Lysergic acid diethylamide, commonly known as LSD, and known colloquially as acid or lucy is a potent psychedelic drug. Effects typically include intensified thoughts, emotions, and sensory perception. At sufficiently high dosages LSD manifests primarily mental, visual, and auditory hallucinations LSD is a hallucinogenic drug that can change your perception of reality. Find out how LSD works, and the health risks of LSD addiction.LSD or ‘acid’ is a powerful hallucinogenic drug. Time, movement, color and sound can appear different depending on the ‘trip’. Find out more from FRANK.

Official Name

​Lysergic Acid Diethylamide (LSD)

Street Name

LSD, acid, blotter, microdot, window pane

What is it?

LSD (lysergic acid diethylamide) is a potent hallucinogen—that is, a drug that can alter a person’s perception of reality and vividly distort the senses. LSD was originally derived from “ergot,” a fungus that grows on rye and other grains.

The hallucinogenic effect of LSD was first discovered in 1943 by Dr. Albert Hofmann, a Swiss research chemist working at a pharmaceutical company. Early studies exploring potential use of the drug focused on what insight it might offer into certain kinds of mental illness. In the 1950s, intellectuals such as Aldous Huxley experimented with the drug for its alleged ability to induce a state of “cosmic consciousness.”

LSD was the subject of numerous research studies in the 1950s and early 1960s. These studies included investigating the therapeutic potential of the “psychedelic” experience in treating chronic alcoholism and mental illness, and in helping patients with terminal illnesses to accept death. LSD also captured the attention of the CIA, who tested its potential for use in psychological warfare.

Recreational use of LSD increased in the 1960s as its “mind-expanding” qualities were promoted by influential role models such as Harvard scientist Timothy Leary and novelist Ken Kesey.

Concerns about the possible long-term effects of LSD led to new laws aimed at restricting its use. The sale, possession for the purpose of selling, and distribution of LSD were first made punishable in Canada in 1962. LSD currently has no medical use, and is prohibited under Schedule III of Canada’s Controlled Drugs and Substances Act.

Where does it come from?

Most LSD is produced in illegal laboratories, with only a very small amount legally manufactured for use in research.

What does it look like?

Pure LSD is a white, crystalline powder that dissolves in water. It is odourless and has a slightly bitter taste. An effective dose of the pure drug is too small to see (20 to 80 micrograms). LSD is usually packaged in squares of LSD-soaked paper (“blotters”), miniature powder pellets (“microdots”) or gelatin chips (“window pane”). Blotters are sometimes printed with illustrations of cartoon characters.

Who uses it?

People who use LSD range from those seeking a high to those seeking a mystical experience. The incidence of LSD use reached its peak during the 1960s and 1970s, and was closely associated with the “hippie” youth culture of that time. Rates of LSD use dropped in the 1980s, rose again in the 1990s, and have since dropped back down to low levels. The use of LSD among Ontario students in grades 7 to 12 dropped from 6.8 per cent in 1999 to 1.8 per cent in 2009.

How does it make you feel?

LSD is usually taken by mouth and held on the tongue or swallowed, but there have been reports of it being inhaled or injected.

How LSD affects you depends on several things:

  • your age
  • how sensitive you are to the drug
  • how much you take and how often you take it
  • how long you’ve been taking it
  • the method you use to take the drug
  • the environment you’re in
  • whether or not you have certain pre-existing medical or psychiatric conditions
  • whether you’ve taken any alcohol or other drugs (illegal, prescription, over-the-counter or herbal).

The physical effects of LSD may include numbness, rapid heartbeat, reduced co-ordination, chills, nausea, tremor, weakness and dilated pupils. Sensations of gravity may be altered, ranging from feeling weighted down, to feeling light and floating. The LSD experience, usually referred to as a “trip,” varies widely and is unpredictable. Individual reactions to the drug can range from ecstasy to terror, even within a single drug-taking experience. People who have used the drug before, and had a positive experience, may have a negative experience if they take it again.

