Researchers in Sweden report that a single dose of psilocybin, a psychedelic compound found in mushrooms, can provide rapid relief from depressive symptoms. Results from a small-scale Phase II trial, published today in JAMA Network Open, show that patients experienced an improvement as soon as two days after treatment, with effects persisting for longer than three months.
”Our results suggest that psilocybin can provide rapid, clinically meaningful improvement in depression and may serve as an alternative to standard treatment when fast symptom reduction is important,” says Hampus Yngwe, MD, consultant psychiatrist and PhD student at the department of clinical neuroscience of the Karolinska Institutet in Stockholm.
Major depressive disorder is commonly treated with selective serotonin reuptake inhibitors (SSRIs), but most patients do not respond to this treatment or become resistant. In addition, their effects can typically take several weeks to be noticeable, and side effects are common.
Previous research had shown that a single dose of psilocybin can have antidepressant effects in people with treatment-resistant depression or anxiety disorders in patients with advanced cancer. The current study looked instead at the effects of this compound on “common” forms of major depressive disorder.
The study recruited a total of 35 people with moderate to severe recurrent depression, between 20 and 65 years of age. They were randomly assigned to receive either a single 25mg dose of psilocybin or niacin, an active placebo that causes a noticeable physical reaction. All patients received psychotherapeutic support before, during, and after treatment.
Participants were evaluated using the Montgomery–Åsberg depression rating scale (MADRS) to assess treatment effects at multiple time points after dosing. After a week, the group who received psilocybin saw an average MADRS score reduction of 9.7 points, compared to 2.4 points in the placebo group, and these effects persisted after two weeks and six weeks. At this point, 53% of participants who received psilocybin were in remission, compared to 6% in the placebo group.
A self-reported version of the MADRS revealed that patients saw antidepressant effects as early as day two after dosing, and continued to experience these positive effects for over three months.
A year after treatment, all patients who received psilocybin treatment remained in remission. However, many of the patients who received the placebo had also recovered at that point, showing no major statistical difference between both groups.
“The long-term effects are uncertain,” says Yngwe. “Repeated treatments may be needed to prevent relapse. This needs to be investigated in larger studies.”
Because the effects of psilocybin are strong and easily recognizable, many participants were able to tell whether they had received the treatment or the placebo. This is a common challenge scientists face when studying psychedelic treatments that can make it difficult for patients and researchers alike to separate the effects of the treatment from their expectations. “We want to understand how factors such as treatment expectations and lack of blinding affect the results, as previous studies may have exaggerated the treatment effects,” notes Yngwe.
Next, the researchers will analyze data from PET scans, blood, and cerebrospinal fluid samples collected from all patients before and after dosing. This will help them understand the physiological changes induced by psilocybin, and how these influence its observed antidepressant effects.
”Research suggests that the interaction between parts of the brain is impaired in depression and that this may be linked to changes in the connections between nerve cells, known as synapses,” says Yngwe. “In preclinical studies, psychedelics have been shown to stimulate synaptic growth. We therefore want to investigate whether psilocybin alters synaptic density in the brain.”
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