What Should We Make Of Sasha Chapin's Claim That Taking LSD Restored His Sense Of Smell After COVID?

https://astralcodexten.substack.com/p/what-should-we-make-of-sasha-chapins   I. Substack blogger Sasha Chapin writes that COVID-19 Took My Sense Of Smell, LSD Brought It Back. He got coronavirus, and like many people lost his sense of smell (medical term: dysosmia or anosmia). Ten days after recovery, he still couldn’t smell anything. He looked on Twitter and found some anecdotal reports that psychedelics had helped with this, so he took LSD and tried to smell some stuff while tripping. He says it “totally worked. Fully and near-instantaneously. Like a light switch turning on.” The details: My idea was that I’d do some scent training while on LSD, to—hand-wavey lay neuroscience incoming—stimulate whatever olfactory neurogenesis might occur. Before tripping, I laid out my fragrance collection, along with a few ingredients from the pantry. All-in-all, there were about fifty things to smell, and, as the LSD started kicking in, I started making my way through the selection. At that moment, my sense of smell was still somewhat there but mostly not. However, something odd was happening; I could detect some of the fragrances’ nuances that I couldn’t pick up earlier that day, and what I detected shifted from moment to moment.  It was like I was listening to a piece of music with random instruments dropping in and out of the mix. This was still a kind of anosmia, but a different kind, and it almost felt as if my olfaction was re-negotiating reality in real time. And then another weird thing happened. For a couple of hours, I got acute short-term parosmia (distorted smell.) My nose felt dry, and a weird puke-y smell filled my mind. According to some research I’d done, in anosmic patients parosmia sometimes precedes recovery, so, though this was quite unpleasant, I felt hopeful that this was some part of the regeneration process. I cleaned the house, my wife took me shopping, we went to Home Depot, and then had dinner. We got home soon after, about seven hours after my trip began, and I returned to my fragrance collection. Cue triumphant music: all of them were now smellable, in high-definition. My anosmia was gone. Moreover, some were more pleasant than before; iris was more palatable to me than it ever had been. This was a moment I won’t soon forget. Some fragrances—especially Dzing!—gave me full-body chills. The next day, my sense of smell was still there, but it fluctuated; it was partial in the morning, then full in the evening. Since then, it’s been back basically 100%. (And the improved understanding of iris has persisted.) The number one explanation for incredible Internet medical stories is always “placebo effect”. Number two is “coincidence”, number three is “they made it up”. All of these top the list for Sasha’s experience too. Still, enough people have said something like this that I think it’s worth trying to figure out if there’s any plausible mechanism. II. Anosmia sucks worse than you would expect. For one thing, smell is linked to taste, so most things taste bad or weird or neutral. For another, it’s correlated with much higher risk of depression, and some preliminary work suggests this could be causal (possible mechanism: the brain is getting fewer forms of stimulation?) Some studies find that exposing rats to very strong scents makes them less depressed; it would be funny if this was how aromatherapy worked in humans. So COVID induced anosmia is actually a serious problem. According to annoying people who refuse to provide useful information, between 3% and 98% of people who get coronavirus lose some sense of smell. A meta-analysis that pools all these studies gives a best estimate of around 40%. Lots of respiratory viruses cause some smell loss when they infect your nasal passages, but coronavirus is worse than usual. Milder cases cause more olfactory problems than more severe cases, suggesting that the immune response is at least as involved as the virus itself. The coronavirus cannot infect neurons directly, but might infect other cells in the nose, including cells which support neurons and help regenerate the olfactory epithelium. About half of COVID patients recover their smell in a few weeks, but some cases linger for up to a year. By the end of a year 95%+ have recovered; given that between 3% - 12% of people have random smell disturbances at any given time anyway, I interpret this latter figure less as “some people never recover” and more as “we reach the point where it’s impossible to distinguish from background problems”. Sasha says he was only ten days in when he took LSD, so this is well inside the window where we would expect him to eventually recover anyway. But it still doesn’t make sense that he recovered within the space of a few hours, or that he felt his smell was stronger than before.