Lysergic acid diethylamide, commonly known as LSD (from German ) and by the nicknames acid and Lucy, is a semisynthetic psychedelic drug derived from ergot, known for its potent psychological effects.
LSD taken orally has an onset of action of 0.4 to 1.0hours and a duration of 7 to 12hours. In recreational settings it is commonly administered via tabs of blotter paper. LSD is extremely potent, with noticeable effects at doses as low as 20micrograms and is sometimes taken in even smaller amounts for microdosing. Despite widespread use, no fatal human overdoses have been documented. LSD is mainly used recreationally or for spiritual purposes. LSD can cause mystical experiences. LSD exerts its effects primarily through high-affinity binding to several serotonin receptors, especially the serotonin 5-HT2A receptor, and to a lesser extent dopamine and adrenergic receptors. Neuroimaging studies indicate that LSD reduces the efficacy of thalamo-cortical information filtering (producing sensory overload), decreases oscillatory power within the default mode network, and flattens hierarchical organization of large-brain activity. At higher doses, it can induce visual and auditory hallucinations, ego dissolution, and anxiety. LSD use can cause hallucinogen-induced psychotic disorder where paranoia and delusions persist beyond the initial effects of the drug. LSD may lead to persistent visual disturbances known as hallucinogen persisting perception disorder (HPPD).
Swiss chemist Albert Hofmann first synthesized LSD in 1938 and discovered its potent psychedelic effects in 1943 after accidental ingestion. It became widely studied in the 1950s and 1960s. The drug was initially explored for psychiatric use due to its structural similarity to serotonin and safety profile. It was used experimentally in psychiatry for treating alcoholism and schizophrenia. By the mid-1960s, LSD became central to the youth counterculture in places like San Francisco and London, influencing art, music, and social movements through events like Acid Tests and figures such as Timothy Leary, Owsley Stanley and Michael Hollingshead. Its psychedelic effects inspired distinct visual art styles and musical innovations, and caused a lasting cultural impact. However, its association with the counterculture movement of the 1960s led to its classification as a Schedule I drug in the United States in 1970. It was also listed as a Schedule I controlled substance by the United Nations in 1971 and remains without approved medical uses.
Despite its legal restrictions, LSD remains influential in scientific and cultural contexts. Research on LSD declined due to cultural controversies by the 1960s, but has resurged since 2009. In 2024, the United States Food and Drug Administration designated LSD (code name MM120 or DT120) as a breakthrough therapy for generalized anxiety disorder. As of 2017, about 10% of people in the United States had used LSD at some point, with 0.7% having used it in the past year. Usage rates have risen, with a 56.4% increase in adult use in the United States from 2015 to 2018.
Uses Recreational LSD is commonly used as a recreational drug for its psychedelic effects.
Spiritual LSD can catalyze intense spiritual experiences and is thus considered an entheogen. Some users have reported out of body experiences. In 1966, Timothy Leary established the League for Spiritual Discovery with LSD as its sacrament.San Francisco Chronicle September 20, 1966 Page One Stanislav Grof has written that religious and mystical experiences observed during LSD sessions appear similar to descriptions in sacred scriptures of great religions of the world and the texts of ancient civilizations.
Medical
In Switzerland, a special authorization program allows limited medical use of substances like LSD for patients with serious, treatment-resistant conditions, with patients treated under physician supervision.
Dosing
LSD is an extraordinarily potent substance, and is one of the most potent psychoactive drugs known. This means that it produces its pharmacological effects at very small doses, with its dose range measured in micrograms (μg); that is, millionths of a gram. Noticeable effects can occur with doses of LSD as low as 20μg, which is around 1/200th the mass of a grain of sand. LSD is approximately 200times as potent as psilocybin and 5,000times as potent as mescaline, meaning that it produces effects of similar magnitude at 1/200 and 1/5,000 times the respective doses.
The usual dose range of LSD for psychedelic effects is 20 to 200μg. The typical intermediate and "good effect" dose for a psychedelic experience is 100μg (range 75–150μg, while 20 to 50μg is a low or "minidose" and 200μg is a high or ego-dissolution dose.) A dose range as wide as 10 to 450μg has been reported. LSD may also be used in microdosing. In this context, it may be used at subthreshold or microdoses of less than 10μg.
The extremely high potency of LSD played an essential role in its emergence and popularity during the counterculture of the 1960s due to the economic feasibility of its manufacture, in contrast to the case of mescaline, which had been known for many decades previously but remained relatively little-known.
The doses of LSD present in illicit LSD samples have decreased over time. In the mid-1960s, Owsley Stanley, the most important black market LSD manufacturer in the United States, distributed LSD at a standard concentration of 270μg, while street samples of the 1970s contained 30 to 300μg. By the 1980s, the amount had reduced to between 100 and 125μg, dropping more in the 1990s to the 20 to 80μg range, and even further in the 2000s.
Effects LSD produces a variety of physical, psychological, and sensory effects.
