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Hallucinogenic compounds in the form

of, or extracted from, plants and mushrooms have been used for centuries,

mostly in religious rituals. Almost all 

hallucinogens contain nitrogen and are

classified as alkaloids. Many hallucinogens have chemical structures similar to

those of neurotransmitters (e.g., acetylcholine-, serotonin-, or catecholaminelike) and temporarily interfere with their

action or bind their receptor sites, but the

exact mechanisms by which these substances exert their hallucinogenic effects

remain unclear. This InfoFacts will discuss

four common types of hallucinogens:

• LSD (d-lysergic acid diethylamide) 

is one of the most potent moodchanging chemicals. It was discovered in 1938 and is manufactured

from lysergic acid, which is found in

ergot, a fungus that grows on rye

and other grains. 

• Peyote is a small, spineless cactus in

which the principal active ingredient

is mescaline. This plant has been

used by natives in northern Mexico

and the southwestern United States

as a part of their religious rites.

Mescaline can also be produced

through chemical synthesis. 

• Psilocybin (4-phosphoryloxy-N,Ndimethyltryptamine) is obtained from

certain types of “magic” mushrooms

that are indigenous to tropical and

subtropical regions of South

America, Mexico, and the United

States. These mushrooms typically

contain less than 0.5 percent psilocybin plus trace amounts of psilocin,

another hallucinogenic substance. 

• PCP (phencyclidine) was developed

in the 1950s as an intravenous anesthetic, but this use has been discontinued due to serious adverse effects.

How are Hallucinogens

Abused? 

The very same characteristics that led 

to the incorporation of hallucinogens

into ritualistic or spiritual traditions have

also led to their propagation as drugs 

of abuse. Importantly, and unlike most

other drugs, the effects of hallucinogens

are highly variable and characteristically

unreliable, producing different effects 

in different people or at different times.

This is mainly due to the significant variations in amount and composition of

active compounds, particularly in the

hallucinogens derived from plants and

Hallucinogens: LSD, Peyote,

Psilocybin, and PCP
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mushrooms. Because of their unpredictable nature, the use of hallucinogens

can be particularly dangerous. 

• LSD is sold in tablets, capsules, and,

occasionally, liquid form; thus, it is

usually taken orally. LSD is often

added to absorbent paper, which is

then divided into decorated pieces,

each equivalent to one dose. The

experiences, often referred to as

“trips,” are long; typically, they

begin to clear after about 12 hours.

• Peyote. The top of the peyote cactus—also referred to as the crown—

consists of disc-shaped buttons that

are cut from the roots and dried.

These buttons are generally chewed

or soaked in water to produce an

intoxicating liquid. The hallucinogenic

dose of mescaline is about 0.3 to 0.5

grams, and its effects last about 12

hours. Because the extract is so bitter,

some prefer to prepare a tea by boiling the cacti for several hours.

• Psilocybin. Mushrooms containing

psilocybin are available fresh or

dried and are typically taken orally.

The active psilocin (4-hydroxy-N,Ndimethyltryptamine) and psilocybin

(4-phosphoryloxy-N,N-dimethyltryptamine) cannot be inactivated by cooking or freezing preparations. Thus,

they may also be brewed as a tea or

added to other foods to mask their

bitter flavor. The effects of psilocybin,

which appear within 20 minutes of

ingestion, last approximately 6 hours.

• PCP is a white crystalline powder

that is readily soluble in water or

alcohol. It has a distinctive bitter

chemical taste. PCP can be mixed

easily with dyes and turns up on the

illicit drug market in a variety of

tablets, capsules, and colored powders. It is normally snorted, smoked,

or ingested. For smoking, PCP is

often applied to a leafy material

such as mint, parsley, oregano, or

marijuana. Depending upon how

much and by what route PCP is

taken, its effects can last approximately 4–6 hours.

How do Hallucinogens Affect

the Brain?

