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Understanding Drug Abuse and Addiction

Many people do not understand why
individuals become addicted to drugs or
how drugs change the brain to foster
compulsive drug abuse. They mistakenly
view drug abuse and addiction as strictly a social problem and may characterize those who take drugs as morally
weak. One very common belief is that
drug abusers should be able to just stop
taking drugs if they are only willing to
change their behavior. What people
often underestimate is the complexity of
drug addiction—that it is a disease that
impacts the brain and because of that,
stopping drug abuse is not simply a
matter of willpower. Through scientific
advances we now know much more
about how exactly drugs work in the
brain, and we also know that drug
addiction can be successfully treated to
help people stop abusing drugs and
resume their productive lives.
Drug abuse and addiction are a major
burden to society. Estimates of the total
overall costs of substance abuse in the
United States—including health- and
crime-related costs as well as losses
in productivity—exceed half a trillion
dollars annually. This includes approximately $181 billion for illicit drugs,1
$168 billion for tobacco,2 and $185
billion for alcohol.3 Staggering as these
numbers are, however, they do not fully
describe the breadth of deleterious public health—and safety—implications,
which include family disintegration, loss
of employment, failure in school, domestic
violence, child abuse, and other crimes.
What is drug addiction?
Addiction is a chronic, often relapsing
brain disease that causes compulsive
drug seeking and use despite harmful
consequences to the individual who is
addicted and to those around them.
Drug addiction is a brain disease
because the abuse of drugs leads to
changes in the structure and function of
the brain. Although it is true that for
most people the initial decision to take
drugs is voluntary, over time the changes
in the brain caused by repeated drug
abuse can affect a person’s self control
and ability to make sound decisions,
and at the same time send intense
impulses to take drugs.
It is because of these changes in the
brain that it is so challenging for a person who is addicted to stop abusing
drugs. Fortunately, there are treatments
that help people to counteract addiction’s powerful disruptive effects and
Understanding Drug Abuse
and Addiction
June 2008 Page 2 of 4
regain control. Research shows that combining addiction treatment medications,
if available, with behavioral therapy is
the best way to ensure success for most
patients. Treatment approaches that are
tailored to each patient’s drug abuse
patterns and any co-occurring medical,
psychiatric, and social problems can
lead to sustained recovery and a life
without drug abuse.
Similar to other chronic, relapsing diseases, such as diabetes, asthma, or
heart disease, drug addiction can be
managed successfully. And, as with
other chronic diseases, it is not uncommon for a person to relapse and begin
abusing drugs again. Relapse, however,
does not signal failure—rather, it indicates that treatment should be reinstated,
adjusted, or that alternate treatment is
needed to help the individual regain
control and recover.
What happens to your brain
when you take drugs?
Drugs are chemicals that tap into the
brain’s communication system and disrupt the way nerve cells normally send,
receive, and process information. There
are at least two ways that drugs are
able to do this: (1) by imitating the
brain’s natural chemical messengers,
and/or (2) by overstimulating the
“reward circuit” of the brain.
Some drugs, such as marijuana and
heroin, have a similar structure to chemical messengers, called neurotransmitters,
which are naturally produced by the
brain. Because of this similarity, these
drugs are able to “fool” the brain’s
receptors and activate nerve cells to
send abnormal messages.
Other drugs, such as cocaine or
methamphetamine, can cause the nerve
cells to release abnormally large
amounts of natural neurotransmitters, or
prevent the normal recycling of these
brain chemicals, which is needed to shut
off the signal between neurons. This disruption produces a greatly amplified
message that ultimately disrupts normal
communication patterns.
Nearly all drugs, directly or indirectly,
target the brain’s reward system by
flooding the circuit with dopamine.
Dopamine is a neurotransmitter present
in regions of the brain that control movement, emotion, motivation, and feelings
of pleasure. The overstimulation of this
system, which normally responds to
natural behaviors that are linked to survival (eating, spending time with loved
ones, etc.), produces euphoric effects in
response to the drugs. This reaction sets
in motion a pattern that “teaches” people
to repeat the behavior of abusing drugs.
