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Psilocybin Therapy Still Benefits People With Depression One Year After Treatment, Study Finds

By Leo Bear-McGuinness

Published: Feb 17, 2022   
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The anti-depressive effects of psilocybin can last for at least a year, according to new research.

Published in the Journal of Psychopharmacology, the study followed 24 participants with a history of depression. All participants received two doses of psilocybin and supportive therapy sessions.

Almost all participants reported feeling significantly less depressed when they met up with the researchers a week after treatment, and most continued to report lower depression scores 3 months, 6 months, and 12 months after their second psilocybin trip.

The researchers behind the study say their findings demonstrate psilocybin’s remarkable anti-depressive effects, which appear much longer-lasting than those of ketamine.

A trip to remember

Psilocybin is the active psychedelic component of magic mushrooms, and has shown promise when used in therapy settings for the treatment of depression.

To test how long these anti-depressive effects can last for, the research team from Johns Hopkins University recruited 27 participants, all aged between 21 and 75 and all with a history of depression.

Just 24 participants (three dropped out) received two doses of psilocybin – a 20 milligrams per 70 kilograms (mg/kg) dose and a 30 mg/70kg dose, respectively – during two therapy sessions that were held two weeks apart.

Participants were asked to return for a check-up one day and one week following each session, along with further check-ups 1 month, 3 months, 6 months, and 12 months after the second session.

When averaged, all 24 participants had a significantly lower depression score one week after their sessions, which remained significantly lower by the 12-month mark.

“Psilocybin not only produces significant and immediate effects, it also has a long duration, which suggests that it may be a uniquely useful new treatment for depression,” Roland Griffiths, a professor of neuropsychopharmacology at the Johns Hopkins University School of Medicine, said in a statement.

“Compared to standard antidepressants, which must be taken for long stretches of time, psilocybin has the potential to enduringly relieve the symptoms of depression with one or two treatments.”

Griffiths and his colleagues admit that their study had a few limitations, however. For instance, eight patients (33 percent) started a course of antidepressants at some point during the trial, so the researchers can’t be fully certain that the low depression scores of those participants weren’t also kept low by their concurrent medication. Yet, at the 12-month mark, the depression scores of these participants didn’t significantly differ from those who didn’t start taking antidepressants.

Other limitations, according to the researchers themselves, include “the small sample size, the predominately Caucasian, non-Hispanic study sample, and exclusion of those judged to be at elevated risk of suicide.”

Nonetheless, the Johns Hopkins team say their study still demonstrates the great potential of psilocybin as an anti-depressant, even when compared to other psychedelic drugs with known anti-depressant effects, like ketamine.

“The present study highlights a key potential advantage of psilocybin treatment over ketamine in that antidepressant effects after just two administrations of psilocybin paired with psychological support appear to be sustained through 12 months, which is well beyond the duration of effects reported with ketamine,” the researchers write in their paper.

“Future research is needed to explore the possibility that efficacy of psilocybin treatment in MDD [major depressive disorder] may be substantially longer than the 12 months observed in the present study, as has been suggested in a study that documented decreases in depressive symptoms up to 4.5 years following psilocybin treatment in patients with cancer-related distress.”

Psilocybin therapy

Previous research into psilocybin has suggested that the compound exerts its psychedelic effects by acting on the body’s serotonin 2A receptor (5-HT2AR). Through this mechanism, and the presence of a trained therapist, many psychedelic researchers believe that psilocybin could become a valuable drug for the treatment of depression.

Indeed, a recent trial conducted by a team at Imperial College London found that psilocybin matched the antidepressant potential of the more conventional antidepressant drug escitalopram.

Remarking on the study last April, Robin Carhart-Harris, head of the Centre for Psychedelic Research at Imperial, said that the “results comparing 2 doses of psilocybin therapy with 43 daily doses of one of the best performing SSRI [selective serotonin reuptake inhibitor] antidepressants help contextualize psilocybin’s promise as a potential mental health treatment. Remission rates were twice as high in the psilocybin group than the escitalopram group.”


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