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Hallucinogenic drug

Hallucinogenic drugs or hallucinogens are drugs that can alter sensory perceptions, elicit alternate states of consciousness, or cause hallucinations. This is a broad category that covers many disparate substances, the class of pharmacological agents which primarily change the subjective qualities of perception, thought or emotion.

Hallucinogens act as neurotransmitter mimics, often as agonists or antagonists at neurotransmitter receptors. The effects of hallucinogens are clearly different from stimulants like cocaine or amphetamines, although hallucinogens do often increase alertness or activity.

The broad term "hallucinogen" is often used as a synonym for the class of psychedelics (LSD, magic mushrooms, mescaline, or 2C-I), especially in the current scientific literature. Other classes include the empathogens or entactogens (MDMA), the deliriants (Datura, tropane alkaloids), or the dissociatives (DXM, PCP).


Etymology and alternative terms

A variety of different, imprecise terms have also been used to refer to drugs of this type. One of the first terms used in English to describe these substances was "Phantastica", coined in 1928 by Louis Lewin in his ground-breaking monograph of the same name. The term was applied to plants that "bring about evident cerebral excitation in the form of hallucinations, illusions and visions ... followed by unconsciousness or other symptoms of altered cerebral functioning." Lewin complained that the word "does not cover all that I should wish it to convey", and indeed with the advent of the discovery of LSD and the widespread scientific experimentation with it and similar drugs, numerous supposedly improved terms were constructed, including hallucinogen, psychedelic, psychotomimetic, psycholytic, schizophrenogenic, cataleptogenic, mysticomimetic and psychodysleptic.

Of all the terms created, "hallucinogen", meaning roughly "generating delusions and false notions" (particularly in the form of sensory distortions), probably enjoys the most widespread and accepted usage. "Psychedelic", meaning "mind manifesting" and emphasizing the introspective potential of the drugs, and "entheogen", meaning "becoming divine within", are also widely used, particularly among those with positive attitudes towards their usage. In some cases, authors who otherwise use these terms have felt themselves pressured to use "hallucinogen" or "psychotomimetic" (meaning "mimicking psychosis") in scientific publications. The terms "empathogen" and "entactogen" are also applied to certain drugs (notably those similar to MDMA) that are also sometimes classed as hallucinogens.

History of use

Hallucinogenic drugs are among the oldest drugs used by humankind, as hallucinogens naturally occur in mushrooms, cacti, and various other plants. Whether the use of hallucinogens is encouraged, unregulated, regulated, or prohibited, and whether hallucinogens are used for recreational, medicinal, or spiritual purposes, varies from culture to culture and nation to nation. In most nations of the world, the possession of many hallucinogens, even those that are common in nature, is a crime punished by fines, imprisonment or in many countries, death. For some religious purposes, however, there are exceptions. For instance, though possession of peyote cactus is illegal for most purposes in the United States, American Courts have upheld the Constitutional right of Native Americans to grow and consume peyote.

Traditional religious and shamanic use (entheogens)

In human culture hallucinogens have historically most commonly been used in the setting of religious or shamanic rituals. In this context they are more precisely referred to as entheogens, and are used to facilitate healing, divination, communication with the spirits, and coming of age ceremonies. Evidence exists for the use of entheogens in prehistoric times, as well as in numerous ancient cultures, including the Ancient Egyptian, Mycenaean, Ancient Greek, Vedic, Maya, Inca and Aztec cultures. The rise of the Abrahamic religions (Judaism, Christianity and Islam) caused a decline of entheogen use in their area. Witness the destruction of the Eleusinian Mysteries, or the Great Witch Hunt of the Early Modern Age , in which practitioners of entheogenic rites in Western Europe were accused of associating with the Devil. Nevertheless, some (mainly tribal) cultures have survived this (ongoing) assault and still practise entheogen use. In others, non-religious hallucinogen use, while not exactly encouraged, is tolerated and not seen as uncommon. Present-day, historical and mythological aspects of entheogens are discussed in the entry entheogen.

