What is marijuana?

Marijuana—often called pot,

grass, reefer, weed, herb,

mary jane, or mj—is a

greenish-gray mixture of the dried,

shredded leaves, stems, seeds,

and flowers of Cannabis sativa,

the hemp plant. Most users smoke

marijuana in hand-rolled cigarettes

called joints, among other names;

some use pipes or water pipes

called bongs. Marijuana cigars

called blunts have also become

popular. To make blunts, users

slice open cigars and replace the

tobacco with marijuana, often

combined with another drug, 

such as crack cocaine. Marijuana

also is used to brew tea and is

sometimes mixed into foods.

The major active chemical in

marijuana is delta-9-tetrahydrocannabinol (THC), which causes

the mind-altering effects of marijuana intoxication. The amount 

of THC (which is also the psychoactive ingredient in hashish) determines the potency and, therefore,

the effects of marijuana. Between

1980 and 1997, the amount of

THC in marijuana available in the

United States rose dramatically.7

What is the scope

of marijuana use in

the United States?

Marijuana is the Nation’s

most commonly used 

illicit drug. More than 

94 million Americans 

(40 percent) age 12 and

older have tried marijuana

at least once, according to

the 2003 National Survey

on Drug Use and Health

(NSDUH).

Marijuana use is widespread among adolescents

and young adults. The percentage of middle school

students who reported

using marijuana increased

throughout the early 1990s. f

r

o

m

t

h

e

dir

e

c

t

o

r

In the 1970s, the baby boom

generation was coming of age, and

its drug of choice was marijuana.

By 1979, more than 60 percent of

12th-graders had tried marijuana

at least once in their lives. From this

peak, the percentage of 12th-graders

who had ever used marijuana

decreased for more than a decade,

dropping to a low of 33 percent in

1992. However, in 1993, first-time

marijuana use by 12th-graders was

on the upswing, reaching 50 percent

by 1997. Although the percentage

of 12th-graders who have experience

with marijuana has remained

roughly level since then, there is

still reason to be concerned.1 In

2002, an estimated 2.6 million

Americans used marijuana for the

first time. Roughly two-thirds of

them were under age 18.2 Furthermore, the marijuana that is 

available today can be 5 times

more potent than the marijuana 

of the 1970s.

The use of marijuana can 

produce adverse physical, mental,

emotional, and behavioral changes,

and—contrary to popular belief—it

can be addictive. Marijuana smoke,

like cigarette smoke, can harm the

lungs.3 The use of marijuana can

impair short-term memory,4 verbal

skills, and judgment and distort

perception. It also may weaken 

the immune system5 and possibly

increase a user’s likelihood of

developing cancer. Finally, the

increasing use of marijuana by

very young teens may have a 

profoundly negative effect upon

their development.6

We hope that this research report

will help make readers aware of

our current knowledge of marijuana

abuse and its harmful effects.

Nora D.Volkow, M.D.

Director

National Institute on Drug Abuse

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

ResearchReport NATIONAL INSTITUTE ON DRUG ABUSE

SERIES

MARIJUANAAbuse
■

■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■

■ ■ ■ ■ ■ ■ ■ ■

■

In the past few years, according 

to the 2004 Monitoring the Future

Survey, an annual survey of drug

use among the Nation’s middle

and high school students, illicit

drug use by 8th-, 10th-, and 12thgraders has leveled off. Still, in

2004, 16 percent of 8th-graders

reported that they had tried 

marijuana, and 6 percent were

current users (defined as having

used the drug in the 30 days 

preceding the survey). Among

10th-graders, 35 percent had tried

marijuana sometime in their lives,

and 16 percent were current users.

As would be expected, rates of

use among 12th-graders were

higher still. Forty-six percent had

tried marijuana at some time, and

20 percent were current users.

