Matthew Johnson: Psychedelics | Lex Fridman Podcast #145

The following is a conversation with Matthew Johnson, a professor of psychiatry and behavioral science at Johns Hopkins and is one of the top scientists in the world conducting seminal research on psychedelics. This was one of the most eye-opening and fascinating conversations I've ever had on this podcast. I'm sure I'll talk with Matt many more times. A quick mention of the sponsor, followed by some thoughts related to the episode. Thank you to a new sponsor, Brave, a fast browser that feels like Chrome but has more privacy-preserving features. Neuro, the maker of functional sugar-free gum and mints that I use to give my brain a quick caffeine boost. Four Sigmatic, the maker of delicious mushroom coffee. I'm just now realizing how (laughs) ironic this set of sponsors are. And Cash App, the app I use to send money to friends. Please check out these sponsors in the description to get a discount and to support this podcast. As a side note, let me say that psychedelics is an area of study that is fascinating to me in that it gives hints that much of the magic of our experience arises from just a few chemical interactions in the brain and that the nature of that experience can be expanded through the tools of biology, chemistry, physics, neuroscience, and artificial intelligence. The fact that a world-class scientist and researcher like Matt can apply rigor to our study of this mysterious and fascinating topic is exciting to me beyond words, as is the case with any of my colleagues who dare to venture out into the darkness of all that is unknown about the human mind with both an openness of first-principle thinking and the rigor of the scientific method. If you enjoy these things, subscribe on YouTube, review it with five stars on Apple Podcasts, follow on Spotify, support on Patreon, or connect with me on Twitter @lexfridman. And now here's my conversation with Matthew Johnson. Can you give an introduction to psychedelics, like a whirlwind overview? Maybe what are psychedelics and, uh, what are the kinds of psychedelics out there? And in whatever way you find meaningful to categorize.

Yeah. You can categorize them by their chemical structure, so phenethylamines, tryptamines, ergolines. Um, that is, is less of a meaningful way to classify them. I, I think that their pharmacological activity, their receptor activity is the best way. Let me, let me start even broader than that because there I'm talking about the classic psychedelics. So broadly speaking, when we say psychedelic, that refers to, for most people, a broad number of compounds that work in different pharmacological ways. So it includes the so-called classic psychedelics. That includes psilocybin and psilocin, which are in mushrooms, LSD, dimethyltryptamine or DMT, it's in ayahuasca, people can smoke it too, mescaline, which is in peyote and San Pedro cactus. Um, and those all work by hitting a certain, uh, subtype of serotonin receptor, the serotonin 2A receptor. It's, they act as agonists at that receptor. Other compounds like PCP, ketamine, MDMA, ibogaine, they all are, more broadly speaking, called psychedelics, but they work by, uh, very different ways pharmacologically and they have some different effects, including sub- subjective effects, even though there's enough of an overlap in the subjective effects that, you know, people informally refer to them as psychedelic. And I think what that overlap is, you know, compared to, say, you know, caffeine and cocaine and, you know, Ambien, et cetera, um, other psychoactive drugs, is that they have strong effects in altering one's sense of reality and including the sense of self. And I should throw in there that, that cannabis, more historically, like in the '70s, has been called a minor psychedelic. And I think with that latter definition, it, it, it does fit that definition, particularly if one doesn't have a, a tolerance.