Early scientific investigations

Although natural hallucinogenic drugs have been known to mankind for millennia, it was not until the early 20th century that they received extensive attention from Western science. Earlier beginnings include scientific studies of nitrous oxide in the late 18th century, and initial studies of the constituents of the peyote cactus in the late 19th century. Starting in 1927 with Kurt Beringer 's Der Meskalinrausch (The Mescaline Intoxication), more intensive effort began to be focused on studies of psychoactive plants. Around the same time, Louis Lewin published his extensive survey of psychoactive plants, Phantastica (1928). Important developments in the years that followed included the re-discovery of Mexican magic mushrooms (in 1936 by Robert J. Weitlaner) and ololiuhqui (in 1939 by Richard Evans Schultes). Arguably the most important pre-World War II development was by Albert Hofmann's 1938 invention of the semi-synthetic drug LSD, which was later discovered to produce hallucinogenic effects, in 1943.

Hallucinogens after World War II

After World War II there was an explosion of interest in hallucinogenic drugs in psychiatry, owing mainly to the discovery of LSD. Interest in the drugs tended to focus on either the potential for psychotherapeutic applications of the drugs (see psychedelic psychotherapy), or on the use of hallucinogens to produce a "controlled psychosis", in order to understand psychotic disorders such as schizophrenia. Between the mid 1950s and the mid 1960s over 1000 scholarly articles were published on hallucinogen research. Hallucinogens were also researched in several countries for their potential as agents of chemical warfare. Most famously, several tragic incidents associated with the CIA's MK-ULTRA mind control research project have been the topic of media attention and lawsuits.

At the beginning of the 1950s, the existence of hallucinogenic drugs was virtually unknown among the general public of the West. However this soon changed as several influential figures were introduced to the hallucinogenic experience. Aldous Huxley's 1953 essay The Doors of Perception, describing his experiences with mescaline, and R. Gordon Wasson's 1957 Life magazine article (Seeking the Magic Mushroom) brought the topic into the public limelight. In the early 1960s countercultural icons such as Timothy Leary, Allen Ginsberg and Ken Kesey advocated the drugs for their psychedelic effects, and a large subculture of psychedelic drug users was spawned. Many people argue that psychedelic drugs played a major role in catalyzing the vast social changes initiated in the 1960s.

As a result of the growing popularity of LSD, and, some contend, establishment disdain for the hippies with whom it was heavily associated, LSD was banned in the United States in 1967.

Social status of hallucinogens

After the fading from public sight of many elements of the 1960s counterculture, hallucinogen use took a less visible but nevertheless persistent role in Western society 1970s and 1980s. In the 1990s and 2000s something of a revival of interest in the drugs has occurred. There are probably several important contributing factors to the resurgence. One is the rise of dance-based rave and trance culture, in which participants frequently employ drugs such as the empathogen MDMA, and to a lesser extent, other hallucinogenic drugs such as LSD, magic mushrooms and ketamine, as an aid to inducing ecstatic or trance states of consciousness. A second major contributing factor to the revival of interest in hallucinogenic drugs has been the advent of the Internet and World Wide Web. This has made information pertaining to drugs much more accessible to the general public, provided a platform for advocacy that was not previously available, and has enabled otherwise isolated interested parties to communicate and exchange information and experiences. Some well-known contemporary authors of topics relating to hallucinogens include Terence McKenna, Alexander Shulgin, Jonathan Ott and Rick Strassman.

Legal status

As of 2004, most hallucinogens are illegal in most Western countries. One notable exception to the current criminalization trend is in parts of Western Europe, especially in the Netherlands, where hallucinogenic mushrooms are considered to be so-called "soft drugs", along with cannabis. While the possession of soft drugs is technically illegal, the Dutch government has decided that using law enforcement to combat their use is largely a waste of resources. As a result, public "coffeeshops" in the Netherlands openly sell cannabis, and "smart shops" sell drugs like psilocybin mushrooms and ayahuasca for personal use (See Drug policy of the Netherlands).

Since the latter part of the twentieth century, this attitude has spread throughout Europe; many European countries no longer actively pursue anti-drug policies, and rarely enforce extant legal penalties for personal-use quantities of hallucinogenic drugs. This is especially true with mild hallucinogens such as cannabis, which is rapidly gaining acceptance in western Europe as a harmless and socially acceptable intoxicant, much as alcohol is considered throughout the West. Despite being scheduled as a controlled substance in the mid 1980s, ecstasy's popularity has been growing since that time in western Europe and in the United States.