The Drug Abuse Warning

Network (DAWN), a system for

monitoring the health impact of

drugs, estimated that, in 2002,

marijuana was a contributing factor

in over 119,000 emergency department (ED) visits in the United

States, with about 15 percent of

the patients between the ages of

12 and 17, and almost two-thirds

male.8

In 2002, the National Institute 

of Justice’s Arrestee Drug Abuse

Monitoring (ADAM) Program,

which collects data on the number

of adult arrestees testing positive

for various drugs, found that, on

average, 41 percent of adult male

arrestees and 27 percent of adult

female arrestees tested positive for

marijuana.9 On average, 57 percent

of juvenile male and 32 percent of

juvenile female arrestees tested

positive for marijuana.

NIDA’s Community Epidemiology

Work Group (CEWG), a network

of researchers that tracks trends 

in the nature and patterns of 

drug use in major U.S. cities, 

consistently reports that marijuana

frequently is combined with other

drugs, such as crack cocaine, PCP,

formaldehyde, and codeine cough

syrup, sometimes without the user

being aware of it. Thus, the risks

associated with marijuana use may

be compounded by the risks of

added drugs, as well.

How does marijuana

affect the brain?

S

cientists have learned a great

deal about how THC acts 

in the brain to produce its

many effects. When someone

smokes marijuana, THC rapidly

passes from the lungs into the

bloodstream, which carries the

chemical to organs throughout the

body, including the brain. In the

brain, THC connects to specific

sites called cannabinoid receptors

on nerve cells and thereby influences the activity of those cells.

Some brain areas have many

cannabinoid receptors; others 

have few or none. Many cannabinoid receptors are found in the

parts of the brain that influence

pleasure, memory, thought, 

concentration, sensory and time

perception, and coordinated

movement.

2NIDA RESEARCH REPORT SERIES

Long-Term Trends in Lifetime* Marijuana Use by 12th-Graders

*at least once in a lifetime

Source: The Monitoring the Future Survey, the University of Michigan

70

60

50 

40 

30

20

10

0 ’75 ’76 ’77 ’78 ’79 ’80 ’81 ’82 ’83 ’84 ’85 ’86 ’87 ’88 ’89 ’90 ’91 ’92 ’93 ’94 ’95 ’96 ’97 ’98 ’99 ’00 ’01 ’02 ’03 ’04

■ Marijuana/Hashish

Percent Ever Used

Year
What are the 

acute effects of

marijuana use?

When marijuana is smoked,

its effects begin immediately after the drug enters

the brain and last from 1 to 3

hours. If marijuana is consumed 

in food or drink, the short-term

effects begin more slowly, usually

in 1/2 to 1 hour, and last longer,

for as long as 4 hours. Smoking

marijuana deposits several times

more THC into the blood than

does eating or drinking the drug.

Within a few minutes after

inhaling marijuana smoke, an 

individual’s heart begins beating

more rapidly, the bronchial 

passages relax and become

enlarged, and blood vessels in 

the eyes expand, making the eyes

look red. The heart rate, normally

70 to 80 beats per minute, may

increase by 20 to 50 beats per

minute or, in some cases, even

double. This effect can be greater

if other drugs are taken with 

marijuana.

As THC enters the brain, it

causes a user to feel euphoric—

or “high”—by acting in the brain’s

reward system, areas of the brain

that respond to stimuli such as

food and drink as well as most

drugs of abuse. THC activates 

the reward system in the same

way that nearly all drugs of abuse

do, by stimulating brain cells to

release the chemical dopamine.

A marijuana user may experience pleasant sensations, colors

and sounds may seem more

intense, and time appears to pass

very slowly. The user’s mouth

feels dry, and he or she may 

suddenly become very hungry

and thirsty. His or her hands 

may tremble and grow cold. 

The euphoria passes after awhile,

and then the user may feel sleepy

or depressed. Occasionally, 

marijuana use produces anxiety,

fear, distrust, or panic.

Heavy marijuana use impairs a

person’s ability to form memories,

recall events (see Marijuana,

Memory, and the Hippocampus),

and shift attention from one thing

to another.10 THC also disrupts

coordination and balance by 

NIDA RESEARCH REPORT SERIES3

Marijuana’s Effects on the Brain

Frontal Lobe

Brain Stem

Cerebellum

Parietal Lobe

Cingulate Cortex

Hypothalamus

Amygdala

Hippocampus Spinal Cord

When marijuana is smoked, its active ingredient,

THC, travels throughout the body, including the

brain, to produce its many effects. THC attaches to

sites called cannabinoid receptors on nerve cells

in the brain, affecting the way those cells work.