Two factors that influence the way people feel when they take LSD are their “mindset”—their expectations, experience and mood at the time they take the drug—and the setting, or place where they are. For those who use the drug, the possibility of an adverse reaction, or “bad trip,” may be reduced by taking the drug only when already in a positive state of mind, in a relaxed environment and with supportive friends.

LSD produces vivid visual effects. Colours seem to become more intense, halos or rainbows may appear around objects, and shapes may become fluid in form. Rapidly changing brightly coloured geometric patterns and other images may be seen, whether the eyes are open or shut. These visual distortions are referred to as “pseudo-hallucinations” because people know that what they are seeing is not real and is due to the effect of the drug. True hallucinations, where people believe that what they are seeing is real, are not as common, but they can occur and can be frightening.

LSD affects your senses, mood, thoughts and how you perceive yourself and the world around you. The drug can produce a wide spectrum of mental states, from a sense of joy, wonder and heightened sensitivity, to panic, confusion and anxiety. Thoughts may seem clear and profound or race rapidly without logic. Sense of time, distance and body image may be distorted. Boundaries between the self and the outside world may seem to dissolve. Some users report a fusion of the senses; for example, “seeing” music or “hearing” colour.

How long does the feeling last?

The effects of LSD come on gradually within an hour of taking the drug, peak at two to four hours and gradually taper off, with the entire trip lasting up to 12 hours. The intensity of the effect depends on the size of the dose.

Some users feel let down or fatigued for 12 to 24 hours after the trip is over.

Is it addictive?

Yes, it can be addictive. Some people who use LSD repeatedly feel compelled to take it. The drug takes on an exaggerated importance in their lives, leading to emotional and lifestyle problems.

People who use LSD regularly do not experience physical withdrawal symptoms when they stop taking the drug. However, regular use of LSD will produce “tolerance” to the effects of the drug. This means that if LSD is taken repeatedly over a period of several days, it no longer has the same effect. After several days of not taking the drug, it becomes effective once again.

Is it dangerous?

It can be.

Sometimes people who take the drug feel that the experience gets out of control. They may feel they are losing their identity or are disintegrating into nothingness. Such a reaction can lead to a state of panic. They may try to flee the situation, or become paranoid and frightful and lash out at the people around them. People experiencing a dangerous reaction to LSD should be kept as calm as possible. If their distress continues, they should receive treatment at a hospital emergency room.

No deaths resulting exclusively from an overdose of LSD have been reported. However, LSD affects judgment, which can lead to irrational, sometimes dangerous, behaviour. The drug has made people feel that they could fly, or that they could walk through traffic and this has resulted in accidental injuries and deaths. In some people, LSD may release underlying psychosis or aggravate anxiety or depression. Long-term psychological problems may follow a bad trip with LSD. Taking only a small amount, or low dose, of LSD may not reduce the possibility of having a negative reaction. One person may have a bad trip on a low dose, while another may take a high dose and get through it without distress. Higher doses do, however, increase the hallucinogenic effect of the drug.

Because LSD is produced illegally, it varies in purity and strength. If you take LSD, you can’t be sure exactly what or how much you are taking, or how it will affect you.

Because LSD profoundly alters perception, it is highly hazardous to drive a vehicle while under the drug’s influence.

What are the long-term effects of using it?

The use of LSD can result in long-term effects for both one-time and regular users of the drug. Possible negative effects are “flashbacks” of the drug experience, as well as prolonged anxiety, depression or psychosis. These reactions usually decrease over time, and end within a few months after LSD was last taken, but may continue for years.

Flashbacks are the spontaneous and unpredictable replay of an aspect of the LSD trip, occurring some time after the initial effects of the drug have worn off. Visual or emotional experiences that were originally seen or felt while under the influence of LSD are re-experienced. Flashbacks usually last only a few seconds or minutes, but may happen over and over again. Only some people who take LSD have flashbacks, but frequent users of the drug are said to be at greater risk. Flashbacks may be triggered by smoking marijuana <see “marijuana” in related links section> or drinking alcohol <see “alcohol” in related links section>, or by emotional stress or fatigue.

