A Research Update from the National Institute on Drug Abuse — January 2007
Is drug addiction a disease?
Yes. Addiction is a chronic, relapsing disease that
affects the brain and causes compulsive drug seeking
and use despite harmful consequences.
- How is addiction a disease? Addiction is
considered a brain disease because drugs
change the brain– in structure and in function.
It's true that for most people, the initial decision
to take drugs is voluntary. Over time, however,
drug abuse can cause changes to the brain that
erode a person's self control and ability to make
sound decisions, while sending intense
impulses to take drugs.
- What is its course? Drug addiction is a
chronic, relapsing disease – like diabetes,
asthma, or heart disease – and it can be
managed successfully. Treatment helps people
to counteract addiction's powerful disruptive
effects and regain control of their lives. And just
as with other chronic diseases, relapses are not uncommon. But relapse does not signal failure– rather, it
indicates that treatment should be reinstated or adjusted to help the addict fully recover.
Why do some people become addicted, while 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 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 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– with adolescents experiencing a double threat. Although taking drugs
at any age can lead to addiction, the earlier 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.
How do drugs work in the brain?
Drugs tap into the brain's communication system and disrupt the way nerve cells normally send, receive, and
process information. Drugs work in the brain by:
- Imitating natural neurotransmitters (chemical messengers in the brain). Because of the similarity
in chemical structure between drugs and neurotransmitters naturally produced by the brain, some
drugs, such as marijuana and heroin, are able to "fool" the brain's receptors and activate nerve cells to
send abnormal messages via the network.
- Overstimulating the reward system by flooding the circuit with dopamine. Dopamine is a
neurotransmitter present in regions of the brain that regulate movement, emotion, motivation, and
feelings of pleasure. And nearly all drugs of abuse, directly or indirectly, activate this system. Some
drugs, particularly stimulants like methamphetamine and cocaine, cause nerve cells to release
abnormally large amounts of natural neurotransmitters or prevent their normal recycling, which is
needed to shut off the signal between neurons.
What happens to your brain if you keep taking drugs?
- The brain adapts. In response to the overwhelming surges in dopamine, the brain adjusts by
decreasing the number of dopamine receptors available– thus diminishing the function of the reward
circuit. Drug addicts are compelled to abuse drugs to bring their dopamine function back up to normal,
requiring ever larger amounts to achieve the initial dopamine high– an effect known as tolerance.
- Changes in neurotransmitters other than dopamine. Long-term abuse causes changes in other
brain chemical systems, including glutamate, 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 cause impairment in cognitive function.
- Drug abuse can trigger nonconscious memory systems. Conditioning is one example of this type
of learning, whereby environmental cues, such as certain people or places, become associated with
the drug experience and can trigger uncontrollable cravings if the individual is exposed to these cues,
even without the drug itself being available.
- Addiction. 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. These changes
are likely what drive an abuser to seek out and take drugs compulsively despite adverse
consequences.
Can addiction be treated successfully?
Yes. Research shows that combining addiction treatment medications, where available, with behavioral therapy is
the best way to ensure success for most patients. Treatment approaches that are tailored to address each
patient's drug abuse patterns and co-occurring medical, psychiatric, and social problems can lead to sustained
recovery and a life without drug abuse.
Addiction need not be a life sentence.
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