Lysergic acid diethylamide (also known as Lysergide, LSD-25, LSD, L, Lucy, and Acid) is a psychedelic substance of the lysergamide class.[2] LSD is known as one of the most potent, controversial, and widely used psychedelic substances in history. While research suggests that it produces its psychoactive effects by binding to serotonin receptors in the brain, its precise mechanism is not yet understood.

The psychoactive effects of LSD were first discovered in 1943 by the Swiss chemist Albert Hofmann. In the 1950s, it was marketed under the name Delysid and used in psychotherapy and scientific research.[3] LSD garnered widespread interest from clinicians and researchers and was notably secretly investigated by the U.S. Central Intelligence Agency (CIA) as a potential mind control agent.[4] Use of LSD spread widely in the 1960s counterculture which eventually led to its prohibition in 1971.[5][6]

Following a 40 year hiatus, research into LSD’s potential therapeutic uses has seen a resurgence. LSD is currently under investigation for the treatment of a number of ailments including alcoholism, addiction, cluster headache, and anxiety associated with terminal illness.[3] LSD remains in widespread illicit use for recreational and spiritual purposes. The lifetime prevalence of LSD use among adults is in the range of 6-8%.[3]

Characteristic effects of LSD include geometric visual hallucinations, time distortion, enhanced introspection, and ego loss. LSD is commonly described by users to evoke entheogenic and mystical-type experiences that can facilitate self-reflection and personal growth. It is considered by some to be the first modern entheogen, a category which had been limited to traditional plant preparations or extracts.[7]

Unlike other highly prohibited substances, LSD is not considered to be addictive or physiologically toxic.[8][9] Nevertheless, adverse psychological reactions such as severe anxiety, paranoia and psychosis are always possible, particularly among those predisposed to mental illness.[10] It is highly advised to use harm reduction practices if using this substance.