What Is 

Marijuana?

from the director:

By the time they graduate from 

high school, about 46 percent of 

teens will have tried marijuana.1

Although current use among U.S. 

teens dropped dramatically in 

the past decade (to a prevalence 

of about 15 percent in 2011), this 

decline has stalled during the past 

several years.2

 These data are 

from the Monitoring the Future 

survey, which has been tracking 

drug use among teens since 1975. 

Still, the World Health Organization ranks the United States first 

among 17 European and North 

American countries for prevalence of marijuana use. And more 

users start every day. In 2010, an 

estimated 2.4 million Americans 

used marijuana for the first time; 

greater than one-half were under 

age 18.1

The use of marijuana can produce 

adverse physical, mental, emotional, and behavioral effects. It 

can impair short-term memory 

and judgment and distort perception. Because marijuana affects 

brain systems that are still maturing through young adulthood, its 

use by teens may have a negative 

effect on their development. And 

contrary to popular belief, it can 

be addictive.

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 

How does marijuana 

use affect school, 

work, and social life?

See page 7.

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, or blunts, are 

also popular. To make blunts, users slice open cigars, remove some 

of the tobacco, and mix the remainder with marijuana.3

 Marijuana 

also is used to brew tea and sometimes is mixed into foods.

continued inside

Marijuana 

Abuse
Research Report Series

What Is the 

Scope of 

Marijuana Use 

in the United 

States?

Marijuana is the most commonly 

used illicit drug (17.4 million 

past-month users) according to the 

2010 National Survey on Drug Use 

and Health (NSDUH).1 That year, 

marijuana was used by 76.8 percent 

of current illicit drug users (defined 

as having used the drug at some time 

in the 30 days before the survey) 

and was the only drug used by 60.1 

percent of them.1

Marijuana use is widespread 

among adolescents and young adults. 

According to the Monitoring the 

Future Survey—an annual survey 

of attitudes and drug use among the 

Nation’s middle and high school students—most measures of marijuana 

use decreased in the past decade 

among 8th-, 10th-, and 12th-graders. 

However, this decline has stalled in 

the past few years as attitudes have 

softened about marijuana’s risks. In 

2011, 12.5 percent of 8th-graders reported marijuana use in the past year, 

and 7.2 percent were current users. 

Among 10th-graders, 28.8 percent 

had used marijuana in the past year, 

and 17.6 percent were current users. 

Rates of use among 12th-graders 

were higher still: 36.4 percent had 

used marijuana during the year prior 

to the survey, and 22.6 percent were 

current users.2

The Drug Abuse Warning Network (DAWN), a system for monitoring the health impact of drugs, 

estimated that in 2009, marijuana 

was a contributing factor in over 

376,000 emergency department (ED) 

visits in the United States, with about 

two-thirds of patients being male, 

and 12 percent between the ages of 

12 and 17.4

How Does 

Marijuana 

Produce its 

Effects? 

Delta-9-tetrahydrocannabinol (THC) 

is the main active ingredient in 

marijuana, responsible for many of 

its known effects. When marijuana 

is smoked, its effects begin almost 

immediately. THC rapidly passes 

from the lungs into the bloodstream, 

which carries the chemical to organs 

throughout the body, including 

the brain. The effects of smoked 

marijuana can last from 1 to 3 hours. 

If marijuana is consumed in foods or 

beverages, the effects appear later—

usually in 30 minutes to 1 hour—but 

can last up to 4 hours. Smoking 

marijuana delivers significantly 

more THC into the bloodstream than 

eating or drinking the drug. 

Long-Term Trends in Annual* Marijuana Use 

Among 8th-, 10th-, and 12th-Graders

*use in the past 12 months

Source: University of Michigan, 2011 Monitoring the Future Survey.

8th-graders

10th-graders

12th-graders

Percent

1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 10

15

20

25

30

35

40

2 NIDA Research Report Series

Marijuana

Abuse
Scientists have learned a great 

deal about how THC acts in the 

brain. THC binds to specific sites 

called cannabinoid receptors (CBRs) 

located on the surface of nerve 

cells. These receptors are found in 

high-density in areas of the brain 

that influence pleasure, memory, 

thinking, concentration, movement, 

coordination, and sensory and time 

perception. 

CBRs are part of a vast 

communication network known 

as the endocannabinoid system, 

which plays a critical role in normal 

brain development and function. 

