The Not-So-Trippy Reason Mushrooms Are Psychedelic

(Inside Science) -- There are about 10,000 known species of mushrooms in the world, and most scientists agree that there are many more that haven’t even been discovered. Given all those different types of mushrooms, there’s actually only a few hundred on the planet that produce a chemical that causes hallucinations. But the mushrooms didn’t develop their “trippy” properties just to make people high. Scientists say it’s to trick fungi-eating insects.

Jason Slot from the Department of Plant Pathology at Ohio State University said, “There’s actually only a very small number of mushrooms, about 200 across the globe, that produce this substance called psilocybin that causes hallucinations. A lot of their close relatives do not make this substance at all, and we’re interested in how it is that fungi are able to be hallucinogenic.”

Psilocybin is a naturally occurring psychedelic compound found in some mushrooms. It interacts with certain receptors in the brain.

“So, the question of magic mushrooms is a very old one, but it’s also one where the science has been slowed down due to regulatory restrictions on possession of psilocybin or mushrooms. Because of that, there are some very basic unanswered questions, such as how do mushrooms even make psilocybin? In order to address this question, my lab compares the genes and the genomes of different species of fungi, different species of mushrooms. And through that process, we’re able to identify certain genes that are only found in the magic mushrooms.

“By analyzing the evolution of those genes, we were able to determine that these genes are evolving in a very specific kind of environment of decaying wood and animal manure. And in that environment of animal manure, it appears that certain mushrooms were able to take those genes from other mushrooms and thus become magic themselves. So, this is a phenomenon called horizontal gene transfer and it’s very well-known in bacteria,” said Slot.

Scientists now know that some mushrooms took on the hallucinogenic genes from other mushrooms, but why? What natural advantage do the mushrooms get from making psilocybin?

“We don’t think that mushrooms became magic in order to get humans intoxicated. We think that probably insects are the more likely targets of these compounds. Psilocybin, for instance, directly interacts with the nervous system of insects. We think probably the main effect would be to reduce the feeding, and there is evidence that if you stimulate the same receptors that psilocybin affects in the brains, in the nervous systems of insects, it slows down their feeding,” said Slot.

The bottom line -- if the ’shrooms don’t appeal to insects, they can flourish in the environment.

“The interesting thing about this sort of work is that we’re able to learn about different ways that fungi are able to interact with their environment. And not only how they interact with their environment, but how those ways came to be through evolutionary history,” concluded Slot.