Depression or anxiety may follow a bad trip. Psychosis may develop after using LSD, although it is thought that this reaction may be more likely to occur in people with latent, or underlying, mental health problems.

Copyright © 2001, 2010 Centre for Addiction and Mental Health

Where can I find help, treatment and support?

Where can I find more information?

LSD: a new treatment emerging from the past

Psychedelics fell from medical grace nearly half a century ago, but recent activity suggests that some researchers have “high hopes” for their return.1,2 Over 60 years ago, Albert Hofmann at Sandoz Pharmaceutical Laboratories in Switzerland first synthesized lysergic acid diethylamide (LSD) and personally experienced its effects (later described as a voyage into madness or a chemically induced psychosis) in 1943. Hofmann’s drug opened up a new era of hallucinogenic research. Over the next 15 years, more than a thousand articles on the use of LSD appeared in medical and scientific publications. In 1957, that work gave rise to the term “psychedelic” to describe a mind-manifesting response, described by some as an experience that brought to light matters that had previously been part of the unconscious.

During the 1950s and into the early 1960s, LSD was used rather successfully to treat alcoholism, arguably by compressing years of psychotherapy into a single, intensive, self-reflective session that helped patients with alcohol dependence achieve a new self-image and the willpower to move beyond their disease. Others explored LSD as an adjuvant to psychotherapy for addressing trauma; still others used it to model psychosis and to generate interest in studying schizophrenia as a chemical reaction in the brain. However promising these studies were, they also invited critics who argued that LSD did not perform well in randomized controlled trials, that the drug was too enticing as a substance for abuse or that it was an altogether dangerous substance given its capacity for conjuring terrifying hallucinations or producing psychosis.

By the mid-1960s, however, scientific criticism was somewhat moot. Research into LSD came to a decided halt, largely because it had become synonymous with countercultural activities, hedonism and drug abuse. By the end of that colourful decade, LSD was considered in many jurisdictions as a prohibited substance, and its clinical applications were moved to the margins of acceptable medicine.3

An external file that holds a picture, illustration, etc.
Object name is 1871079f1.jpg

Image courtesy of Ekaterina Kovyleva/Hemera/Thinkstock

Over the past few years, that situation has started to change. A new generation of researchers has taken up the torch with a goal of resurrecting the psychedelic science of the 1950s, particularly along the paths of addiction research and palliative care. Will this new group of enthusiasts be more nimble, or have cultural circumstances changed sufficiently to embrace psychedelics anew?

Historians are not good at predicting the future, so I won’t; we are trained, however, to examine social context and change over time, which is useful for identifying trends and assigning causality, with hindsight on our side. The incarnation of psychedelic research in the 21st century resurrects some of the old hypotheses and explores some of the same applications that clinicians experimented with 50 years ago. On the surface, the psychedelic renaissance might be dismissed for retreading familiar ground. A deeper look at the cultural context suggests that psychedelic drug research in the 21st century may have changed enough to warrant a retrial.

Neuroscience was in its infancy in the 1950s when LSD researchers first postulated that receptors were involved in regulating psychotic symptoms, among other things. Reactions to LSD seemed to suggest that areas of the brain could be turned on and off, or that different levels of consciousness could be activated through the use of chemicals. Yet the prohibition of LSD and its psychedelic cousins was not simply the result of unsophisticated science; drug regulators played a role in squeezing them out of legitimate existence based on assumptions about their perceived dangers, adverse effects and appetite for abuse.

In Canada, the story of LSD’s regulation is particularly revealing. The issue first arose in 1962 amid the thalidomide scandal. As regulators discussed the appropriate schedule for thalidomide, they paused to consider whether LSD should be placed under similar restrictions. The medical community at that moment banded together to defend the prerogative of clinicians to set the criteria for determining the efficacy of a drug. A few years later, under pressure from the Senate led by Senator Hartland Molson of the Molson Brewery family, physicians yielded to the recommendations of policymakers.4 Suffice to say, the leading therapeutic application was using LSD to treat alcoholism, and Senator Molson pushed the law forward, while the brewing industry enjoyed regulations that helped bring beer to market.