In fact, THC effects are similar 

to those produced by naturally 

occurring chemicals found in the 

brain (and body) called endogenous 

cannabinoids. These chemicals help 

control many of the same mental 

and physical functions that may be 

disrupted by marijuana use.

When someone smokes 

marijuana, THC stimulates the 

CBRs artificially, disrupting function 

of the natural, or endogenous, 

cannabinoids. An overstimulation 

of these receptors in key brain 

areas produces the marijuana 

“high,” as well as other effects 

on mental processes. Over time, 

this overstimulation can alter the 

function of CBRs, which, along 

with other changes in the brain, can 

lead to addiction and to withdrawal 

symptoms when drug use stops.

 The THC content or potency of 

marijuana, as detected in confiscated 

samples over the past 30+ years, 

has been steadily increasing.5

 This 

increase raises concerns that the 

consequences of marijuana use 

could be worse than in the past, 

particularly among new users, or in 

young people, whose brains are still 

developing. We still do not know, 

however, whether cannabis users 

adjust for the increase in potency 

by using less or by smoking it 

differently. We also do not know 

all the consequences to the brain 

and body when exposed to higher 

concentrations of THC.

How Does 

Marijuana Use 

Affect Your Brain 

and Body?

Effects on the Brain

As THC enters the brain, it causes 

the user to feel euphoric—or 

high—by acting on the brain’s 

reward system, which is made up 

of regions that govern the response 

to pleasurable things like sex and 

chocolate, as well as to most drugs 

of abuse. THC activates the reward 

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.

Marijuana’s Effects on the Brain

© Alice Y. Chen, 2004. Adapted from Scientific American.

NIDA Research Report Series 3
Marijuana users who have taken large doses of the drug may 

experience an acute psychosis, which includes hallucinations, 

delusions, and a loss of the sense of personal identity. 

have been associated with the use of 

cannabis in vulnerable individuals. 

(See section on the link between 

marijuana use and mental illness, 

page 6.)

Our understanding of 

marijuana’s long-term brain effects 

is limited. Research findings on 

how chronic cannabis use affects 

brain structure, for example, 

have been inconsistent. It may 

be that the effects are too subtle 

for reliable detection by current 

techniques. A similar challenge 

arises in studies of the effects of 

chronic marijuana use on brain 

function. Although imaging studies 

(functional MRI; fMRI) in chronic 

users do show some consistent 

alterations, the relation of these 

system in the same way that nearly 

all drugs of abuse do: by stimulating 

brain cells to release the chemical 

dopamine. 

Along with euphoria, relaxation 

is another frequently reported effect 

in human studies. Other effects, 

which vary dramatically among 

different users, include heightened 

sensory perception (e.g., brighter 

colors), laughter, altered perception 

of time, and increased appetite. 

After a while, the euphoria subsides, 

and the user may feel sleepy or 

depressed. Occasionally, marijuana 

use may produce anxiety, fear, 

distrust, or panic.

Marijuana use impairs a person’s 

ability to form new memories (see 

below, “Marijuana, Memory, 

and the Hippocampus”) and to 

shift focus. THC also disrupts 

coordination and balance by binding 

to receptors in the cerebellum 

and basal ganglia—parts of 

the brain that regulate balance, 

posture, coordination, and reaction 

time. Therefore, learning, doing 

complicated tasks, participating 

in athletics, and driving are also 

affected. 

Marijuana users who have 

taken large doses of the drug may 

experience an acute psychosis, which 

includes hallucinations, delusions, 

and a loss of the sense of personal 

identity. Short-term psychotic 

reactions to high concentrations of 

THC are distinct from longer-lasting, 

schizophrenia-like disorders that 

Memory impairment from 

marijuana use occurs because 

THC alters how information is 

processed in the hippocampus, 

a brain area responsible for 

memory formation.

Most of the evidence supporting 

this assertion comes from 

animal studies. For example, 

rats exposed to THC in utero, 

soon after birth, or during 

adolescence, show notable 

problems with specific learning/

memory tasks later in life. 

Moreover, cognitive impairment 

in adult rats is associated 

with structural and functional 

changes in the hippocampus 

from THC exposure during 

adolescence.

