A single dose of psilocybin eased depression within days, but its edge over placebo faded within a year

A recent Swedish study found that a single 25-mg dose of psilocybin, a psychedelic compound, provided rapid relief from depression in patients with moderate to severe recurrent major depressive disorder. The effects were noticeable as early as the second day after dosing and persisted for over three months. By the end of a year, however, the difference between the psilocybin group and a placebo group became negligible.

The study, published in JAMA Network Open, comprised 35 adults with recurrent depression, randomly divided into two groups. One group received the psilocybin, while the other received a niacin-based placebo, both under double-blind conditions where neither the participants nor the researchers knew who received which. The participants also underwent psychotherapeutic support sessions.

On a clinician-rated scale, the psilocybin group showed a significant improvement compared to the niacin group within days, but this advantage faded by one year. On a self-report scale, the psilocybin group experienced greater symptom reduction from day 2, with the difference lasting more than three months. By day 42, remission rates were notably higher in the psilocybin group (53%) as opposed to the niacin group (6%).

After a year, the remission rates in both groups remained close, with 53% in the psilocybin group and 41% in the placebo group. The psilocybin group's remission rate held steady from the start, while in the placebo group, it rose from 12% to 41%. The study also noted that both groups started antidepressant medication at similar rates during the follow-up year. Despite generally mild side effects, two participants in the psilocybin group experienced severe anxiety that required medical attention.