May 2006 Page 1 of 3

LSD (lysergic acid diethylamide) is one

of the major drugs making up the hallucinogen class of drugs. Hallucinogens

cause hallucinations—profound distortions in a person’s perception of reality.

Hallucinogens cause their effects by 

disrupting the interaction of nerve cells

and the neurotransmitter serotonin.

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.

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. One of

the most potent mood-changing chemicals, LSD, was discovered in 1938 and

is manufactured from lysergic acid,

which is found in ergot, a fungus that

grows on rye and other grains.

Health Hazards ———

The effects of LSD are unpredictable.

They depend on the amount taken; the

user’s personality, mood, and expectations; and the surroundings in which the

drug is used. Usually, the user feels the

first effects of the drug 30 to 90 minutes

after taking it. The physical effects include

dilated pupils, higher body temperature,

increased heart rate and blood pressure,

sweating, loss of appetite, sleeplessness,

dry mouth, and tremors.

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 a

large enough dose, the drug produces

delusions and visual hallucinations. The

user’s sense of time and self changes.

Sensations may seem to “cross over,”

giving the user the feeling of hearing

colors and seeing sounds. These

changes can be frightening and can

cause panic.

Users refer to their experience with LSD

as a “trip” and to acute adverse reactions as a “bad trip.” These experiences

are long; typically they begin to clear

after about 12 hours.

Some LSD users experience severe, terrifying thoughts and feelings, fear of losing control, fear of insanity and death,

and despair while using LSD. Some fatal

accidents have occurred during states of

LSD intoxication.

LSD
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Many LSD users experience flashbacks,

recurrence of certain aspects of a 

person’s experience, without the user

having taken the drug again. A flashback occurs suddenly, often without

warning, and may occur within a few

days or more than a year after LSD use.

Flashbacks usually occur in people who

use hallucinogens chronically or have an

underlying personality problem; however,

otherwise healthy people who use LSD

occasionally may also have flashbacks.

Bad trips and flashbacks are only part

of the risks of LSD use. LSD users may

manifest relatively long-lasting psychoses, such as schizophrenia or severe

depression. It is difficult to determine the

extent and mechanism of the LSD

involvement in these illnesses.

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, as do cocaine, amphetamine,

heroin, alcohol, and nicotine. However,

like many of the addictive drugs, LSD

produces 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.

Extent of Use ———

Monitoring the Future (MTF)

Survey* 

Lifetime** use dropped significantly

among 12th-graders from 2004 to

2005, while annual and 30-day use

remained stable. (Also see the InfoFacts

on High School and Youth Trends.)

Perceived availability of the drug fell

among 12th-graders for this same period.

National Survey on Drug Use and

Health (NSDUH)***

NSDUH data show decreases in annual

use of LSD from 2002 to 2004. In

2004, 9.7 percent of Americans aged

12 and older reported using LSD at least

once in their lifetimes, 0.2 percent had

used it in the past year, and 0.1 percent

used in the past month. Lifetime use

declined significantly from 2003 to

2004 among persons aged 12 to 17

and 18 to 25. 

LSD Use by Students, 2005:

Monitoring the Future Survey

8th-Graders 10th-Graders 12th-Graders

Lifetime 1.9% 2.5% 3.5%

Annual 1.2 1.5 1.8

30-day 0.5 0.6 0.7
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* These data are from the 2005 Monitoring the Future survey, funded by the National Institute on Drug Abuse,

National Institutes of Health, DHHS, 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. “Annual” refers to use at least once during the

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

*** 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. Copies of the latest

survey are available at www.samhsa.gov and from the National Clearinghouse for Alcohol and Drug Information at

800-729-6686.

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.