As people age, they lose 

neurons in the hippocampus, 

which decreases their ability to 

learn new information. Chronic 

THC exposure may hasten agerelated loss of hippocampal 

neurons. In one study, rats 

exposed to THC every day 

for 8 months (approximately 

30 percent of their life-span) 

showed a level of nerve cell 

loss (at 11 to 12 months of age) 

that equaled that of unexposed 

animals twice their age. 

Marijuana, Memory, and 

the Hippocampus

Distribution of cannabinoid receptors in the rat 

brain. Brain image reveals high levels (shown in 

orange and yellow) of cannabinoid receptors in 

many areas, including the cortex, hippocampus, 

cerebellum, and nucleus accumbens (ventral 

striatum).

4 NIDA Research Report Series
Within a few minutes after inhaling marijuana 

smoke, an individual’s heart rate speeds up, 

the bronchial passages relax and become 

enlarged, and blood vessels in the eyes 

expand, making the eyes look red. 

Limited evidence suggests that 

a person’s risk of heart attack during 

the first hour after smoking marijuana is four times his or her usual 

risk. This observation could be partly 

explained by marijuana raising blood 

pressure (in some cases) and heart 

rate and reducing the blood’s capacity to carry oxygen. Such possibilities 

need to be examined more closely, 

particularly since current marijuana 

users include adults from the baby 

boomer generation, who may have 

other cardiovascular risks that may 

increase their vulnerability. 

The smoke of marijuana, like 

that of tobacco, consists of a toxic 

mixture of gases and particulates, 

many of which are known to be 

harmful to the lungs. 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, and a greater risk 

of lung infections. Even infrequent 

marijuana use can cause burning and 

stinging of the mouth and throat, 

often accompanied by a heavy 

changes to cognitive functioning 

is less clear. This uncertainty may 

stem from confounding factors 

such as other drug use, residual 

drug effects (which can occur for at 

least 24 hours in chronic users), or 

withdrawal symptoms in long-term 

chronic users. 

An enduring question in the 

field is whether individuals who quit 

marijuana, even after long-term, 

heavy use, can recover some of their 

cognitive abilities. One study reports 

that the ability of long-term heavy 

marijuana users to recall words 

from a list was still impaired 1 week 

after they quit using, but returned 

to normal by 4 weeks. However, 

another study found that marijuana’s 

effects on the brain can build up and 

deteriorate critical life skills over 

time. Such effects may be worse in 

those with other mental disorders, or 

simply by virtue of the normal aging 

process. 

Effects on General 

Physical Health

Within a few minutes after inhaling 

marijuana smoke, an individual’s 

heart rate speeds up, 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 may even 

double in some cases. Taking other 

drugs with marijuana can amplify 

this effect. 

Acute (present during intoxication)

•	 Impairs short-term memory

•	 Impairs attention, judgment, and other cognitive functions

•	 Impairs coordination and balance

•	 Increases heart rate

•	 Psychotic episodes

Persistent (lasting longer than intoxication, 

but may not be permanent)

•	 Impairs memory and learning skills

•	 Sleep impairment

Long-term (cumulative effects of chronic abuse)

•	 Can lead to addiction

•	 Increases risk of chronic cough, bronchitis

•	 Increases risk of schizophrenia in vulnerable individuals

•	 May increase risk of anxiety, depression, and amotivational 

syndrome*

* These are often reported co-occurring symptoms/disorders with chronic 

marijuana use. However, research has not yet determined whether 

marijuana is causal or just associated with these mental problems.

Consequences of 

Marijuana Abuse

NIDA Research Report Series 5
smokers generally inhale more 

deeply and hold their breath longer 

than tobacco smokers, the lungs 

are exposed longer to carcinogenic 

smoke. However, while several 

lines of evidence have suggested 

that marijuana use may lead to lung 

cancer, the supporting evidence is 

inconclusive.8 The presence of an 

unidentified active ingredient in 

cannabis smoke having protective 

properties—if corroborated and 

properly characterized—could help 

explain the inconsistencies and 

modest findings.

A significant body of research 

demonstrates negative effects of 

THC on the function of various 

immune cells, both in vitro in 

cells and in vivo with test animals. 

However, no studies to date connect 

marijuana’s suspected immune 

system suppression with greater 

incidence of infections or immune 

disorders in humans. One short 

(3-week) study found marijuana 

smoking to be associated with a 

few statistically significant negative 

effects on the immune function of 

AIDS patients; a second small study 

of college students also suggested 

the possibility of marijuana having 

adverse effects on immune system 

functioning. Thus, the combined 

evidence from animal studies plus 

the limited human data available 

seem to warrant additional research 

on the impact of marijuana on the 

immune system. (See also “The 

Science of Medical Marijuana,” 

page 9.)