Cannabinoid receptors are abundant in parts of

the brain that regulate movement, coordination,

learning and memory, higher cognitive functions

such as judgment, and pleasure.

Brain Region Functions Associated With Region

Brain regions in which cannabinoid receptors are abundant

Cerebellum Body movement coordination

Hippocampus Learning and memory

Cerebral cortex, especially cingulate, Higher cognitive functions

frontal, and parietal regions

Nucleus accumbens Reward

Basal ganglia Movement control

Substantia nigra pars reticulata

Entopeduncular nucleus

Globus pallidus

Putamen

Brain regions in which cannabinoid receptors are moderately concentrated

Hypothalamus Body housekeeping functions (body temperature

regulation, salt and water balance, reproductive

function)

Amygdala Emotional response, fear

Spinal cord Peripheral sensation, including pain

Brain stem Sleep and arousal, temperature regulation, 

motor control

Central gray Analgesia

Nucleus of the solitary tract Visceral sensation, nausea and vomiting
binding to receptors in the cerebellum and basal ganglia, parts 

of the brain that regulate balance,

posture, coordination of movement, and reaction time. Through

its effects on the brain and body,

marijuana intoxication can cause

accidents. Studies show that

approximately 6 to 11 percent of

fatal accident victims test positive

for THC. In many of these cases,

alcohol is detected as well.11

In a study conducted by the

National Highway Traffic Safety

Administration, a moderate dose

of marijuana alone was shown to

impair driving performance; however, the effects of even a low

dose of marijuana combined with

alcohol were markedly greater

than for either drug alone.12

Driving indices measured included

reaction time, visual search 

frequency (driver checking side

streets), and the ability to perceive

and/or respond to changes in the

relative velocity of other vehicles.

Marijuana users who have

taken high doses of the drug may

experience acute toxic psychosis,

which includes hallucinations, delusions, and depersonalization—

a loss of the sense of personal

identity, or self-recognition.

Although the specific causes of

these symptoms remain unknown,

they appear to occur more frequently when a high dose of

cannabis is consumed in food 

or drink rather than smoked.

How does marijuana

use affect physical

health?

Marijuana use has been

shown to increase users’

difficulty in trying to quit

smoking tobacco.13 This was

reported in a study comparing

smoking cessation in adults who

smoked both marijuana and

tobacco with those who smoked

only tobacco. The relationship

between marijuana use and continued smoking was particularly

strong in those who smoked 

marijuana daily at the time of the

initial interview, 13 years prior to

the followup interview.

A study of 450 individuals

found that people who smoke

marijuana frequently but do not

smoke tobacco have more health

problems and miss more days of

work than nonsmokers do. Many

of the extra sick days used by the

marijuana smokers in the study

were for respiratory illnesses.

Even infrequent marijuana use

can cause burning and stinging 

of the mouth and throat, often

accompanied by a heavy cough.

Someone who smokes marijuana

regularly may have many of the

same respiratory problems that

tobacco smokers do, such as daily

cough and phlegm production,

more frequent acute chest illnesses,

a heightened risk of lung infections, and a greater tendency

toward obstructed airways.3

Cancer of the respiratory tract

and lungs may also be promoted

by marijuana smoke.3 A study

comparing 173 cancer patients

and 176 healthy individuals 

produced strong evidence that

smoking marijuana increases the

likelihood of developing cancer 

of the head or neck, and that the

more marijuana smoked, the

greater the increase. A statistical

analysis of the data suggested that

marijuana smoking doubled or

tripled the risk of these cancers.

