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Definition: hallucinogen from Hawley's Condensed Chemical Dictionary

Any of a number of drugs acting on the central nervous system in such a way as to cause mental disturbance, imaginary experiences, coma, and even death. Many of these are narcotics and/or alkaloids; some are derived from plants and others are made synthetically. They differ in degree of addiction and hallucinatory effect. Their sale and possession (other than by physicians) is illegal in the U.S. The most common hallucinogens are cannabis (marijuana, hashish), lysergic acid (LSD), amphetamine, and numerous morphine derivatives.

Summary Article: Hallucinogens from Encyclopedia of Drug Policy: "The War on Drugs" Past, Present, and Future

Hallucinogens are substances known to cause changes in awareness, thought processes, and feelings, thereby altering perception of reality. For centuries, hallucinogens have been used for medical purposes, recreation, and religious experiences. Scientists began experimenting with various hallucinogens to see what effects they have on the body. Psychiatrists and other mental health professionals have also used hallucinogens as part of the treatment process for certain mental illnesses.

Hallucinogens, sometimes referred to as psychedelic drugs, became very popular in Western culture staring in the mid-20th century. Hallucinogens played an especially significant role during the counterculture movement of the 1960s, as these substances were widely viewed as initiating a new social movement. Many controversies regarding hallucinogens exist, especially with regard to their place in society. Organizations have been formed in order to pursue the legalization of some hallucinogens as a way to heal the body.

Hallucinogens are divided into three categories: psychedelics, dissociatives, and deliriants. Psychedelics are drugs that induce stages of altered perception and thought with heightened awareness of sensory input. The drugs cause persons ingesting them to have little control over what is actually being experienced. Popular psychedelics include both synthetic forms such as lysergic acid diethylamide (LSD) and herbal and fungal forms, such as dimethyltryptamine (DMT) and psilocybe mushrooms (“magic mushrooms”). Some consider other drugs such as marijuana psychedelics, because when used in large quantities they can also produce similar effects.

Dissociatives work to reduce or block signals to the conscious mind from other parts of the brain. This occurs because some dissociatives inhibit perceptions of the physical senses while others dissociate physical senses from sensory data. Either reaction results in sensory signals being blocked from the brain, causing the brain to undergo sensory deprivation. Sensory deprivation may result in hallucinations and a dreamlike state of mind. Widely used dissociatives are phencyclidine (PCP or “angel dust”); ketamine, a common anesthetic; and dextromethorphan, an active ingredient used in cough syrups. Most dissociatives have depressant effects that slow breathing and heart rates to levels that could cause death if used in high dosages.

Deliriants are a subgroup of dissociatives, and are sometimes referred to as “true hallucinogens” because they indeed cause hallucinations. Individuals using deliriants sometimes are observed having conversations with others who are not there, or becoming upset at another who is believed to be mimicking the deliriant-taker's actions. Deliriants have been known to cause lucid dreaming, or the act of one consciously being aware of one's dreams. Side effects of deliriants include hallucinations, confusion, rage, feelings of isolation, and sleepwalking. When taken at suggested doses, deliriants have many beneficial uses. Deliriants are found both naturally, such as in plants including nightshades, mandrakes, and henbane, as well as in many pharmaceutical drugs such as antihistamines like Benadryl.

While labeled as hallucinogens, most of these drugs do not cause hallucinations. Hallucinations are perceptions that occur in the absence of external stimuli, and are often vivid, substantial, and located in external objective space. Users of psychedelic drugs experience a change in their regular perception but are very aware of the change that is occurring. Dissociatives cause sensory deprivation, which often leads to euphoria, but less often leads to hallucinations. True hallucinations most often occur when a person is under the influence of deliriants.

Cultural Practices

Hallucinogens are some of the oldest drugs used, with a global appeal that crosses cultures and time. Hallucinogens have been used for many medicinal, religious, and recreational uses, both formally and informally. Hallucinogens have been used as a form of ritual healing, for divination of the supernatural, and initiation into various groups or societies. When hallucinogens are used as part of religious ceremonies, the practice is called entheogenic. Entheogens create “gods within” through the use of hallucinogens that assist with healing, divination, communication with spirits, and ritual ceremonies. Many cultures have used entheogens, including the ancient Egyptians, the Mycenaeans, the ancient Greeks, and the Aztecs. These cultures, and many others, used hallucinogens for ritual practices. The use of entheogenics declined in areas where Judaism, Christianity, and Islam were popular due to these groups' disapproval of the practice. Hallucinogens were thus most popular as a part of cultural practices, and indeed remain not uncommon, in less developed areas of the world.

The Aztecs viewed psilocybin mushrooms as scared, and images of the mushrooms were featured in their art and architecture. After the Spanish conquest, psilocybin mushrooms were viewed with suspicion and suppressed, with missionaries suggesting the Eucharist as a worthy substitute. Use of psilocybin mushrooms has continued in remote areas, however, to the present. Lophophora williamsii (peyote) was used by the indigenous peoples of what is today northern Mexico and the southwestern United States. Tribes traditionally using peyote included the Huichol, the Tonkawa, the Mescalero, the Lipan Apache, the Comanche, and the Kiowa. Beginning in the 19th century, the Native American Church introduced the use of peyote to members of tribes that had not traditionally used it, such as the Navajo. Other groups that have sought to reintroduce the use of hallucinogens include União do Vegetal and Santo Daime.