Is There a 

Link Between 

Marijuana Use 

and Mental 

Illness?

Research in the past decade has 

focused on whether marijuana 

use actually causes other mental 

illnesses. The strongest evidence 

to date suggests a link between 

cannabis use and psychosis.9

For example, a series of large 

prospective studies that followed a 

group of people over time showed a 

relationship between marijuana use 

and later development of psychosis. 

Marijuana use also worsens the 

course of illness in patients with 

schizophrenia and can produce a 

cough. One study found that extra 

sick days used by frequent marijuana 

smokers were often because of 

respiratory illnesses.6

In addition, marijuana has 

the potential to promote cancer 

of the lungs and other parts of the 

respiratory tract because it contains 

irritants and carcinogens—up 

to 70 percent more than tobacco 

smoke. It also induces high levels 

of an enzyme that converts certain 

hydrocarbons into their cancercausing form, which could accelerate 

the changes that ultimately produce 

malignant cells. And since marijuana 

20

15

10

5

0

COMT genotype

No adolescent cannabis use

Adolescent cannabis use

Percent with schizophrenifor

m

disorder at age 26

Met/Met

n= (151) (48)

Val/Met

(311) (91)

Val/Val

(148) (54)

Genetic variation in COMT influences

the harmful effects of abused drugs

The influence of adolescent marijuana use on adult psychosis is affected 

by genetic variables. This figure shows that variations in a gene can 

affect the likelihood of developing psychosis in adulthood, following 

exposure to cannabis in adolescence. The COMT gene governs an 

enzyme that breaks down dopamine, a brain chemical involved in 

schizophrenia. It comes in two forms: “Met” and “Val.” Individuals with 

one or two copies of the Val variant have a higher risk of developing 

schizophrenic-type disorders if they used cannabis during adolescence 

(dark bars). Those with only the Met variant were unaffected by cannabis 

use.7

 

6 NIDA Research Report Series
brief psychotic reaction in some 

users that fades as the drug wears 

off. The amount of drug used, 

the age at first use, and genetic 

vulnerability can all influence this 

relationship. One example is a study 

(illustrated, page 6) that found an 

increased risk of psychosis among 

adults who had used marijuana in 

adolescence and who also carried 

a specific variant of the gene for 

catechol-O-methyltransferase 

(COMT), an enzyme that degrades 

neurotransmitters such as dopamine 

and norepinephrine.7

In addition to the observed 

links between marijuana use 

and schizophrenia, other less 

consistent associations have been 

reported between marijuana use 

and depression, anxiety, suicidal 

thoughts among adolescents, and 

personality disturbances. One of the 

most frequently cited, albeit still 

controversial, is an amotivational 

syndrome, defined as a diminished 

or absent drive to engage in typically 

rewarding activities. Because of 

the role of the endocannabinoid 

system in regulating mood, these 

associations make a certain amount 

of sense; however, more research 

is needed to confirm and better 

understand these linkages. 

Is Marijuana 

Addictive? 

Long-term marijuana use can lead 

to addiction; that is, people have 

difficulty controlling their drug 

use and cannot stop even though it 

interferes with many aspects of their 

lives. It is estimated that 9 percent 

of people who use marijuana will 

become dependent on it. The number 

goes up to about 1 in 6 in those who 

start using young (in their teens) 

and to 25–50 percent among daily 

users. Moreover, a study of over 300 

fraternal and identical twin pairs 

found that the twin who had used 

marijuana before the age of 17 had 

elevated rates of other drug use and 

drug problems later on, compared 

with their twin who did not use 

before age 17. 

According to the 2010 NSDUH, 

marijuana accounted for 4.5 

million of the estimated 7.1 million 

Americans dependent on or abusing 

illicit drugs.1

 In 2009, approximately 

18 percent of people aged 12 and 

older entering drug abuse treatment 

programs reported marijuana as their 

primary drug of abuse.10

Marijuana addiction is also 

linked to a withdrawal syndrome 

similar to that of nicotine 

withdrawal, which can make it 

hard to quit. People trying to 

quit report irritability, sleeping 

difficulties, craving, and anxiety. 