As a person continues to abuse drugs,
the brain adapts to the overwhelming
surges in dopamine by producing less
dopamine or by reducing the number
of dopamine receptors in the reward circuit. As a result, dopamine’s impact on
the reward circuit is lessened, reducing
the abuser’s ability to enjoy the drugs
and the things that previously brought
pleasure. This decrease compels those
June 2008 Page 3 of 4
addicted to drugs to keep abusing
drugs in order to attempt to bring their
dopamine function back to normal.
And, they may now require larger
amounts of the drug than they first did
to achieve the dopamine high—an
effect known as tolerance.
Long-term abuse causes changes in other
brain chemical systems and circuits as
well. Glutamate is a neurotransmitter
that influences the reward circuit and the
ability to learn. When the optimal concentration of glutamate is altered by
drug abuse, the brain attempts to compensate, which can impair cognitive
function. Drugs of abuse facilitate nonconscious (conditioned) learning, which
leads the user to experience uncontrollable cravings when they see a place or
person they associate with the drug
experience, even when the drug itself is
not available. Brain imaging studies of
drug-addicted individuals show changes
in areas of the brain that are critical to
judgment, decisionmaking, learning and
memory, and behavior control. Together,
these changes can drive an abuser to
seek out and take drugs compulsively
despite adverse consequences—in other
words, to become addicted to drugs.
Why do some people become
addicted and others do not?
No single factor can predict whether or
not a person will become addicted to
drugs. Risk for addiction is influenced by
a person’s biology, social environment,
and age or stage of development. The
more risk factors an individual has, the
greater the chance that taking drugs can
lead to addiction. For example:
• Biology. The genes that people are
born with––in combination with environmental influences––account for
about half of their addiction vulnerability. Additionally, gender, ethnicity,
and the presence of other mental
disorders may influence risk for drug
abuse and addiction.
• Environment. A person’s environment includes many different influences––from family and friends to
socioeconomic status and quality of
life in general. Factors such as peer
pressure, physical and sexual abuse,
stress, and parental involvement
can greatly influence the course of
drug abuse and addiction in a
person’s life.
• Development. Genetic and environmental factors interact with critical
developmental stages in a person’s
life to affect addiction vulnerability,
and adolescents experience a double
challenge. Although taking drugs at
any age can lead to addiction, the
earlier that drug use begins, the
more likely it is to progress to more
serious abuse. And because adolescents’ brains are still developing in
the areas that govern decisionmaking, judgment, and self-control, they
are especially prone to risk-taking
behaviors, including trying drugs
of abuse.
June 2008 Page 4 of 4
Prevention is the key
Drug addiction is a preventable disease.
Results from NIDA-funded research have
shown that prevention programs that
involve families, schools, communities,
and the media are effective in reducing
drug abuse. Although many events and
cultural factors affect drug abuse trends,
when youths perceive drug abuse as
harmful, they reduce their drug taking. It
is necessary, therefore, to help youth
and the general public to understand the
risks of drug abuse, and for teachers,
parents, and healthcare professionals to
keep sending the message that drug
addiction can be prevented if a person
never abuses drugs.
For more information
For information on understanding drug
abuse and addiction, please see our
booklet, Drugs, Brains, and Behavior –
The Science of Addiction, at www.
For more information on prevention,
please visit
For more information on treatment,
please visit
drugpages/treatment.html. To find a
publicly funded treatment center in your
State, please call 1-800-662-HELP or
1 Office of National Drug Control Policy. The Economic Costs of Drug Abuse in the United States: 1992-2002.
Washington, DC: Executive Office of the President (Publication No. 207303), 2004.
2 Centers for Disease Control and Prevention. Annual Smoking–Attributable Mortality, Years of Potential Life Lost, and
Productivity Losses — United States, 1997–2001. Morbidity and Mortality Weekly Report 54(25):625–628, July 1,
3 Harwood, H. Updating Estimates of the Economic Costs of Alcohol Abuse in the United States: Estimates, Update
Methods, and Data Report. Prepared by the Lewin Group for the National Institute on Alcohol Abuse and Alcoholism,

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