Scientific Research

Hallucinogens have been the subject of medical research for several hundred years, although they did not receive extensive attention from the scientific community until the 20th century. Early studies examining nitrous oxide were conducted in the 18th century, exploratory research was done with peyote in the 19th century, and psilocybin mushrooms were examined during the early 20th century. After World War II, however, hallucinogenic drugs were viewed as a way to better understand psychotic disorders such as schizophrenia, and their use in research experiments increased. Specifically, psychedelics were investigated as a possible way to control psychosis and other disorders. Between 1945 and 1950 over 100 articles on LSD appeared in medical journals, a number which had increased to over 1,000 by 1960.

The focus during the 1950s and 1960s was to investigate whether hallucinogens could be used in conjunction with psychotherapy as a means to treat patients suffering from disorders that had long bedeviled the medical community. LSD, for example, was used to treat individuals who suffered from alcoholism, as a way to ameliorate the pain and suffering of individuals with cancer, and as a treatment for children with autism.

Hallucinogens proved problematic as a form of medical treatment because they were found to exacerbate certain conditions. Psychedelics, for example, have been found to aggravate depression, obsessive-compulsive disorder, and schizophrenia. Most hallucinogens have long-term physical toxicity and remain in the body for extended periods of time. Hallucinogens such as amphetamine are known to cause cell damage, and are strongly correlated with conditions such as schizophrenia and Alzheimer's and Parkinson's disease. Because of these problems, interest in hallucinogens waned after the 1960s. Research continues, however, into the potential use of hallucinogens for treatment to assist individuals with alcoholism and mental disorders. Some limited use of hallucinogens continues as part of certain psychotherapeutic treatments. Hallucinogens have also been shown to help some patients with post-traumatic stress disorder, cluster headaches, and depression.

Cultural Movement

Hallucinogens, and especially the psychedelic LSD, became very popular during the 1960s and early 1970s. In many ways defining the rebellious spirit and experimental attitude of many involved in the counterculture movement, use of hallucinogens became more widespread and common than ever before. The desire of many youths during the 1960s for alternative forms of self-expression, coupled with antiwar sentiments and economic prosperity, served as the development of a counterculture movement in which experimentation with mind-altering drugs was seen as a way to explore concepts of self-actualization. Many prominent advocates for the use of hallucinogens came from the artistic and academic community, including Jerry Garcia, Aldous Huxley, Ken Kesey, Timothy Leary, and John Lennon. These individuals' use of hallucinogens, and their willingness to share their experiences, greatly increased the substances' popularity with others. Although hallucinogens were much less common than other substances, such as marijuana, cocaine, or even heroin, their use instilled fear in government leaders, educators, and parents to an extent disproportionate with their use. After the early 1970s, the use of hallucinogens declined until the 1990s, when a new generation of youth began using them, especially LSD and 3,4-methylenedioxymethamphetamine

(MDMA or ecstasy). MDMA, which was not classified as a Schedule I substance in the United States until 1985, was especially popular in dance clubs and as part of the rave culture. When used in conjunction with dance music and lights, hallucinogens became much more popular, with MDMA trailing only marijuana, cocaine, and heroin among illegal substances by the late 1990s. Indeed, MDMA trails only marijuana as the most likely first-time illicit drug used by young people.


Although illicit drug use was rare overall before 1960, this was especially true for hallucinogens. While marijuana, cocaine, barbiturates, amphetamines, opium, heroin, and morphine all had groups who used them, hallucinogens were quite rare until after World War II, so much so that their use tended to escape notice of federal agencies such as the Bureau of Narcotics and the Bureau of Drug Abuse Control (predecessors to the Drug Enforcement Administration). LSD, for example, was legally used by physicians as an experimental psychiatric drug until 1966. With the rising popularity of hallucinogens caused by the counterculture, however, these substances became more closely scrutinized by federal, state, and local authorities.

In 1961 the United States became a signatory to the Single Convention on Narcotic Drugs (Single Convention), an international treaty organized under the auspices of the United Nations. While previous international treaties had dealt with opium, coca, and their derivatives such as cocaine, morphine, and heroin, the Single Convention sought to regulate all drug production, trade, and use. The Single Convention contained four schedules, or categories, of drugs. Schedule I contained the most restrictive list of drugs while Schedule IV controlled the least-restricted substances. The Single Convention did not control psychoactive drugs, such as hallucinogens. As a non-self-executing agreement, however, it set in motion a variety of U.S. domestic policy changes that led to much stricter controls over hallucinogens. The U.S. Congress passed the Controlled Substances Act (CSA) as Title II of the Comprehensive Drug Abuse Prevention and Control Act of 1970. The CSA created five Schedules classifying various narcotics and pharmaceuticals, with Schedule I containing the most potentially harmful substances and Schedule V is comprised of the more benign drugs. When the schedules were created by the DEA and the FDA, hallucinogens were placed in Schedule I even though this predated the 1971 signing of the Convention on Psychotropic Substances, an international treaty similar to the Single Convention and designed to cover amphetamines, barbiturates, and hallucinogens.