They also show increased aggression 

on psychological tests, peaking 

approximately 1 week after they last 

used the drug. 

How Does 

Marijuana Use 

Affect School, 

Work, and 

Social Life? 

Research has shown that marijuana’s 

negative effects on attention, 

memory, and learning can last for 

days or weeks after the acute effects 

of the drug wear off.11 Consequently, 

someone who smokes marijuana 

daily may be functioning at a 

reduced intellectual level most or 

all of the time. Not surprisingly, 

evidence suggests that, compared 

with their nonsmoking peers, 

students who smoke marijuana tend 

to get lower grades and are more 

likely to drop out of high school.12

A meta-analysis of 48 relevant 

studies—one of the most thorough 

performed to date—found cannabis 

use to be associated consistently with 

reduced educational attainment (e.g., 

grades and chances of graduating).13

However, a causal relationship is 

not yet proven between cannabis use 

by young people and psychosocial 

harm. 

That said, marijuana users 

themselves report poor outcomes 

on a variety of life satisfaction 

and achievement measures. One 

study compared current and 

former long-term 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 income backgrounds, 

significant differences were found in 

educational attainment: fewer of the 

heavy users of cannabis completed 

college, and more had yearly 

household incomes of less than 

$30,000. When asked how marijuana 

NIDA Research Report Series 7
affected their cognitive abilities, 

career achievements, social lives, 

and physical and mental health, the 

majority of heavy cannabis users 

reported the drug’s negative effects 

on all of these measures. In addition, 

several studies have linked workers’ 

marijuana smoking with increased 

absences, tardiness, accidents, 

workers’ compensation claims, and 

job turnover. For example, 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.

Does Marijuana 

Use Affect 

Driving?

Because marijuana impairs judgment 

and motor coordination and slows 

reaction time, an intoxicated person 

has an increased chance of being 

involved in and being responsible 

for an accident.14, 15 According to 

the National Highway Traffic Safety 

Administration, drugs other than 

alcohol (e.g., marijuana and cocaine) 

are involved in about 18 percent of 

motor vehicle driver deaths. A recent 

survey found that 6.8 percent of 

drivers, mostly under age 35, who 

were involved in accidents tested 

positive for THC; alcohol levels 

above the legal limit were found in 

21 percent of such drivers. 

Can Marijuana 

Use During 

Pregnancy Harm 

the Baby? 

Animal research suggests that the 

body’s endocannabinoid system 

plays a role in the control of brain 

maturation, particularly in the 

development of emotional responses. 

It is conceivable that even low 

concentrations of THC, when 

administered during the perinatal 

period, could have profound and 

long-lasting consequences for both 

brain and behavior.16 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 could indicate problems 

with neurological development. In 

school, marijuana-exposed children 

are more likely to show gaps in 

problemsolving skills, memory, and 

the ability to remain attentive. More 

research is needed, however, to 

disentangle the drug-specific factors 

from the environmental ones.17

Available 

Treatments for 

Marijuana Use 

Disorders 

Marijuana dependence appears 

to be very similar to other substance 

dependence disorders, although the 

long-term clinical outcomes may 

be less severe. On average, adults 

seeking treatment for marijuana 

abuse or dependence have used 

marijuana nearly every day for more 

than 10 years and have attempted 

to quit more than six times. It is 

important to note that marijuana 

dependence is most prevalent 

among patients suffering from other 

psychiatric disorders, particularly 

among adolescent and young adult 

populations.18 Also, marijuana abuse 

or dependence typically co-occurs 

with use of other drugs, such as 

cocaine and alcohol. Available 

studies indicate that effectively 

treating the mental health disorder 

with standard treatments involving 

medications and behavioral therapies 

may help reduce cannabis use, 

particularly among heavy users and 

those with more chronic mental 

disorders. Behavioral treatments, 

such as motivational enhancement 

therapy (MET), group or individual 

cognitive-behavioral therapy (CBT), 

and contingency management (CM), 

as well as family-based treatments, 

have shown promise. 

Unfortunately, the success rates 

of treatment are rather modest. Even 

with the most effective treatment 

for adults, only about 50 percent of 

8 NIDA Research Report Series
enrollees achieve an initial 2-week 

period of abstinence, and among 

those who do, approximately half 

will resume use within a year. 