Marijuana has the potential to

promote cancer of the lungs and

other parts of the respiratory tract

because it contains irritants and

carcinogens. In fact, marijuana

smoke contains 50 percent to 

70 percent more carcinogenic

hydrocarbons than does tobacco

smoke. It also produces high 

levels of an enzyme that converts

certain hydrocarbons into their

carcinogenic form, levels that 

may accelerate the changes that 

ultimately produce malignant

cells. Marijuana users usually

4NIDA RESEARCH REPORT SERIES

Marijuana, Memory, and the Hippocampus

Marijuana’s damage to short-term memory seems to occurbecause THC alters the way in which information is processed by the hippocampus, a brain area responsible for memory

formation. Laboratory rats treated with THC displayed the same

reduced ability to perform tasks requiring short-term memory as

other rats showed after nerve cells in their hippocampus were destroyed. In addition, the THC-treated rats had the greatest difficulty

with the tasks precisely during the time when the drug was interfering most with the normal functioning of cells in the hippocampus.

As people age, they normally lose neurons in the hippocampus,

which decreases their ability to remember events. Chronic THC

exposure may hasten the age-related loss of hippocampal neurons.

In one series of studies, rats exposed to THC every day for 

8 months (approximately 30 percent of their lifespan), when

examined at 11 to 12 months of age, showed nerve cell loss

equivalent to that of unexposed animals twice their age.
inhale more deeply and hold their

breath longer than tobacco smokers do, which increases the lungs’

exposure to carcinogenic smoke.

These facts suggest that, puff for

puff, smoking marijuana may

increase the risk of cancer more

than smoking tobacco does.

Some adverse health effects

caused by marijuana may occur

because THC impairs the immune

system’s ability to fight off infectious diseases and cancer. In laboratory experiments that exposed

animal and human cells to THC 

or other marijuana ingredients, 

the normal disease-preventing

reactions of many of the key types

of immune cells were inhibited.5

In other studies, mice exposed to

THC or related substances were

more likely than unexposed mice

to develop bacterial infections 

and tumors.

One study has indicated that a

person’s risk of heart attack during the first hour after smoking

marijuana is four times his or her

usual risk. The researchers suggest

that a heart attack might occur,

in part, because marijuana raises

blood pressure and heart rate 

and reduces the oxygen-carrying

capacity of blood.

How does marijuana

use affect school,

work, and social life?

S

tudents who smoke marijuana

get lower grades and are less

likely to graduate from high

school, compared with their nonsmoking peers.6, 14

Workers who smoke marijuana

are more likely than their coworkers to have problems on the

job. Several studies have associated

workers’ marijuana smoking with

increased absences, tardiness,

accidents, workers’ compensation

claims, and job turnover. A study

among postal workers found that

employees who tested positive 

for marijuana on a pre-employment

urine drug test had 55 percent more

industrial accidents, 85 percent

more injuries, and a 75-percent

increase in absenteeism compared

with those who tested negative for

marijuana use.

Depression, anxiety, and 

personality disturbances are all 

associated with marijuana use.

Research clearly demonstrates that

marijuana use has the potential 

to cause problems in daily life or

make a person’s existing problems

worse. Because marijuana compromises the ability to learn and

remember information, the more a

person uses marijuana the more

NIDA RESEARCH REPORT SERIES5

Health Consequences of Marijuana Abuse

Acute (present during intoxication)

■ Impairs short-term memory

■ Impairs attention, judgment, and other cognitive functions

■ Impairs coordination and balance

■ Increases heart rate

Persistent (lasting longer than intoxication, but may not be permanent)

■ Impairs memory and learning skills

Long-term (cumulative, potentially permanent effects of chronic abuse)

■ Can lead to addiction

■ Increases risk of chronic cough, bronchitis, and emphysema

■ Increases risk of cancer of the head, neck, and lungs

The Science of 

Medical Marijuana

THC,the main active 

ingredient in marijuana, produces effects that

potentially can be useful for

treating a variety of medical

conditions. It is the main ingredient in an oral medication 

that is currently used to treat

nausea in cancer chemotherapy

patients and to stimulate

appetite in patients with wasting

due to AIDS. Scientists are

continuing to investigate other

potential medical uses for

cannabinoids.22

Research is underway to 

examine the effects of smoked

marijuana and extracts of 

marijuana on appetite stimulation, certain types of pain,

and spasticity due to multiple

sclerosis. However, the inconsistency of THC dosage in 

different marijuana samples

poses a major hindrance to

valid trials and to the safe 

and effective use of the drug.