LSD, peyote, psilocybin, and PCP are

drugs that cause hallucinations, which

are profound distortions in a person’s

perception of reality. Under the influence

of hallucinogens, people see images,

hear sounds, and feel sensations that

seem real but do not exist. Some hallucinogens also produce rapid, intense

emotional swings. LSD, peyote, and

psilocybin cause their effects by initially

disrupting the interaction of nerve cells

and the neurotransmitter serotonin.1

Distributed throughout the brain and

spinal cord, the serotonin system is

involved in the control of behavioral,

perceptual, and regulatory systems,

including mood, hunger, body temperature, sexual behavior, muscle control,

and sensory perception. PCP, on the

other hand, acts mainly through a type
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of glutamate receptor in the brain, important for the perception of pain, responses

to the environment, and memory.

There have been no properly controlled

research studies on the specific effects of

these drugs on the human brain, but

smaller studies and several case reports

have been published documenting some

of the effects associated with the use of

hallucinogens:

• LSD. Sensations and feelings change

much more dramatically than the

physical signs. The user may feel several different emotions at once or

swing rapidly from one emotion to

another. If taken in large enough

doses, the drug produces delusions

and visual hallucinations. The user’s

sense of time and self is altered.

Experiences may seem to “cross

over” different senses, giving the user

the feeling of hearing colors and seeing sounds. These changes can be

frightening and can cause panic.

Some LSD users experience severe,

terrifying thoughts and feelings of

despair, fear of losing control, or

fear of insanity and death while

using LSD. 

LSD users can also experience flashbacks, or recurrences of certain

aspects of the drug experience.

Flashbacks occur suddenly, often

without warning, and may occur

within a few days or more than a

year after LSD use. In some individuals, the flashbacks can persist and

cause significant distress or impairment in social or occupational functioning, a condition known as hallucinogen-induced persisting perceptual disorder (HPPD). 

Most users of LSD voluntarily

decrease or stop its use over time.

LSD is not considered an addictive

drug since it does not produce compulsive drug-seeking behavior.

However, LSD does produce tolerance, so some users who take the

drug repeatedly must take progressively higher doses to achieve the

state of intoxication that they had

previously achieved. This is an

extremely dangerous practice, given

the unpredictability of the drug. In

addition, cross-tolerance between

LSD and other hallucinogens has

been reported.

• Peyote. The long-term residual psychological and cognitive effects of

mescaline, peyote’s principal active

ingredient, remain poorly understood. A recent study found no evidence of psychological or cognitive

deficits among Native Americans

that use peyote regularly in a religious setting.2 It should be mentioned, however, that these findings

may not generalize to those who

repeatedly abuse the drug for recreational purposes. Peyote abusers

may also experience flashbacks.

• Psilocybin. The active compounds in

“magic” mushrooms have LSD-like

properties and produce alterations of
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autonomic function, motor reflexes,

behavior, and perception.3 The psychological consequences of psilocybin use include hallucinations, an

altered perception of time, and an

inability to discern fantasy from reality. Panic reactions and psychosis

also may occur, particularly if a user

ingests a large dose. Long-term

effects such as flashbacks, risk of

psychiatric illness, impaired memory,

and tolerance have all been

described in case reports.

• PCP. The use of PCP as an approved

anesthetic in humans was discontinued in 1965 because patients often

became agitated, delusional, and

irrational while recovering from its

anesthetic effects. PCP is a “dissociative drug,” meaning that it distorts

perceptions of sight and sound and

produces feelings of detachment (dissociation) from the environment and

self. First introduced as a street drug

in the 1960s, PCP quickly gained a

reputation as a drug that could

cause bad reactions and was not

worth the risk. However, some

abusers are attracted by feelings of

strength, power, and invulnerability

as well as a numbing effect on the

mind that PCP can induce. Among

the adverse psychological effects

reported are:

o Symptoms that mimic schizophrenia, such as delusions, hallucinations, paranoia, disordered thinking, and a sensation of distance

from one’s environment.

o Mood disturbances: For example,

approximately 50 percent of individuals presenting for druginduced problems in an emergency room setting and meeting

criteria for PCP use in the past 48

hours reported significant elevations in anxiety symptoms.4

o People who abuse PCP for long

periods of time report memory

loss, difficulties with speech and

thinking, depression, and weight

loss. These symptoms can persist

up to a year after stopping PCP

abuse. 

o Addiction: PCP is addictive—its

repeated abuse can lead to craving and compulsive PCP-seeking

behavior, despite severe adverse

consequences.