Psychological The primary immediate psychological effects of LSD are visual pseudo-hallucinations and altered thought, often referred to as "trips". These sensory alterations are considered pseudohallucinations because the subject does not perceive the patterns seen as being located in three-dimensional space outside the body. LSD is not considered addictive. An "afterglow" effect, characterized by an improved mood or perceived mental state, may persist for days or weeks following ingestion. Positive experiences, or "good trips", are described as intensely pleasurable and can include feelings of joy, euphoria, an increased appreciation for life, decreased anxiety, a sense of spiritual enlightenment, and a feeling of interconnectedness with the universe.
Negative experiences, commonly known as "bad trips", can induce feelings of fear, agitation, anxiety, panic, and paranoia. While the occurrence of a bad trip is unpredictable, factors such as mood, surroundings, sleep, hydration, and social setting, collectively referred to as "set and setting", can influence the risk and are considered important in minimizing the likelihood of a negative experience.
Uniquely among psychedelics, LSD appears to have two temporally and qualitatively distinct phases of psychoactive effects. These include an initial psychedelic phase associated with serotonin 5-HT2A receptor agonism and a subsequent paranoia- and psychosis-like phase associated with dopamine D2-like receptor agonism. Subsequent research has found that the delayed dopaminergic phase is associated with the highly potent dopamine D4 receptor agonism of LSD's metabolite 13-hydroxy-LSD. The first phase is described as a "psychedelic experience", with "meaningfulness and portentousness" as the primary effects, while the latter phase is "clearly a paranoid state", including feeling "at the least self-centered, and usually suspicious, with ideas of reference or even paranoid convictions". The second phase typically develops about 4 to 6hours after administration but at times up to 10hours after administration. Parallels have been drawn between this phase and amphetamine psychosis. There is no indication that similar effects occur with other psychedelics like phenethylamines and simple tryptamines, which lack dopamine receptor agonism. The preceding findings have been described by researchers like Daniel X. Freedman and David E. Nichols.
Sensory LSD induces an animated sensory experience affecting senses, emotions, memories, time, and awareness. The effects range from subtle perceptual changes to profound cognitive shifts. Alterations in auditory and visual perception are common.
Users may experience enhanced visual phenomena, such as vibrant colors, objects appearing to morph, ripple, or move, and geometric patterns on various surfaces. Changes in the perception of food's texture and taste are also noted, sometimes leading to aversion towards certain foods.
There are reports of inanimate objects appearing animated, with static objects seeming to move in additional spatial dimensions. The auditory effects of LSD may include echo-like distortions of sounds, and an intensified experience of music. Basic visual effects often resemble phosphenes and can be influenced by concentration, thoughts, emotions, or music. Higher doses can lead to more intense sensory perception alterations, including synesthesia, perception of additional dimensions, and temporary dissociation.
Physical
LSD can induce physical effects such as pupil dilation, decreased appetite, increased sweating, and wakefulness. The physical reactions to LSD vary greatly, and some may be a result of its psychological effects. Commonly observed symptoms include increased body temperature, blood sugar, and heart rate, as well as goose bumps, jaw clenching, dry mouth, and hyperreflexia. In cases of adverse reactions, users may experience numbness, weakness, nausea, and tremors.
Onset and duration The psychoactive effects of LSD last on average between 7 and 11hours, with a possible range of 4 to 22hours. Higher doses tend to lead to a longer duration of action. The onset of action when administered orally is 0.4 to 1.0hours on average, with a possible range of 0.1 to 1.8hours. The time to peak effects given orally is 2.2 to 2.8hours on average, with a range of 1.3 to 6.5hours.
The duration of LSD can be shortened through the use of trip killers or shorteners like ketanserin. In a clinical trial, ketanserin given 1hour after LSD shortened its duration from 8.5hours to 3.5hours or by about 60%.
Contraindications
Adverse effects
LSD, a classical psychedelic, is deemed physiologically safe at standard doses (50–200 μg), and its primary risks lie in psychological effects rather than physiological harm. A 2010 study by David Nutt ranked LSD as significantly less harmful than alcohol, placing it near the bottom of a list assessing the harm of 20 drugs.
Psychological effects LSD can induce panic attacks or extreme anxiety, colloquially termed a "bad trip". Despite lower rates of depression and substance abuse found in psychedelic drug users compared to controls, LSD presents a heightened a risk of hallucinogen-induced psychotic disorder for individuals with mental illnesses such as bipolar disorder or schizophrenia or who have a family history of those illnesses. It is common for people with pre-existing mental illness to be hospitalized for hallucinogen-induced psychotic disorder caused by LSD. LSD is also the main cause of hallucinogen persisting perception disorder (HPPD), where visual distortions persist beyond the initial effects of the drug.
Suggestibility While research from the 1960s indicated increased suggestibility under the influence of LSD among both mentally ill and healthy individuals, the CIA and US Department of Defense conducted secret mind control experiments in which LSD was administered to unwitting human subjects as part of secret operations MKUltra and Operation Midnight Climax.
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