Moreover, the adverse effects 

of marijuana smoke on the 

respiratory system3 will offset 

the helpfulness of smoked marijuana for some patients. Finally,

little is known about the many

chemicals besides THC that are

in marijuana, or their possible

deleterious impact on patients

with medical conditions.
he or she is likely to fall behind 

in accumulating intellectual, job,

or social skills. In one study of

cognition, adults were matched 

on the basis of their performance

in the 4th grade on the Iowa Test

of Basic Skills. They were evaluated on a number of cognitive

measures including the 12th-grade

version of the Iowa Test. Those

who were heavy marijuana

smokers scored significantly lower

on mathematical skills and verbal

expression than nonsmokers. 

Moreover, research has shown

that marijuana’s adverse impact 

on memory and learning can last

for days or weeks after the acute

effects of the drug wear off.16 For

example, a study of 129 college

students found that among heavy

users of marijuana—those who

smoked the drug at least 27 of 

the preceding 30 days—critical

skills related to attention, memory,

and learning were significantly

impaired, even after they had 

not used the drug for at least 

24 hours.10 The heavy marijuana

users in the study had more trouble sustaining and shifting their

attention and in registering, organizing, and using information than

did the study participants who

had used marijuana no more than

3 of the previous 30 days. As a

result, someone who smokes 

marijuana once daily may be functioning at a reduced intellectual

level all of the time. More recently,

the same researchers showed 

that a group of long-term heavy

marijuana users’ ability to recall

words from a list was impaired 

1 week following cessation of

marijuana use, but returned to

normal by 4 weeks.16 An implication of this finding is that even

after long-term heavy marijuana

use, if an individual quits marijuana

use, some cognitive abilities may

be recovered.

Another study produced additional evidence that marijuana’s

effects on the brain can cause

cumulative deterioration of 

critical life skills in the long run.

Researchers gave students a battery

of tests measuring problem-solving

and emotional skills in 8th grade

and again in 12th grade. The

results showed that the students

who were already drinking 

alcohol plus smoking marijuana 

in 8th grade started off slightly

behind their peers, but that the

distance separating these two

groups grew significantly by 

their senior year in high school.

The analysis linked marijuana 

use, independently of alcohol 

use, to reduced capacity for selfreinforcement, a group of psychological skills that enable individuals

to maintain confidence and 

persevere in the pursuit of goals.

Marijuana users themselves

report poor outcomes on a variety

of measures of life satisfaction and

achievement. A recent study compared current and former longterm heavy users of marijuana 

with a control group who reported

smoking cannabis at least once 

in their lives, but not more than

50 times. Despite similar education and incomes in their families

of origin, significant differences

were found in educational attainment and income between heavy

users and the control group: fewer

of the cannabis users completed

college and more had household

incomes of less than $30,000.

When asked how marijuana

affected their cognitive abilities,

career achievements, social lives,

and physical and mental health,

the overwhelming majority of

heavy cannabis users reported 

the drug’s deleterious effect on 

all of these measures.

Can marijuana use

during pregnancy

harm the baby?

Research has shown that

some babies born to women 

who used marijuana during

their pregnancies display altered

responses to visual stimuli,

increased tremulousness, and 

a high-pitched cry, which may

indicate problems with neurological development. During the 

preschool years, marijuanaexposed children have been

observed to perform tasks 

involving sustained attention 

and memory more poorly than

nonexposed children do.17 In the

school years, these children are

more likely to exhibit deficits in

problem-solving skills, memory,

and the ability to remain

attentive.17

Is marijuana 

use addictive?

L

ong-term marijuana use can

lead to addiction for some

people; that is, they use the

drug compulsively even though it

often interferes with family, school,

work, and recreational activities.

According to the 2003 National

Survey on Drug Use and Health

(NSDUH), an estimated 21.6 million

Americans aged 12 or older were

classified with substance dependence or abuse (9.1 percent of the

total population). Of the estimated

6.9 million Americans classified

with dependence on or abuse of

illicit drugs, 4.2 million were

dependent on or abused marijuana.

