25mg, 10mg, and a 1mg control dose in people with treatment-resistant depression, with therapist support during six-to-eight-hour sessions. Only the 25mg group showed significantly lower symptoms at three weeks, with peak effect the day after dosing, though the benefit had largely faded by three months. Hansen flags real limits: about 80 percent had side effects, severely depressed patients were unevenly distributed across dose groups, and a small number reported suicidal thoughts or self-harm during follow-up, a period when they had also been weaned off their usual medication. The numbers, he says, are too small to draw firm conclusions from alone.

Risk, and where the research is headed

Citing a survey of mushroom users, Hansen notes 4 in 10 rated their experience among the most challenging of their lives, though most still said they valued it; see Psychedelic Safety and Harm Reduction. He closes with a 2023 trial of 52 people where a single moderate dose reduced symptoms versus placebo for at least two weeks with no serious adverse events, the first hallucinogen trial to reach phase 3, the stage before FDA submission. It is run by COMPASS Pathways, a UK company, with results expected around 2025. Psilocybin is also being studied for PTSD, OCD, anorexia nervosa, and alcoholism.

Key takeaways

• ●A 2020 Johns Hopkins trial pairing psilocybin with supportive psychotherapy relieved depressive symptoms for up to a month, with some participants improved at one year.
• ●Psilocybin converts to psilocin, which acts on serotonin 5-HT2A receptors through a different pathway than SSRIs.
• ●Brain imaging suggests psilocybin reduces overactive connectivity in the default mode network, unlike escitalopram in the same comparison.
• ●A 2021 mouse study found a single dose produced a lasting rise in dendritic spines, a marker of neuronal connectivity.
• ●In a 2022 phase 2 trial, only a 25mg dose (not 10mg) significantly reduced symptoms versus a 1mg control, and the benefit faded by three months.
• ●About 80 percent of phase 2 participants had side effects, and safety data on suicidality are hard to interpret given the trial's small size.
• ●A 2023 trial run by COMPASS Pathways became the first hallucinogen study to reach FDA phase 3, with results expected around 2025.
• ●Hansen frames the evidence as promising but early, and says it is too soon to know how often repeat dosing would be needed.