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Researchers find that the psychoactive compound in mushrooms may be
helpful for patients with severe depression who did not respond to
conventional therapy.
Prof. David Nutt, the director of the Neuropsychopharmacology Unit in
the Division of Brain Sciences at Imperial College London in the United
Kingdom, is the senior author of the study paper.
The research was led by first author Dr. Robin Carhart-Harris, who is
head of Psychedelic Research at ICL, and the findings were published in
the journal Scientific Reports.
Dr. Carhart-Harris and his colleagues examined the effect of psilocybin
— which is a psychedelic drug that activates the brain's receptors for
serotonin, or the "happiness" hormone — in 19 patients in whom
conventional anti-depression therapies did not work.
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As he explains, the study shows "for the first time clear changes in
brain activity in depressed people treated with psilocybin after failing
to respond to conventional treatments."
Psilocybin shows lasting benefits
The researchers used functional MRI to analyze the brain activity of
these people both before and after treatment with psilocybin.
All patients had been diagnosed with "treatment-resistant," or severe,
depression. As part of the research, they received one 10-milligram dose
of psilocybin, and another dose of 25 milligrams a week later.
Participants were also asked to fill in a clinical questionnaire,
wherein they reported their experience.
All 19 patients showed significantly decreased depressive symptoms 1
week after the treatment. After 5 weeks, 12 of the 19 patients showed
lasting benefits and were therefore deemed to be "responsive" to the
treatment.
The whole-brain analyses performed by the researchers showed a decreased
cerebral blood flow in the temporal cortex, including in the
almond-shaped amygdala, or the brain's so-called fear hub, which
processes our "fight-or-flight" response.
The decreased blood flow in the amygdala correlated with the decrease in
depressive symptoms, and the researchers also found increased
resting-state functional connectivity, or stability, in the brain's
"default mode network."
An increase in the integrity of this network has previously been found
to be associated with depression, so observing this after treatment was
deemed intriguing by the researchers.
Psychedelics may 'reset' the brain
The findings point to a "reset mechanism," the authors propose, in which
the brain's networks are picked apart and put back together again.
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"Several of our patients," Dr. Carhart-Harris explains, "described
feeling 'reset' after the treatment and often used computer analogies.
For example, one said he felt like his brain had been 'defragged' like a
computer hard drive, and another said he felt 'rebooted.'"
"Psilocybin may be giving these individuals the temporary 'kick-start'
they need to break out of their depressive states, and these imaging
results do tentatively support a 'reset' analogy," Dr. Carhart-Harris
continues.
"Similar brain effects to these have been seen with electroconvulsive
therapy," he adds.
"Through collecting [...] imaging data we have been able to provide a
window into the after effects of psilocybin treatment in the brains of
patients with chronic depression," explains Dr. Carhart-Harris.
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"Based on what we know from various brain imaging studies with
psychedelics, as well as taking heed of what people say about their
experiences, it may be that psychedelics do indeed 'reset' the brain
networks associated with depression, effectively enabling them to be
lifted from the depressed state."
Dr. Robin Carhart-Harris
However, the researchers also note the limitations of their study. The
sample size was small, there was no control group, and they only applied
multiple testing corrections selectively.
Therefore, future studies should "challenge and develop" the findings of
this research, the authors write.
Dr. Nutt concurs, saying, "Larger studies are needed to see if this
positive effect can be reproduced in more patients. But these initial
findings are exciting and provide another treatment avenue to explore."
The researchers also caution against patients attempting to take drugs
on their own. They stress that in order to use the psychoactive compound
for treatment purposes, a special therapeutic setting is required.
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