LSD: general

LSD (lysergic acid diethylamide) is a potent synthetic hallucinogen derived from ergot alkaloids [1], first synthesised by Albert Hofmann [2][3] in 1938 [4][3], with its psychoactive effects discovered in 1943 [4] when Hofmann accidentally ingested a small amount and described the first "trip" [3][5]. It works by binding to serotonin receptors, which produces its psychedelic effects [5].

It is described as one of the most potent psychoactive drugs known [3]. For LSD, as for psilocybin, no dose has been established above which life is known to be endangered [6], and overdose deaths from pure psychedelics are extremely rare, typically involving very large doses or mixing with other substances [7]. That does not mean it is safe: the experience itself can be difficult, and is often described as challenging and sometimes traumatic [8]. Across psychedelics as a class, taking a very high dose increases the likelihood of a distressing experience [9]. Set and setting — your mental state and physical environment going in — are, for psychedelics as a class, critical determinants of how an experience unfolds [6], and having a sober sitter present is also considered important for safety [9].

LSD has been studied clinically, including in psychiatric research and psycholytic and psychedelic therapy in the 1950s and 60s [4][3], and more recently for cluster headache, in the terminally ill, and as a tool for studying consciousness [4]. None of this amounts to approved medical use: it is not an approved drug [1], has no current medical use [3], and no approved indications for LSD-assisted therapy exist today [2]. Evidence that it can work as treatment with manageable risk comes from controlled clinical settings only, not from how people typically use it outside research [8]. Reported physical risk relative to some other common drugs, including alcohol, is lower [8] — but that is a statement about physical harm specifically, not a statement that using LSD carries no risk at all.

References

1. LSD | Definition, Psychological Effects, & Ergot Fungus | Britannica — Encyclopædia Britannica
2. Lysergic Acid Diethylamide (LSD) (Archived) — National Center for Biotechnology Information (NCBI)
3. Lysergide (LSD) drug profile | The European Union Drugs Agency (EUDA) — European Union Drugs Agency
4. The pharmacology of lysergic acid diethylamide: a review — PubMed (National Library of Medicine)
5. LSD - American Chemical Society — American Chemical Society
6. Hofmann vs. Paracelsus: Do Psychedelics Defy the Basics of Toxicology?—A Systematic Review — PMC / National Library of Medicine
7. Adverse effects of psychedelics: From anecdotes and misinformation to systematic science — Journal of Psychopharmacology
8. LSD | Drug Science — Drug Science UK
9. Understanding Risk in the use of Psychedelics — UC Berkeley Center for the Science of Psychedelics