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What is Addiction?

What is Addiction?

Addiction Basics

Addiction—the severe form of a substance use disorder—is a chronic, relapsing brain disease characterized by compulsive substance-seeking and use despite harmful consequences.1

It is considered a brain disease because in some people substance use changes how the brain functions. These changes make it progressively more difficult to stop the unhealthy behaviors that are common among people with an active SUD.

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Addiction and the Brain

The brain is the most complex organ in the human body. It regulates basic functions, enables us to interpret and respond to experiences, and generates our thoughts, emotions, and behaviors.


Alcohol and drug use can affect important areas of the brain that control motivation, impulse control, reaction to stress, memory, and decision-making, and can eventually lead to the compulsive substance-seeking and use that is central to the experience of substance use disorders (SUDs).


In the early 1990s, scientists began to understand how repeated substance use affects the brain. Brain scans showed that, as is the case with other brain disorders, SUD affects tissue function in two main parts of the brain: the limbic system and the cortex.

How does a substance use disorder develop?

While the initial decision to use alcohol or drugs tends to be voluntary, no one chooses to become addicted. Many people start using substances to feel good, to feel better, to do better, or out of curiosity (because “everyone else is doing it”). However, as a SUD develops and progresses, it affects brain function, and a person’s ability to control their use diminishes. What was once a decision to use turns into a compulsion. This is why engaging with treatment as soon as possible is so important.

Stressful life events such as the death of a loved one, severe illness, exposure to violence or trauma, and extreme stress can prompt people to use substances in risky ways, often as an attempt to cope, which can spiral into the development of a SUD.

SUDs can develop at any age, but people who start using substances as adolescents have a much higher risk of developing a SUD later in life.


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