What Other Adverse Effects

do Hallucinogens Have on

Health?

Unpleasant adverse effects as a result of

the use of hallucinogens are not uncommon—one of the reasons is that there

are often a large number of psychoactive ingredients in any single source of

hallucinogen.3

• LSD. The effects of LSD depend largely on the amount taken. LSD causes

dilated pupils; can raise body temperature and increase heart rate and

blood pressure; and can cause profuse sweating, loss of appetite, sleeplessness, dry mouth, and tremors.
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• Peyote. Its effects can be similar to

LSD’s, including increased body temperature and heart rate, uncoordinated movements (ataxia), profound

sweating, and flushing. The active

ingredient mescaline has also been

associated, in at least one report, to

fetal abnormalities.5

• Psilocybin. It can produce muscle

relaxation or weakness, ataxia,

excessive pupil dilation, nausea,

vomiting, and drowsiness. Individuals

who abuse psilocybin mushrooms

also risk poisoning if one of the

many existing varieties of poisonous

mushrooms is incorrectly identified as

a psilocybin mushroom.

• PCP. At low to moderate doses,

physiological effects of PCP include

a slight increase in breathing rate

and a pronounced rise in blood pressure and pulse rate. Breathing

becomes shallow; flushing and profuse sweating, generalized numbness

of the extremities, and loss of muscular coordination may occur. 

At high doses, blood pressure, pulse

rate, and respiration drop. This may

be accompanied by nausea, vomiting, blurred vision, flicking up and

down of the eyes, drooling, loss of

balance, and dizziness. PCP abusers

are often brought to emergency

rooms because of overdose or

because of the drug’s severe untoward psychological effects. While

intoxicated, PCP abusers may

become violent or suicidal and are

therefore dangerous to themselves

and others. High doses of PCP can

also cause seizures, coma, and

death (though death more often

results from accidental injury or suicide during PCP intoxication).

Because PCP can also have sedative

effects, interactions with other central

nervous system depressants, such as

alcohol and benzodiazepines, can

also lead to coma.

What Treatment Options

Exist?

Treatment for alkaloid hallucinogen (such

as psilocybin) intoxication—which is

mostly symptomatic—is often sought as a

result of bad “trips,” during which a

patient may, for example, hurt him- or

herself.6 Treatment is usually supportive:

provision of a quiet room with little sensory stimulation. Occasionally, benzodiazepines are used to control extreme

agitation or seizures. 

There is very little published data on

treatment outcomes for PCP intoxication.

Doctors should consider that acute

adverse reactions may be the result of

drug synergy with alcohol.7 Current

research efforts to manage a life-threatening PCP overdose are focused on a

passive immunization approach through

the development of anti-PCP antibodies.8

There are no specific treatments for PCP

abuse and addiction, but inpatient

and/or behavioral treatments can be
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helpful for patients with a variety of

addictions, including that to PCP. 

How Widespread is the

Abuse of Hallucinogens?

According to the 2006 National Survey

on Drug Use and Health (NSDUH),†

there were 1.1 million persons aged 12

or older in 2006 who reported they had

used hallucinogens for the first time within the past 12 months. 

LSD

Monitoring the Future Survey††

There were no changes in LSD use from

2006 to 2007 for any prevalence periods among the 8th-, 10th-, and 12thgraders surveyed. Perceived risk of harm

from taking LSD regularly, however, significantly decreased among 10thgraders, from 60.7 percent in 2006 to

56.8 percent in 2007. Disapproval of

using LSD once or twice also significantly decreased among 10th-graders (from

71.2 percent in 2006 to 67.7 percent 

in 2007), as did disapproval of taking

LSD regularly (dropping from 74.9 percent in 2006 to 71.5 percent in 2007).