In 2002, 15 percent of people

entering drug abuse treatment

programs reported that marijuana

was their primary drug of abuse.

6NIDA RESEARCH REPORT SERIES
Along with craving, withdrawal

symptoms can make it hard for

long-term marijuana smokers to

stop using the drug.15 People 

trying to quit report irritability, 

difficulty sleeping, and anxiety.

They also display increased

aggression on psychological tests,

peaking approximately 1 week

after they last used the drug.

In addition to its addictive 

liability, research indicates that

early exposure to marijuana can

increase the likelihood of a lifetime of subsequent drug problems.

A recent study of over 300 fraternal and identical twin pairs, who

differed on whether or not they

used marijuana before the age of

17, found that those who had

used marijuana early had elevated

rates of other drug use and drug

problems later on, compared with

their twins, who did not use marijuana before age 17. This study

re-emphasizes the importance of

primary prevention by showing

that early drug initiation is associated with increased risk of later

drug problems, and it provides

more evidence for why preventing

marijuana experimentation during

adolescence could have an impact

on preventing addiction.18

What treatments 

are available for

marijuana abusers?

T

reatment programs directed

solely at marijuana abuse are

rare, partly because many

who use marijuana do so in combination with other drugs, such as

cocaine and alcohol. However,

with more people seeking help to

control marijuana abuse, research

has focused on ways to overcome

problems with abuse of this drug.

One study of adult marijuana

users found comparable benefits

from a 14-session cognitivebehavioral group treatment and a

2-session individual treatment that

included motivational interviewing

and advice on ways to reduce

marijuana use. Participants were

mostly men in their early thirties

who had smoked marijuana daily

for over 10 years. By increasing

patients’ awareness of what triggers

their marijuana use, both treatments sought to help them devise

avoidance strategies. Use, dependence symptoms, and psychosocial

problems decreased for at least 

1 year after both treatments. About

30 percent of users were abstinent

during the last 3-month followup

period. Another study suggests

that giving patients vouchers for

abstaining from marijuana can

improve outcomes.19 Vouchers can

be redeemed for such goods as

movie passes, sports equipment,

or vocational training.

No medications are now available to treat marijuana abuse.

However, recent discoveries about

the workings of THC receptors

have raised the possibility that 

scientists may eventually develop

a medication that will block THC’s

intoxicating effects. Such a medication might be used to prevent

relapse to marijuana abuse by

reducing or eliminating its appeal.

Where can I get

further scientific

information about

marijuana?

T

o learn more about marijuana

and other drugs of abuse,

contact the National

Clearinghouse for Alcohol and

Drug Information (NCADI) at 

1-800-729-6686. Information specialists are available to help you

locate information and resources.

Fact sheets, including InfoFacts,

on the health effects of marijuana,

other drugs of abuse, and 

other drug abuse topics are

available on the NIDA Web site 

(www.drugabuse.gov), and can 

be ordered free of charge in

English and Spanish from NCADI

at www.health.org.

NIDA RESEARCH REPORT SERIES7

The Body’s Natural

THC-Like Chemicals

THC owes many of itseffects to its similarity

to a family of chemicals called

the endogenous cannabinoids,

which are natural Cannabislike chemicals. Because a THC

molecule is shaped like these

endogenous cannabinoids, 

it interacts with the same

receptors on nerve cells, the

cannabinoid receptors, that

endogenous cannabinoids do,

and it influences many of the

same processes. Research has

shown that the endogenous

cannabinoids help control a

wide array of mental and

physical processes in the brain

and throughout the body,

including memory and perception, fine motor coordination, pain sensations, immunity

to disease, and reproduction.

When someone smokes 

marijuana, THC overstimulates

the cannabinoid receptors,

leading to a disruption of the

endogenous cannabinoids’

normal function. This overstimulation produces the 

intoxication experienced by

marijuana smokers. Over

time, it may alter the function

of cannabinoid receptors,

which, along with other

changes in the brain, can

lead to withdrawal symptoms

and addiction.20, 21
References

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Johnston, L.D.; O’Malley, P.M.; and Bachman, J.G.