Across studies, 1-year abstinence 

rates have ranged between 10 

and 30 percent for the various 

behavioral approaches. As with 

other addictions, these data suggest 

that a chronic care model should be 

considered for marijuana addiction, 

with treatment intensity stepped up 

or down based on need, comorbid 

addictions or other mental disorders, 

and the availability of family and 

other supports. 

Currently, no medications 

are available to treat marijuana 

abuse, but research is active in 

this area. Most of the studies to 

date have targeted the marijuana 

withdrawal syndrome. For example, 

a recent human study showed that 

a combination of a cannabinoid 

agonist medication with lofexidine 

(a medication approved in the 

United Kingdom for the treatment 

of opioid withdrawal) produced 

more robust improvements in 

sleep and decreased marijuana 

withdrawal, craving, and relapse 

in daily marijuana smokers 

relative to either medication alone. 

Recent discoveries about the 

inner workings of the endogenous 

cannabinoid system raise the future 

possibility of a medication able to 

block THC’s intoxicating effects, 

which could help prevent relapse by 

reducing or eliminating marijuana’s 

appeal. 

The Science of Medical Marijuana

The potential medicinal properties of marijuana have been the 

subject of substantive research and heated debate. Scientists have 

confirmed that the cannabis plant contains active ingredients 

with therapeutic potential for relieving pain, controlling nausea, 

stimulating appetite, and decreasing ocular pressure. As a result, 

a 1990 Institute of Medicine report concluded that further clinical 

research on cannabinoid drugs and safe delivery systems was 

warranted. 

At that time, dronabinol (Marinol®) and nabilone (Cesamet®) 

were the only FDA-approved, marijuana-based medications that 

doctors could prescribe for the treatment of nausea in patients 

undergoing cancer chemotherapy and to stimulate appetite 

in patients with wasting syndrome due to AIDS. These pills 

contained synthetic versions of THC, the main active ingredient in 

marijuana. Today, 25 years after their approval, the development 

of Sativex® marks the arrival of the second generation of 

cannabis-based medications. This new product (currently 

available in the United Kingdom and Canada) is a chemically pure 

mixture of plant-derived THC and Cannabidiol, formulated as a 

mouth spray and approved for the relief of cancer-associated pain 

and spasticity and neuropathic pain in multiple sclerosis. 

Scientists continue to investigate the medicinal properties of 

THC and other cannabinoids to better evaluate and harness 

their ability to help patients suffering from a broad range 

of conditions, while avoiding the adverse effects of smoked 

marijuana. These efforts are bound to improve our understanding 

of the cannabinoid system and help us bring to market a new 

generation of safe and effective medications. 

NIDA Research Report Series 9
Glossary

Addiction: A chronic, relapsing disease 

characterized by compulsive drug seeking and 

abuse despite adverse consequences. It is 

associated with long-lasting changes in the brain. 

Basal Ganglia: Structures located deep in the 

brain that play an important role in the initiation 

of movements. These clusters of neurons include 

the caudate nucleus, putamen, globus pallidus, 

and substantia nigra. It also contains the nucleus 

accumbens, which is the main center of reward in 

the brain. 

Cannabinoids and Cannabinoid Receptors:

A family of chemicals that bind to specific 

(cannabinoid) receptors to influence mental 

and physical functions. Cannabinoids that are 

produced naturally by the body are referred to as 

endocannabinoids. They play important roles in 

development, memory, pain, appetite, among others. 

The marijuana plant (Cannabis sativa) contains 

delta-9-tetrahydrocannabinol (THC) that can disrupt 

these processes, if administered repeatedly and/or in 

high enough concentrations. 

Carcinogen: Any substance that causes cancer. 

Cerebellum: A large structure located in the back 

of the brain that helps control the coordination of 

movement by making connections to other parts of 

the CNS (pons, medulla, spinal cord, and thalamus). 

It also may be involved in aspects of motor learning.

Cerebral Cortex: The outermost layer of the 

cerebral hemispheres of the brain. It is largely 

responsible for conscious experience, including 

perception, emotion, thought, and planning.

Cognitive-Behavioral Therapy (CBT): A form of 

psychotherapy that teaches people strategies to 

identify and correct problematic behaviors in order 

to enhance self-control, stop drug use, and address 

a range of other problems that often co-occur with 

them. 

