Short answers, pulled from the story.
Psychedelics are a subclass of hallucinogenic drugs that trigger non-ordinary mental states by binding to and activating the serotonin 5-HT2A receptor. The intensity of their hallucinogenic effects is directly correlated with the level of 5-HT2A receptor occupancy, as measured by positron emission tomography imaging. Blocking this receptor with drugs like ketanserin or risperidone can abolish the effects entirely.
Swiss chemist Albert Hofmann synthesized LSD in 1938 at Sandoz Laboratories while developing drugs from ergot. He accidentally discovered its hallucinogenic effects in 1943 when minute amounts absorbed through his skin, and conducted a deliberate self-experiment on April 19 of that year, which became the psychedelic holiday Bicycle Day. Sandoz began distributing LSD for research under the brand name Delysid in 1949.
The earliest archaeological evidence of psychedelic plant and fungi use by humans dates back roughly 10,000 years. Peyote has been used for several thousand years in the Rio Grande Valley, and the San Pedro cactus has archaeological evidence of use going back two thousand years through Moche, Nazca, and Chavín cultures.
Most psychedelics fall into one of three chemical families: tryptamines, phenethylamines, or lysergamides. Major examples include LSD (a lysergamide), psilocybin (a tryptamine found in hundreds of mushroom species), mescaline (a phenethylamine found in peyote and the San Pedro cactus), and DMT (a tryptamine found in various plants and used in ayahuasca). Some research suggests there may be more than 100,000 unique possible serotonergic psychedelics.
Psilocybin and LSD are legally approved or used under special access programs in countries including Australia, Switzerland, Canada, and Israel for conditions such as treatment-resistant depression. The U.S. Food and Drug Administration has granted breakthrough therapy status to psilocybin for treatment-resistant depression and major depressive disorder. Research is also examining proposed psychedelic therapies for major depressive disorder and anxiety linked to terminal illness.
A 2023 international survey found 14% of respondents felt more anxious for an extended period after using a psychedelic. In a survey of 608 people who reported post-psychedelic difficulties, one third said the difficulties lasted longer than a year. Reported effects include anxiety, derealization, social isolation, visual distortions, and existential confusion. Psychedelics can also induce hypomania or mania in people with bipolar disorder, with a clinically meaningful incidence of 5.8% in clinical trials and 30% in naturalistic settings.