The bureaucracy of drug regulation has grown exponentially over the past half century and has recently come under criticism for making political rather than evidence-based decisions. In 2007, British pharmacologist David Nutt published a harm-ranking scale in The Lancet, where he argued that psychedelic drugs were much less harmful than the regulated substances of nicotine and alcohol.5 He was later fired from his position on the Advisory Council on the Misuse of Drugs, which catapulted him into the debates over renewing medical research on psychedelics. He subsequently pointed to the gulf that has grown between clinical drug trials and government regulations, lamenting the “daunting bureaucratic labyrinth that can dissuade even the most committed investigator.”6

Liberal regulation may contribute to hyperbolic scientific claims and overzealous research agendas, but tight regulatory controls may quash potential therapies or the development of basic scientific information. Regulation has come to represent a degree of safety and reduced liability that facilitates getting a drug to market, rather than setting the research parameters for a novel substance or a novel application.79 Does this imply that scientists and drug regulators will find themselves at cross-purposes? A 21st century resurgence of psychedelic research suggests this may be the case.

Evidence is mounting that a new era of psychedelic medicine may be around the corner. Laboratories in the United States and Europe have already been conducting trials for several years. The historical context may have changed to permit these experiments, but who will champion this next phase of psychedelic science? In 1963, Aldous Huxley received LSD on his death bed and suggested that its effects bathed him in a vision of warmth and spiritual belonging, such that he could face death without fear. Palliative care has been an area identified for the potential use of psychedelics for precisely this reason; not as a treatment, but as a psychological therapy that helps people face death. Will the growing need for palliation change the context sufficiently to warrant a second look at LSD clinically? As baby boomers age, placing greater demands on end-of-life care than we have faced in the past, will they again tip the demographic scales and create sufficient patient demand for LSD?

Go to:


Funding: This project was funded by a grant from the Social Sciences and Humanities Research Council and a salary award through the Canada Research Chair in the History of Medicine (Tier 2). The funding had no direct impact on the author’s research or conclusions.

Go to:


1. Langlitz N. Neuropsychedelia: the revival of hallucinogen research since the decade of the brain. Berkley. Oakland (CA): University of California Press; 2013. [Google Scholar]

2. Kupferschmidt K. High hopes. Science 2014;345: 18–23. [PubMed] [Google Scholar]

3. Oram M. Efficacy and enlightenment: LSD psychotherapy and the drug amendments of 1962. J Hist Med Allied Sci 2014;69:221–50. [PubMed] [Google Scholar]

4. Dyck E. Just say know? Criminalizing LSD and the politics of psychedelic expertise, 1961–1968. In: Montigny E, editor. The real dope. Toronto: University of Toronto Press; 2011:169–96. [Google Scholar]

5. Nutt D1, King LA, Saulsbury W, et al. Development of a rational scale to assess the harm of drugs of potential misuse. Lancet 2007;369:1047–53. [PubMed] [Google Scholar]

6. Editors. End the ban on psychoactive drug research. Sci Am 2014;310(2):33 Available: www.scientificamerican.com/article/end-the-ban-on-psychoactive-drug-research/ (accessed 2015 Apr. 2). [Google Scholar]

7. Marks H. The progress of experiment: science and therapeutic reform in the United States, 1900–1990. Cambridge (MA): Cambridge University Press; 1997. [PMC free article] [PubMed] [Google Scholar]

8. Healy D. Let them eat Prozac: the unhealthy relationship between the pharmaceutical industry and depression. New York: New York University Press; 2004. [Google Scholar]

9. DeGrandpre R. The cult of pharmacology: how America became the world’s most troubled drug culture. Durham (NC): Duke University Press; 2006. [Google Scholar]

Leave a Comment

Your email address will not be published. Required fields are marked *

Shopping Cart
    Your Cart
    Your cart is emptyReturn to Shop