Such changes in attitude could signal a

subsequent increase in use, an outcome

that would be of great concern after 

the large decreases seen since the 

mid-1990s, when LSD use peaked

among youth.

National Survey on Drug Use and

Health†

In 2006, more than 23 million persons

aged 12 or older reported they had

used LSD in their lifetime (9.5 percent);

however, fewer than 700,000 had used

the drug in the past year. There was no

significant change between 2005 and

2006 in the number of past-year initiates

of LSD. 

Peyote and Psilocybin

It is difficult to gauge the extent of use of

these hallucinogens because most data

sources that quantify drug use exclude

these drugs. The Monitoring the Future

survey†† reported in 2007 that 7.7 percent of high school seniors had used hallucinogens other than LSD—a group that

includes peyote, psilocybin, and others—

at least once in their lifetime. Past-year

use was reported to be 4.8 percent.

PCP

Monitoring the Future Survey††

In 2007, 2.1 percent of high school 

LSD Use by Students

2007 Monitoring the Future Survey

8th Grade 10th Grade 12th Grade

Lifetime††† 1.6% 3.0% 3.4%

Past Year 1.1 1.9 2.1

Past Month 0.5 0.7 0.6
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seniors reported lifetime††† use of PCP;

past-year use was reported by 0.9 percent of seniors; and past-month use was

reported by 0.5 percent. Data on PCP

use by 8th- and 10th-graders are not

available.

National Survey on Drug Use 

and Health†

In 2006, 6.6 million persons aged 12 or

older reported that they had used PCP in

their lifetime (2.7 percent), although only

187,000 persons in the same age group

reported use in the past year—this represents a slight increase over 2005. 

National Institutes of Health – U.S. Department of Health and Human Services

This material may be used or reproduced without permission from NIDA. Citation of the source is appreciated.

† NSDUH (formerly known as the National Household Survey on Drug Abuse) is an annual survey of Americans age 12

and older conducted by the Substance Abuse and Mental Health Services Administration, Department of Health and

Human Services. Copies of the latest survey are available at www.samhsa.gov and from NIDA at 877-643-2644.

†† These data are from the 2007 Monitoring the Future survey, funded by the National Institute on Drug Abuse,

National Institutes of Health, Department of Health and Human Services, and conducted annually by the University of

Michigan’s Institute for Social Research. The survey has tracked 12th-graders’ illicit drug use and related attitudes since

1975; in 1991, 8th- and 10th-graders were added to the study. The latest data are online at www.drugabuse.gov.

††† “Lifetime” refers to use at least once during a respondent’s lifetime. “Past year” refers to use at least once during

the year preceding an individual’s response to the survey. “Past month” refers to use at least once during the 30 days

preceding an individual’s response to the survey.

References

1 Fantegrossi WE, Murnane KS, Reissig CJ. The behavioral pharmacology of hallucinogens. Biochem Pharmacol

75(1):17-33, 2008.

2 Halpern JH, Sherwood AR, Hudson JI, Yurgelun-Todd D, Pope HG Jr. Psychological and cognitive effects of long-term

peyote use among Native Americans. Biol Psychiatry 58(8):624–631, 2005.

3 Cunningham N. Hallucinogenic plants of abuse. Emerg Med Australas 20(2):167–174, 2008.

4 Yago, KB, Pitts, FN, Burgoyne, RW, Aniline, O, Yago, LS, Pitts AF. The urban epidemic of phencyclidine (PCP) use:

Clinical and laboratory evidence from a public psychiatric hospital emergency service. J Clin Psychiatry 42:193–196,

1981. 

5 Gilmore HT. Peyote use during pregnancy. S D J Med 54(1):27–29, 2001.

6 Attema-de Jonge ME, Portier CB, Franssen EJ. Automutilation after consumption of hallucinogenic mushrooms. 

Ned Tijdschr Geneeskd 151(52):2869–2872, 2007.

7 Schwartz RH, Smith DE. Clin Pediatr (Phila) 27(2):70–73, 1988.

8 Kosten T, Owens SM. Immunotherapy for the treatment of drug abuse. Pharmacol Ther 108(1):76–85, 2005.