Psychedelics

by

Erika Dyck

• LAST MODIFIED: 17 April 2025
• DOI: 10.1093/obo/9780197768723-0019

Introduction

The term psychedelic was formally introduced in 1957 to mean “mind manifesting” or “to bring to light,” but the phenomenon of seeking nonordinary states of consciousness has long and diverse roots. Psychedelic substances are associated with plants, fungi, animals, and synthetic substances that can cause changes in consciousness and hallucinations. These substances are found all over the world; some common examples include peyote cacti (containing the alkaloid mescaline), d-lysergic acid diethylamide (LSD, synthesized from ergot fungus), psilocybin “magic” mushrooms, ayahuasca (containing N,N-dimethyltryptamine [DMT]), ibogaine, and 3,4-Methylenedioxymethamphetamine (MDMA, commonly called Ecstasy or Molly). Psychedelics have been part of spiritual and healing ceremonies in many parts of the world for centuries and even millennia, incorporated into Indigenous practices and rituals. Throughout the twentieth century, pharmacologists and psychiatrists sought to examine the therapeutic potential of these “madness-mimicking” substances, also called hallucinogens to emphasize their visual and perceptual effects, believing that they may provide insight into madness or serve as a temporary conscious-expanding opportunity through self-experimentation to gain personal insight into pathological conditions. Psychedelic therapies showed early promise especially in areas of addiction, and in disorders associated with trauma. Despite their potential, researchers struggled to reach a consensus on how psychedelics should be used in therapy, finding instead that psychedelic sessions relied significantly on “set and setting”—a person’s mindset or attitude toward the experience along with its environmental, contextual, and social aspects. These extra-pharmacological factors complicated a more systematized approach to studying psychedelics, such as evaluating them in randomized controlled trials (RCTs), which became a gold standard in pharmacological research in the 1960s. Beyond the psychiatrist’s couch and the secret CIA files of MKULTRA, nonaddictive, consciousness-expanding experiences inspired adventurous and creative types, from philosophers to musicians and artists, and by the late 1960s a psychedelic cultural phenomenon transformed their association from spiritual guides or medicines to recreational drugs and countercultural catalysts. The concept of “psychedelic” itself expanded from a class of pharmacological substances to an idea, an aesthetic, and even an attitude to society and life. In the United States especially, authorities came to associate psychedelics with nonordinary ways of being, in terms of sexuality, communal living, fashion, and increasingly anti-establishment political perspectives. Throughout the 1960s, several political jurisdictions criminalized psychedelics, and in 1971 the United Nations introduced a new set of drug schedules that classified psychedelics in Schedule I: substances with a high potential for harm or addiction with no medical value. In the twenty-first century, researchers across clinical and cultural disciplines have questioned the categorization of psychedelics in Schedule I. Dubbed a “psychedelic renaissance,” researchers and civilians alike continue to insist that these substances warrant a retrial. The retrial is largely being narrated in biomedical publications, which is the scope of this entry.

General Overviews

Osmond 1957 formally introduced the word psychedelic in a pivotal paper on psychotomimetic or “madness mimicking” agents. Bisbee, et al. 2018 traces the origins of Osmond’s coinage in his correspondence with Aldous Huxley. Hoffer and Osmond 1967 is a comprehensive guide to the pharmacological and cultural understandings of the growing field of psychedelics. Similarly, Masters and Houston 1966 is an early comprehensive study of psychedelics just as they became prohibited in California. This work joined the growing field of hallucinogenic ethnobotany, including catalogues like Schultes and Smith 1976, part of the Golden Guide series for young readers. Teaming up with pioneering psychedelic chemist Albert Hofmann, Schultes, et al. 1979 is an illustrated guide to the chemical, botanical, and cultural history of psychedelic plants. Meanwhile, Leary, et al. 1964 takes inspiration from the authors’ experiences in Mexico with psilocybin mushrooms and a desire to link these nonordinary states of consciousness with Eastern religions. While Weil and Rosen 1993 criticizes this development in psychedelic approaches, Stafford 1977 combines these ethnobotanical and mystical threads in a wide-ranging study of psychedelics that appeared during the Prohibition era, making it an underground treasure for securing information about the diverse ways to know and identify psychedelics. Aimed at a niche readership that avoided more overt countercultural themes, chemists began producing studies of psychedelic chemistry; chief among these publications were the now landmark pair of volumes by Alexander and Ann Shulgin (see Shulgin and Shulgin 1991). in some circles considered the “bibles” of modern psychedelic chemistry. Perrine 1996 provides an informative panoramic survey of psychoactive drugs that discusses both the culture and chemistry of psychedelic substances. Rätsch 2005 synthesizes a vast amount of ethnobotanical literature to offer a rich botanical, ceremonial, and chemical compendium, including acknowledging the field of entheogens or plant spirit teachers, a concept preferred by ethnobotanists, including Schultes, Wasson, and Ott.

• Bisbee, Cynthia Carson, Paul Bisbee, Erika Dyck, Patrick Farrell, James Sexton, and James W. Spisak. Psychedelic Prophets: The Letters of Aldous Huxley and Humphry Osmond. Montreal: McGill-Queen’s University Press, 2018.

  DOI: 10.1515/9780773556027

  The full correspondence between Huxley and Osmond, whose collaboration and friendship played a seminal role in the early psychedelic era. Both men were broadly involved in psychedelic developments and networks, and their letters stand as an important document in the first wave of psychedelic activity, not least in their coinage of the term itself.