Contingency Management (CM): A therapeutic 

management approach based on frequent 

monitoring of the target behavior and the provision 

(or removal) of tangible, positive rewards when the 

target behavior occurs (or does not). CM techniques 

have shown to be effective for keeping people in 

treatment and promoting abstinence. 

Dopamine: A brain chemical, classified as a 

neurotransmitter, found in regions of the brain 

that regulate movement, emotion, motivation, and 

pleasure. 

Hippocampus: A seahorse-shaped structure located 

within the brain that is considered an important part 

of the limbic system. One of the most studied areas 

of the brain, the hippocampus plays key roles in 

learning, memory, and emotion. 

Hydrocarbon: Any chemical compound containing 

only hydrogen and carbon. 

Motivational Enhancement Therapy (MET): A 

systematic form of intervention designed to produce 

rapid, internally motivated change. MET does not 

attempt to treat the person, but rather mobilize their 

own internal resources for change and engagement 

in treatment.

Psychosis: A mental disorder (e.g., schizophrenia) 

characterized by delusional or disordered thinking 

detached from reality; symptoms often include 

hallucinations.

Schizophrenia: A psychotic disorder characterized 

by symptoms that fall into two categories: (1) 

positive symptoms, such as distortions in thoughts 

(delusions), perception (hallucinations), and 

language and thinking and (2) negative symptoms, 

such as flattened emotional responses and 

decreased goal-directed behavior. 

Schizophreniform Disorders: Similar to 

schizophrenia, but of shorter duration and possibly 

lesser severity. 

THC: Delta-9-tetrahydrocannabinol; the main active 

ingredient in marijuana, which acts on the brain to 

produce its effects. 

Ventral Striatum: An area of the brain that is part 

of the basal ganglia and becomes activated and 

flooded with dopamine in the presence of salient 

stimuli. The release of this chemical also occurs 

during physically rewarding activities such as eating, 

sex, and taking drugs, and is a key factor behind our 

desire to repeat these activities.

Withdrawal: Adverse symptoms that occur after 

chronic use of a drug is reduced or stopped.

10 NIDA Research Report Series
References

1 Substance Abuse and Mental Health Services 

Administration, Office of Applied Studies. Results 

from the 2010 National Survey on Drug Use and 

Health: Summary of National Findings. HHS Pub. 

No. (SMA) 11–4658, Rockville, MD: SAMHSA, 

2011.

2 Institute for Social Research. Monitoring the 

Future, 2011 (Study Results). Ann Arbor, MI: 

University of Michigan, 2012. Data retrieved 

7/24/2012 from http://www.monitoringthefuture.

org.

3 Timberlake, D.S. A comparison of drug use and 

dependence between blunt smokers and other 

cannabis users. Subst Use Misuse 44(3):401–415, 

2009.

4 Substance Abuse and Mental Health Services 

Administration. Office of Applied Studies. Drug 

Abuse Warning Network, 2009: National Estimates 

of Drug-Related Emergency Department Visits. 

DHHS Publication No. (SMA) 11-4659, DAWN 

Series D-35. Rockville, MD, 2011.

5 Mehmedic, Z.; Chandra, S.; Slade, D.; Denham, 

H.; Foster, S.; Patel, A.; Ross, S.; Khan, I.; and 

ElSohly, M. Potency trends of Δ9-THC and other 

cannabinoids in confiscated cannabis preparations 

from 1993 to 2008. J Forensic Sci 55(5):1209–

1217, 2010.

6 Polen, M.R.; Sidney, S.; Tekawa, I.S.; Sadler, M.; 

and Friedman, G.D. Health care use by frequent 

marijuana smokers who do not smoke tobacco. 

West J Med 158(6):596–601, 1993.

7 Caspi, A.; Moffitt, T.E.; Cannon, M.; McClay, J.; 

Murray, R.; Harrington, H.; Taylor, A.; Arseneault, 

L.; Williams, B.; Braithwaite, A.; Poulton, R.; 

and Craig, I.W. Moderation of the effect of 

adolescent-onset cannabis use on adult psychosis 

by a functional polymorphism in the catechol-Omethyltransferase gene: Longitudinal evidence of 

a gene X environment interaction. Biol Psychiatry 

57(10):1117–1127, 2005.