Monitoring the Future: National Results on

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Substance Abuse and Mental Health Services

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Survey on Drug Use and Health: National

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Tashkin, D.P. Pulmonary complications of smoked

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Heishman, S.J.; Arasteh, K.; and Stitzer, M.L.

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ElSohly, M.A.; Ross, S.A.; Mehmedic, Z.; Arafat, R.;

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National Institute of Justice, Arrestee Drug Abuse

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U.S. Department of Justice, 2002.

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cognitive effects of heavy marijuana use in 

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11

Cimbura, G.; Lucas, D.M.; Bennett, R.C.; and

Donelson, A.C. Incidence and toxicological 

aspects of cannabis and ethanol detected in

1,394 fatally injured drivers and pedestrians 

in Ontario (1982–1984). J Forensic Sci

35:1035–1041, 1990.

12National Highway Traffic Safety Administration

(NHTSA) Notes. Marijuana and alcohol 

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Annals Emer Med 35(4):398–399, 2000.

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from a community sample. Drug Alc Depend

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review. Addiction 95(11):1621–1630, 2000.

15 Budney, A.J.; Moore, B.A.; Vandrey, R.G.; and

Hughes, J.R. The time course and significance 

of cannabis withdrawal. J Abnorm Psychol

112(3):393–402, 2003.

16 Pope, H.G.; Gruber, A.J.; Hudson, J.I.; Huestis,

M.A.; and Yurgelun-Todd, D. Neuropsychological

performance in long-term cannabis users. 

Arch Gen Psychiatry 58(10):909–915, 2001.

17 Fried, P.A.; and Smith, A.M. A literature review 

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W.S.; Madden, P.A.F.; Nelson, E.C.; Statham,

D.J.; and Martin, N.G. Escalation of drug use in

early-onset cannabis users vs. co-twin controls.

JAMA 289:427–433, 2003.

19

Budney, A.J.; Higgins, S.T.; Radonovich, K.J.; and

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68(6):1051–1061, 2000.

20Maldonado, R.; and de Fonseca, F.R. Cannabinoid

addiction: Behavioral models and neural correlates.

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21 Breivogel, C.S.; Scates, S.M.; Beletskaya, I.O.;

Lowery, O.B.; Aceto, M.D.; and Martin, B.R. The

effects of delta-9 tetrahydrocannabinol physical

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Access information 

on the Internet

• What’s new on the NIDA Web site

• Information on drugs of abuse

• Publications and communications

(including NIDA NOTES)

• Calendar of events

• Links to NIDA organizational units

• Funding information 

(including program announcements 

and deadlines)

• International activities

• Links to related Web sites 

(access to Web sites of many other

organizations in the field)

NIDA Web Sites

www.drugabuse.gov

www.marijuana-info.org

www.steroidabuse.org

www.clubdrugs.org

NCADI

Web Site: www.health.org

Phone No.: 1-800-729-6686

8NIDA RESEARCH REPORT SERIES

Glossary

Addiction: A chronic, relapsing disease characterized by compulsive drug-seeking and abuse and

by long-lasting chemical changes in the brain.

Cannabinoids: Chemicals that help control mental

and physical processes when produced naturally 

by the body and that produce intoxication and

other effects when absorbed from marijuana.

Carcinogen: Any substance that causes cancer.

Dopamine: A brain chemical, classified as a 

neurotransmitter, found in regions of the brain

that regulate movement, emotion, motivation, 

and pleasure.

Hippocampus: An area of the brain crucial for

learning and memory.

Hydrocarbon: Any chemical compound containing only hydrogen and carbon.

Psychoactive: Having a specific effect on the mind.

THC: Delta-9-tetrahydrocannabinol; the main

active ingredient in marijuana, which acts on the

brain to produce its effects.

Withdrawal: Symptoms that occur after use of a

drug is reduced or stopped.

NIH Publication Number 05-3859

Printed October 2002, Reprinted March 2003, 

Printed July 2005.

Feel free to reprint this publication.