Attitudes towards hallucinogens other than cannabis have been slower to change. Several attempts to change the law on the grounds of freedom of religion have been made. Some of these have been successful, for example the Native American Church in the United States, and the international Santo Daime . Some people argue that a religious setting should not be necessary for the legitimacy of hallucinogenic drug use, and for this reason also criticize the euphemistic use of the term "entheogen". Non-religious reasons for the use of hallucinogens including spiritual, introspective, psychotherapeutic, recreational and even hedonistic motives, each subject to some degree of social disapproval, have all been defended as the legitimate exercising of civil liberties, including freedom of thought.


Hallucinogens can be classified by quality of action, mechanisms of action, or by chemical structure. These classifications often correlate to some extent. The classification system below attempts to blend these three approaches in order to create a balanced and simple overview that is as clear and easy to grasp as possible.

Almost all hallucinogens contain nitrogen and are classified as alkaloids. THC and Salvinorin A are exceptions. Many hallucinogens often have chemical structures similar to those of human neurotransmitters, such as serotonin, and temporarily interfere with the action of neurotransmitters and/or receptor sites.

A classical classification is that of Lewin (Phantastica, 1928):
Class I Phantastica roughly correspond to the psychedelics, which is a more modern term usually used as synonym to "hallucinogen" by people with positive attitudes towards them. Here the term is used a bit differently to discriminate one particular class of hallucinogens which it seems to describe best. They typically have no sedative effects (sometimes the opposite) and there is usually a clearcut memory to their effects.

Class II Phantastica correspond to the other classes in this scheme. They tend to sedate in addition to their hallucinogenic properties and there often is an impaired memory trace after the effects wear off.

Pharmacological classes of hallucinogens, and their general subjective effects

Entries marked with a # are naturally occurring.

Psychedelics (serotonin 5-HT2A receptor agonists)

Commentary: The tryptamines, LSD, and phenethylamines cause more or less identical effects despite their different chemical structure. At lower doses, these include sensory distortions such as the warping of surfaces, shape suggestibility, and color variations. Users often report intense colors that they have not previously experienced, and repetitive geometric shapes are common. Higher doses often cause intense and fundamental distortions of sensory perception such as synaesthesia or the experience of additional spatial, temporal, or time dimensions. Some compounds, such as 2C-B, have extremely tight "dose curves," meaning the difference between a non-event and an overwhelming disconnection from reality can be very slight.

Empathogens or Entactogens (serotonin releasers)


Commentary: These three groups of dissociatives have slightly different effects but also share similarities separating them from other classes of hallucinogens. They are markedly different from psychedelics such as LSD, where alert and fully conscious users experience cognitive distortion while simultaneously interacting with the "real world". Hallucinations from these dissociatives are generally only experienced in dark rooms or with eyes closed, unless at very high doses above what is normally consumed recreationally. Nitrous oxide has very different effects however, and even at low doses includes auditory distortions. Unlike with many other psychedelic chemicals, salvia users are generally not ambulatory and the experience is frequently dissociative. Often a very brief trance is entered, where the user experiences an intense and very realistic dream state. On the other hand, the effect of salvia on emotion has been reported to be less marked than that of true psychedelics.

Deliriants (anticholinergics)

Commentary: Anticholinergics are sometimes called "true hallucinogens". These substances are the most likely to produce what is traditionally thought of as a hallucination, namely seeing and hearing fully realistic objects, persons, and sounds that are not truly there, as opposed to color changes or other distortions in vision. However, they have a great number of strong, unpleasant and possibly life-threatening physiological effects as well, and thus are used very rarely for their hallucinogenic properties.


Cannabinoids (CB-1 cannabinoid receptor agonists)


Commentary: Although muscimol does not usually cause normal hallucinations, it has a tendency to put the user to sleep, during which the user is able to have very vivid dreams with good dream recall.

Other (hallucinogenic activity questioned)

Hallucinogenic plants, fungi, and animals

Among the most well-known hallucinogenic plants and fungi are:

Among the most well-known animals that secrete hallucinogens are:

See also

External links


  • Science & Consciousness Review, The Neurochemistry of Psychedelic Experience:

Last updated: 10-15-2005 13:20:17
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