The high. The withdrawals. The bad decisions. These are the effects that drugs have on the brain that drive addiction. But what actually causes these experiences on a chemical level?

Different substances affect the brain in different ways, but they all tie back to a little chemical called dopamine. Here’s how it works:

The Science of Drug Abuse and Addiction

To understand how addiction forms, you first have you understand the effects of drugs on the brain. There are three main categories of drugs that interact with the dopamine system:

  • Stimulants like cocaine and ecstasy directly affect dopamine transmitters. Dopamine is a chemical signal that relates to our desire for pleasurable activities. The stimulants increase dopamine levels, resulting in a euphoric high.
  • Depressants like alcohol affect the GABA system. Unlike stimulants, alcohol does not affect the dopamine system directly. Instead of increasing dopamine throughout the brain, it only leads to an increase in the reward pathway. Depressants decrease activity in the central nervous system, making the user feel calm and relaxed.
  • Opioids operate by blocking pain receptors. The substance actually occurs normally in the body, but not at the levels that occur when taking it as a drug. Opioids work similarly to stimulants in that they flood the brain with dopamine, creating a high.

When using any of these drugs, the body adjusts to the increased amounts of dopamine. To try to regulate itself, it reduces the amount of dopamine it releases. This can even mean shutting down the number of dopamine receptors so that the brain can’t register a high as effectively.

Of course, the result of this is drug tolerance. A user will find they need to take more and more of a substance to reach the same high. And because their normal dopamine levels are reduced, they’ll often feel lifeless and depressed without the drug. At this point, the individual is dependent on the drug.

Dependence vs. Addiction

So you know how drug dependence is formed. But is it the same as addiction?

Actually, while they often overlap, they are not quite the same. Drug dependence is a physical condition. The user needs the drug, and without it, he or she will experience withdrawal symptoms. You can build a dependence on many drugs, even those that are completely legal such as caffeine.

Addiction, however, takes dependence a step further. According to the American Society of Addiction Medication, addiction is defined as “a primary, chronic disease of brain reward, motivation, memory and related circuitry.” Unlike dependence, addiction is characterized by “inability to consistently abstain, impairment in behavioral control, craving, diminished recognition of significant problems with one’s behaviors and interpersonal relationships, and a dysfunctional emotional response.”

In other words, addiction occurs when the user sees the negative impact of the drug on his or her life and compulsively uses it anyway.

Drug Addiction Is a Disease

It’s not a moral failing or a lack of willpower. Drug addiction is a disease that breaks down the individual’s ability to use self-control.

The first time someone uses, it’s usually a voluntary choice. But the drug can alter the brain’s functioning to the point where they make choices they never would normally.

Not only does drug addiction cause intense cravings, but it breaks down your ability to resist them. That’s why it’s so powerful.

What Parts of the Brain Are Affected by Drug Abuse?

According to, there are several key parts of the brain that are affected by drug abuse.


The brainstem controls many of the basic body functions that keep you going through the day, such as heart rate, breathing, blood pressure, and sleepiness. At the top of the brainstem is a set of nerve cells that are important to the dopamine system.

Cerebral cortex

The cerebral cortex is the largest part of the brain. It’s divided into four areas that each process different information from our senses. It is intimately tied to our ability to work through problems and make sound decisions.

Many addictive substances are actually toxic to the brain and can damage it after time. This only makes conquering addiction more difficult, as the user might have their decision-making ability impaired.

Limbic system

The limbic system is a collection of several different structures, including the amygdala, thalamus, hypothalamus, hippocampus, basal ganglia, and cingulate gyrus. Together, the limbic system is in charge of the brain’s reward systems. This normally means encouraging you to do healthy things like eating and procreating, but it’s also affected by drug use. And because the limbic system is also where our emotions are created and processed, many drugs have mood-altering effects.

Addiction Is Treatable

If you have an addiction, escaping it can feel impossible. But we’ve helped individuals across the nation overcome it.

At The Recovery Village®, we offer a full spectrum of care to help you beat drug addiction. That means we’ll be by your side from the moment you check into detox through the day you find freedom. Learn more about drug rehab and our treatment programs.


“Alcohol and Dopamine.” HAMS Network. The HAMS Harm Reduction Network, 2012. Web. 25 Jul 2016. <>.

“How do opioids work in the brain?” The National Alliance of Advocates for Buprenorphine Treatment. Web. 25 Jul 2016. <>.

“The Science of Drug Abuse and Addiction: The Basics.” National Institute on Drug Abuse. U.S. Department of Health and Human Services, Sep 2014. Web. 26 Jul 2016. <>.

“Definition of Addiction.” American Society of Addiction Medicine. American Society of Addiction Medicine, 19 Apr 2011. Web. 25 Jul 2016. <>.

“Drugs and the Brain.” National Institute on Drug Abuse. U.S. Department of Health and Human Services, Jul 2014. Web. 25 Jul 2016. <>.

Medical Disclaimer

The Recovery Village aims to improve the quality of life for people struggling with substance use or mental health disorder with fact-based content about the nature of behavioral health conditions, treatment options and their related outcomes. We publish material that is researched, cited, edited and reviewed by licensed medical professionals. The information we provide is not intended to be a substitute for professional medical advice, diagnosis or treatment. It should not be used in place of the advice of your physician or other qualified healthcare providers.