All mushrooms have a bit of magic about them. Neither animal nor plant, these are life-forms that appear as if from nowhere after rain and that we like to think pixies and toads use as umbrellas and stools.
But the name “magic mushroom” is reserved for those containing psilocybin, a compound that has spectacular effects on the minds of humans who ingest enough of it: euphoria, awe, sensory enhancement, spiritual experiences, revelatory thoughts, and hallucinations.
For many people, the experience is positive, but not for all. A “bad trip” can be fraught with anxiety, panic and paranoia. Very rarely, intoxication leads to serious accidents and self-harm, and persistent psychotic symptoms.
The earliest archaeological evidence for the use of psychoactive mushrooms dates back to 3000 years ago, in Mexico. But they only started piquing the interest of western science and culture in the 1950s.
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After ingestion, psilocybin is converted to psilocin, a molecule structurally similar to serotonin, which transmits signals between nerve cells. Psilocin binds to several of the same receptors, disrupting normal patterns of communication in the brain, and increasing connectedness between circuits that are usually quite distinct.
This resonates with accounts of psilocybin intoxication in which the senses blend into one another, unrelated thoughts and ideas flow together, inanimate objects become loaded with emotional meaning and the distinction between the self and one’s surroundings dissolve.
This blurring of boundaries between the internal and external worlds might help explain psilocybin’s effectiveness in treating severe depression in some people by temporarily interrupting the rigid, introspective thought processes associated with rumination.
But while psilocybin’s effects on humans are becoming well understood, very little is known about why magic mushrooms make it. The assumption has long been that it functions as a chemical defence against fungivores, but the first experimental support appeared only in 2026.
Fruit fly larvae reared on powdered magic mushrooms suffered impaired development and reduced survival, while field studies found that liberty caps - one of the most widespread magic mushroom species - support relatively few arthropod species. Crucially, however, the experiments did not show that psilocybin itself was responsible.
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Any protective effect of psilocybin may have nothing to do with its resemblance to serotonin. When a magic mushroom is damaged - by a grazing animal, for example - enzymes convert psilocybin into highly reactive compounds called psilocyl oligomers.
These stain the damaged tissue blue and may make the mushroom harmful or unpalatable to whatever is eating it. This suggests psilocybin may be a magic mushroom’s way of storing potent chemicals in a harmless form until they are needed.
If psilocybin does have a protective role, it doesn’t seem to be very effective against humans. We don’t avoid psilocybin - we seek it out, to enjoy a biochemical effect that may be entirely incidental to the reason it evolved in the first place.
top image: Psilocybin mushrooms. Credit: Yarphoto/ Getty Images.
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