• Hoffer, Abram, and Humphry Osmond. The Hallucinogens. New York: Academic Press, 1967.

  Longtime collaborators Osmond and biochemist and psychiatrist Abram Hoffer coauthored this volume aimed at a range of specialists on hallucinogenic drugs, “one of the major advances of this century.” Surveying up-to-date research on the major psychedelics, they also provide an extensive overview of their “adrenochrome hypothesis,” an early theory of neurochemistry eclipsed by the neurotransmitter model.

• Leary, Timothy, Ralph Metzner, and Richard Alpert. The Psychedelic Experience: A Manual Based on the Tibetan Book of the Dead. New York: University Books, 1964.

  After studying psilocybin mushrooms in Mexico, authors Timothy Leary, Ralph Metzner, and Richard Albert published this manual designed to incorporate theories of death and rebirth based on the Tibetan Book of the Dead into rituals using psychedelics. This slim and very popular book offered readers advice on experiencing “ego death” and its subsequent rebirth and became a coveted publication for a burgeoning psychedelic underground eager for guidance on how to experience nonordinary states of consciousness.

• Masters, Robert E. L., and Jean Houston. The Varieties of Psychedelic Experience. New York: Dell, 1966.

  Appearing just as the backlash to psychedelics, and especially LSD, was starting to take hold in US society and drug policy, this book by husband-and-wife researchers Masters and Houston was notably popular. Titled in an homage to pioneering American psychologist William James, this book exemplifies the hopeful enthusiasm if not utopianism that characterized many early psychedelic advocates then as today.

• Osmond, Humphry. “A Review of the Clinical Effects of Psychotomimetic Agents.” Annals of the New York Academy of Science 66 (1957): 417–435.

  DOI: 10.1111/j.1749-6632.1957.tb40738.x

  In this landmark paper, Osmond makes the case for the usage of “psychedelic” to refer to substances that were until then discussed in widely varying ways. Coined in correspondence with Aldous Huxley, psychedelic (“mind manifesting”) first appears in print here, expressing Osmond’s hope that it might “help us explore and fathom our own nature.”

• Perrine, Daniel M. The Chemistry of Mind-Altering Drugs: History, Pharmacology, and Cultural Context. Washington, DC: American Chemical Company, 1996.

  This survey of mind-altering drugs by American chemist Daniel Perrine is notable for many reasons, not least its comprehensive chapter on psychedelics. His expertise in the science and technique of organic chemistry sets it apart from most other accounts of psychedelics, which tend to ignore the rich complexity of this component of their story.

• Rätsch, Christian. The Encyclopedia of Psychoactive Plants: Ethnopharmacology and Its Applications. Rochester, VT: Park Street Press, 2005.

  A book without equal in terms of scale and scope, this volume by German anthropologist Christian Rätsch provides an astonishingly vast survey of psychoactive plants. Translated from the original German, this book provides more than lip service to many hundreds of plants with psychoactive and psychedelic properties.

• Schultes, Richard E., and Albert Hofmann. Plants of the Gods. New York: McGraw-Hill, 1979.

  Two luminaries in their respective fields of ethnobotany and psychoactive chemistry, Schultes and Hofmann collaborated on this wonderfully written and illustrated classic. The book exhibits an appreciation for both the place of sacred and medicinal plants in Indigenous traditions as well as Western scientific interpretations and explorations. A revised and expanded 2nd edition by Christian Rätsch was translated from German and published in English in 2001.

• Schultes, R. E., and E. W. Smith. 1976. Hallucinogenic Plants. Golden Guide 35. New York: Golden Press

  In the popular Golden Guide series of pocketbooks aimed at young readers, ethnobotanist Richard Schultes and illustrator Elmer Smith produced a simple catalogue of hallucinogenic plants based on Schultes extensive fieldwork in the Amazon. Complete with chemical, botanical, and cultural illustrations, this informative guide served as a naturalist field guide to the hallucinogenic world of Amazonian plants and the Indigenous rituals that gave meaning to the accompanying experiences.

• Shulgin, Alexander, and Ann Shulgin. PIHKAL: A Chemical Love Story. Berkeley, CA: Transform Press, 1991.

  Phenethylamines I Have Known and Loved (PIHKAL) is a recipe book for chemists and psychonauts alike by one of the most infamous psychedelic couples. Chemist extraordinaire Alexander Shulgin and his wife, psychologist and psychedelic matriarch Ann Shulgin, walk readers through the wonders of psychedelic chemistry and experience, including one of their signature contributions—the reintroduction of MDMA. The Shulgins published another edition about tryptamines in 1997: TIHKAL: The Continuation.

• Stafford, Peter. Psychedelics Encyclopedia. Berkeley, CA: And/Or Press, 1977.

  An encyclopedic chronicling of psychedelic drugs, both above and below ground, along with the science and media headlines that propelled them into the 1960s zeitgeist. Complete with scientific references and descriptions of the effects of each substance, the Stafford Encyclopedia became a collectors’ item in the era of prohibition.

• Weil, Andrew, and Winifred Rosen. From Chocolate to Morphine: Everything You Need to Know about Mind-Altering Drugs. Boston: Houghton Mifflin, 1993.

  Andrew Weil occupies a unique place in American psychedelic history, having blown the whistle on unsavory aspects of Tim Leary’s Harvard psilocybin study, only later to be viewed as something of a counterculture figure himself. This broad, well-written survey, first published in 1983, was used as a textbook by eminent psychedelic chemist Alexander “Sasha” Shulgin in his seminal The Nature of Drugs pharmacology course taught in 1987.