These foil wrappers were used for doses of phencyclidine (PCP), a dissociative drug also known as “angel dust.”

Drug enforcement experiences with hallucinogens have been slightly different than that with other substances, such as marijuana, cocaine, and heroin. First, the incidence of hallucinogen use is much less than that of the other substances. Demographic research suggests that typical hallucinogen users are Caucasian, middle-class, male, and between 16 and 23 years of age. Unlike drugs with a higher incidence of abuse, LSD is used infrequently (i.e., not daily) and use tapers off after two to four years, usually after a negative experience with the substance (i.e., a “bad trip”). Second, unlike other substances that are imported, distributed, and sold by profit-seeking groups, hallucinogen manufacturers often are users who do not make a substantial profit. Instead, the manufacturers and sellers of hallucinogens are much more likely to consider their work in the “public service.” This makes their detection and apprehension more difficult, as it deprives law enforcement agents a money trail to detect and follow. Finally, certain American Indian tribes have legally protected rights to use hallucinogens such as peyote for traditional religious purposes. Although non-Indian use of peyote is generally not permitted, complications from these laws sometimes hinder prosecutions.

Current Trends

The dissociatives dextromethorphan, diphenhydramine, and dimenhydrinate are legal in most developed nations. As of 2010, most other hallucinogens remained illegal. Marijuana, which is considered by some a hallucinogen, is the only drug that has been decriminalized. Use of certain hallucinogens was allowed, although this has changed—the Netherlands permitted the use of hallucinogenic mushrooms until several unfortunate incidents involving tourists caused the Dutch government to ban their use. The Netherlands has not made drugs such as marijuana legal, but the Dutch government feels that enforcing its ban is a waste of resources. As a result, many drugs are available for purchase in the Netherlands by tourists. While the primary drug available for purchase remains cannabis, other substances such as ayahuasca and salvia divinorum can be purchased.

There has also been a growing movement in the United States to decriminalize small amounts of marijuana intended for personal or medical use. Eleven states have decriminalized the personal use of marijuana, as have multiple municipalities. Although state and local attempts to decriminalize cannabis possession have been popular, these statutes and ordinances do not protect users from federal laws that determine cannabis is illegal. Additionally, historical discomfort at the use of hallucinogens makes it much less likely that substances other than marijuana will receive similar treatment.

Some American Indian tribes use hallucinogens as part of their traditional religious ceremonies and rituals. Groups such as the Native American Church, União de Vegetal, and Santo Daime have had their right to use hallucinogens upheld because this usage was associated with entheogenic practices. Other, non-tribal Caucasians have attempted to use hallucinogens based upon the argument of religious freedom without success. As part of its responsibilities, the Office of National Drug Control Policy (ONDCP) conducts the National Survey on Drug Use and Health (National Survey). Results reported in the National Survey suggest that use of hallucinogens has been declining among U.S. youth. The National Survey notes that while in 1995, slightly over 3,000 individuals sought treatment for hallucinogen abuse, that number had declined to approximately 2,000 by 2005. Teenage drug use of hallucinogens also declined between 2001 and 2008, as reported by the National Survey. For example, youth drug use of MDMA had declined from 2.4 percent of the population in 2001 to 1.2 percent in 2008, while LSD usage declined from 1.5 percent to 0.7 percent for the same period.

Hallucinogens continue to inspire great passions among those who favor or disapprove their use. While incidence of hallucinogen use remains small, at least in relative terms to other substances, it remains a popular topic with politicians, the mass media, anti-drug activists, and civil libertarians. Hallucinogens have demonstrated a level of popularity with certain groups, a demand that has returned on several occasions. As attitudes toward other controlled substances evolve, public policy regarding hallucinogens may also shift.

See Also

Ecstasy, Food and Drug Administration, Gonzales v. O Centro Espirita Beneficente União do Vegetal (2006), LSD, Office of National Drug Control Policy, Religious Freedom and Drug Laws, Single Convention on Narcotic Drugs, 1961, “War on Drugs”

Further Readings
  • Engberg, J. and Morral, A. R. “Reducing Substance Abuse Improves Adolescents' School Attendance.” Addiction, v.101/12: 2006.
  • Jacobs, A. “Acid Redux: Revisiting LSD Use in Therapy.” Contemporary Justice Review, v.11/4: 2008.
  • Laing, R. R., ed. Hallucinogens: A Forensic Drug Handbook. London: Academic Press, 2003.
  • Schroth, Stephen T.
    Helfer, Jason A.
    Mahone, Christian D.
    Knox College
    Copyright © 2011 by SAGE Publications, Inc.

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