There has been little research on the mechanism of action of “magic mushrooms” on the brain. A growing number of studies suggested that perhaps the mushrooms' key compound could work magic for certain mental disorders. New research in Proceedings of the National Academy of Sciences sheds light on why one of the mushrooms' hallucinogenic chemical compounds, psilocybin, may hold promise for the treatment of depression.
The researchers explored the effect of psilocybin on the brain, documenting the neural basis behind the altered state of consciousness that people have reported after using magic mushrooms. “We have found that these drugs turn off the parts of the brain that integrate sensations - seeing, hearing, feeling - with thinking,” said David Nutt, co-author of the study and researcher at Imperial College London in the United Kingdom.
Psilocybin is illegal in the United States and considered a Schedule 1 drug, along with heroin and LSD. Schedule 1 drugs “have a high potential for abuse and serve no legitimate medical purpose in the United States,” according to the Department of Justice.
Nutt's study is a preliminary and small, with only 30 participants. His group used magnetic resonance imaging (MRI) to look at how the brain responds to psilocybin, from normal waking consciousness to a psychedelic state.
The blood flow to various parts of the brain was recorded. These measurements revealed decreases in the amount of blood flowing through parts of the volunteers’ brains. Surprised by the result, the researchers repeated the experiment with another group, using a different scanning technique. The same pattern of reduced activity emerged, most pronounced in the hubs that connect different parts of the brain — including the thalamus and parts of the cingulate cortex.
The study found that the more psilocybin shuts off the brain, the greater the feeling of being in an altered state of consciousness, he said. It's not the same as dreaming, because you're fully conscious and aware, he explained. The medial prefrontal cortex, the front part of the brain in the middle, appears to be crucial - it determines one thinks, feels and behaves. Damage to it produces profound changes in personality, and so if this is switched off, the sense of self becomes fragmented, Nutt said. That's what happens when psilocybin decreases activity in it. “Some people say they become one with the universe,” he said. “It's that sort of transcendental experience.”
Psilocybin also affects the anterior cingulate cortex, which is over-active in depression, Nutt said. Some patients with severe depression that cannot be treated with pharmaceuticals receive deep brain stimulation, a technique of surgically implanting a device that delivers electrical impulses directed at decreasing activity in that brain region. Psilocybin could be a cheaper option, Nutt said. “Chemically switching off might have very profound beneficial effects,” says Nutt, who suspects that psilocybin could also be useful for treating obsessive-compulsive disorder. “It may help people completely locked into a mindset that drives their lives.”
It's counterintuitive that a hallucinogenic drug would de-activate rather than stimulate key brain regions, although other studies have shown a mix of results regarding psilocybin turning brain areas on and off, said Roland Griffiths, a professor of psychiatry and neuroscience at the Johns Hopkins University School of Medicine. Griffiths was not involved in Nutt's study, but has also researched the effects of psilocybin.
“Decreasing the activity in certain hubs in the network may allow for a more unconstrained conscious experience,” says Matthew Johnson, an experimental psychologist at Johns Hopkins University School of Medicine in Baltimore who studies psilocybin and other hallucinogens. “These drugs may lift the filters that are at play in terms of limiting our perception of reality.”
Although scientists have found many positive effects of psilocybin in experimental trials, there are of course potential dangers. Some people have frightening experiences while on psilocybin. The fear and anxiety responses of magic mushrooms can be so great that, when taken casually in a non-medical setting, people can cause harm to themselves or others. They may jump out a window or run into traffic because of a panic reaction. There's just not enough known yet about the long-term safety of psilocybin to say whether it could also do damage to the brain, Griffiths said. “There'd have to be changes in the brain for these long-lasting memories and attributions to occur,” Griffiths said. “We don't know how those changes occur, and why.”
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