8 Hashibe, M.; Morgenstern, H.; Cui, Y.; Tashkin, 

D.P.; Zhang, Z.F.; Cozen, W.; Mack, T.M.; and 

Greenland, S. Marijuana use and the risk of 

lung and upper aerodigestive tract cancers: 

Results of a population-based case-control 

study. Cancer Epidemiol Biomarkers Prev 

15(10):1829–1834, 2006.

9 Hall, W., and Degenhardt, L. Adverse health 

effects of non-medical cannabis use. Lancet 

374(9698):1383–1391, 2009.

10 Substance Abuse and Mental Health 

Services Administration. Office of Applied 

Studies. Treatment Episode Data Set (TEDS) 

Highlights—2009: National Admissions to 

Substance Abuse Treatment Services. Office 

of Applied Studies, DASIS Series: S-45, DHHS 

Publication No. SMA 09–4360, Rockville, MD, 

2008.

11 Schweinsburg, A.D.; Brown, S.A.; and Tapert, 

S.F. The influence of marijuana use on 

neurocognitive functioning in adolescents. Curr 

Drug Abuse Rev 1(1):99–111, 2008. 

12 Fergusson, D.M., and Boden, J.M. Cannabis 

use and later life outcomes. Addiction 

103(6):969–976; discussion 977–968, 2008.

13 Macleod, J.; Oakes, R.; Copello, A.; Crome, 

I.; Egger, M.; Hickman, M.; Oppenkowski, T.; 

Stokes-Lampard, H.; and Davey Smith, G. 

Psychological and social sequelae of cannabis 

and other illicit drug use by young people: 

A systematic review of longitudinal, general 

population studies. Lancet 363(9421):1579–

1588, 2004.

14 O’Malley, P.M., and Johnston, L.D. Drugs and 

driving by American high school seniors, 2001–

2006. J Stud Alcohol Drugs 68(6):834–842, 

2007.

15 Richer, I., and Bergeron, J. Driving under the 

influence of cannabis: Links with dangerous 

driving, psychological predictors, and accident 

involvement. Accid Anal Prev 41(2):299–307, 

2009.

Continued on page 12

NIDA Research Report Series 11
16 Trezza, V.; Campolongo, P.; Cassano, 

T.; Macheda, T.; Dipasquale, P.; Carratu, 

M.R.;Gaetani, S.; Cuomo, V. Effects of perinatal 

exposure to delta-9-tetrahydrocannabinol on 

the emotional reactivity of the offspring: A 

longitudinal behavioral study in Wistar rats.

Psychopharmacology (Berl) 198(4):529–537, 

2008.

17 Schempf, A.H., and Strobino, D.M. Illicit drug 

use and adverse birth outcomes: Is it drugs or 

context? J Urban Health 85(6):858–873, 2008.

18 Gouzoulis-Mayfrank, E. Dual diagnosis 

psychosis and substance use disorders: 

Theoretical foundations and treatment. Z Kinder 

Jugendpsychiatr Psychother 36(4):245–253, 

2008.

To learn more about marijuana

and other drugs of abuse, or to 

order materials on these topics free 

of charge in English or Spanish, 

visit the NIDA Web site at www.

drugabuse.gov or contact the 

DrugPubs Research Dissemination 

Center at 877-NIDA-NIH 

(877-643-2644; TTY/TDD: 

240-645-0228).

What’s on the NIDA Web Site

• Information on Drugs of 

Abuse and Related Health 

Consequences

• NIDA Publications, 

News, and Events

• Resources for Health 

Care Professionals

• Funding Information

• International Activities

NIDA Web Sites

NIDA Home Page:

http://www.drugabuse.gov

NIDA Drug Facts:

http://www.drugabuse.gov/

publications/term/160/DrugFacts

Easy-to-Read Drug Facts:

http://easyread.drugabuse.gov

NIDA/SAMHSA Blending Initiative: 

http://www.drugabuse.gov/blendinginitiative

For Physician Information 

www.drugabuse.gov/nidamed

Other Web Sites

Information on marijuana abuse is 

also available through the following 

Web site:

• Substance Abuse and Mental 

Health Services Administration 

Health Information Network: 

www.samhsa.gov/shin

NIH Publication Number 12-3859 

Printed October 2002, Reprinted March 2003, 

Printed July 2005, Revised September 2010, Revised July 2012.

Feel free to reprint this publication.

Where Can I Get More Scientific 

Information on Marijuana Abuse? 

References

Continued from page 11