Neuroscience of Addiction: Simplified

What’s going on in the brain behind addiction?

Let’s explore the brain chemistry behind pleasure and addiction. While addiction is a complex condition that we still don’t know everything about, there are certain neuroscience concepts that I’ve summarized to help better explain what we do know about this mental illness.

What Is Addiction?

There are various definitions of addiction. The National Institute on Drug Abuse (NIDA) defines addiction as a chronic, relapsing brain disease that’s characterized by compulsive drug seeking and use despite harmful consequences. Brain changes caused by addiction can be long lasting and can lead to many harmful, often self-destructive, behaviors.

What Can You Become Addicted To?

When we think of addiction, we tend to think of drugs and alcohol. However, one can become addicted to anything that stimulates the brain’s dopamine reward pathway. Video games, shopping, sugar, thrill-seeking, and social media are just some potential sources of addiction. In the case of social media, the variable reward system associated with receiving “likes,” comments, and followers boosts dopamine release, fostering feelings of pleasure and perpetuating a cycle of dependence. While many things have the potential to become addicting, how do we determine when dependence is a problem?

DSM-5 Diagnosis

In order to officially diagnose a substance use disorder, clinicians use the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). The DSM-5 was created by hundreds of international experts on behavioral health with the purpose to improve diagnoses, treatment, and research. The essential feature of a substance use disorder is a group of cognitive, behavioral, and physiological symptoms that show a person continues using a substance despite significant substance-related problems.

Changes in Brain Chemistry

Alcohol and drugs produce their psychoactive effects by altering brain chemistry. More specifically, neurotransmitters, or chemical messengers in the brain, responsible for daily functions (e.g., learning, memory, appetite, pleasure, pain) are altered by substance use. A key neurotransmitter in the process of pleasure and addiction is dopamine.

Dopamine and Reward

In addition to its primary role in pleasure and addiction, dopamine is also involved in processes like learning, cognition, memory, and movement. Most of your dopamine is generated deep in the midbrain and released in three pathways across the brain as shown below.

It’s natural for people to seek out experiences that result in pleasure by stimulating the dopamine reward pathway. For example, natural processes that stimulate the dopamine reward pathway include exercising, eating, meditating, and having sex.

Natural Reward vs. Substance-Induced Reward

When people seek out experiences that feel good, these experiences boost dopamine. When people use drugs, dopamine transmission can be 3-5x greater than natural sources of pleasure. As you can imagine, this is not sustainable.

With consistent drug use, the brain becomes accustomed to experiencing pleasure with significantly greater transmissions of dopamine. This is not sustainable.
Photo by Andrii Vodolazhskyi on Shutterstock

Down-Regulation of Dopamine

Continual activation of the dopamine pathway reduces the availability of dopamine in the brain. This reduction, or down-regulation, in dopamine availability has a blunting effect on the natural reward circuit. This partly explains why those who abuse substances may find it difficult to enjoy natural pleasures that they previously did. Something that once naturally caused pleasure no longer does as the reward circuit has been desensitized.

The down-regulation of dopamine: Continual activation of the dopamine pathway results in a dampening effect on one’s ability to experience pleasure due to lack of available dopamine.
Photo by the New York State Office of Alcoholism and Substance Abuse Services

Is Sugar Addiction Real?

As mentioned earlier, one can become addicted to any substance or activity that stimulates the brain’s dopamine pathway. Sugar, for example, can be a highly addictive substance that can change one’s brain chemistry. Neuroscientists have shown that sugar leads to dopamine release just as drugs do (e.g., cocaine, heroin). Also, sugar can lead to changes in dopamine receptors, increasing tolerance and requiring more sugar over time for the same effects.

Since the dopamine pathway is involved with both sugar consumption and drug use, research has shown that those addicted to drugs can have increased cravings for sugar when they’re in early sobriety. This effect, known as cross-tolerance, illustrates that addiction to one substance makes it easier to become addicted to another substance that may use the same brain mechanisms. For example, marijuana is often referred to as a “gateway drug” as it may introduce the dopamine pathway to seek further experiences of drug use.

Self-Medicating Mental Illness

As discussed in the neuroscience of depression and anxiety, mental illness can be caused by an imbalance in the brain’s neurotransmitter activity. Mental illness and substance abuse are often comorbid and bidirectionally influence each other. Feelings of depression, for example, can lead to self-medication with substance use as it may the depression by stimulating dopamine release. External dependence on regulating one’s mood can quickly develop into a vicious cycle that leads to dopamine depletion and dependence.

“Times like these” are often ones of intense emotional distress as it’s easier to numb the pain than fully experience it.
Photo by Clipart.Email

Addiction as a Brain Disease

Substance abuse can cause lasting changes to brain chemistry, especially the dopamine reward pathway. Limited availability of dopamine in certain areas of the brain may desensitize the reward circuit to natural sources of pleasure. People may choose continued substance use to compensate for the deficit in dopamine availability, thus perpetuating the cycle of addiction.

Reversible Changes

It’s possible for one’s brain to return to its baseline availability of dopamine after substance abuse. Research has shown that extended periods of sobriety, lasting at least twelve months, may be required for partial recovery of normal dopamine function. The time it takes for one’s dopamine functioning to revert to its normal state may be longer than some people are able to abstain from substance abuse.

However, some people who receive treatment may not be able to return to normal dopamine pathway functioning depending on one’s history of substance abuse. As it can be incredibly challenging to retrain the brain’s cravings for substance-induced pleasure, and avoid triggers for substance use, rates of relapse are greatest in early sobriety.

Withdrawals: a Price of Addiction

Have you ever experienced irritability, fatigue, or cravings after you stopped eating sugar, drinking caffeine, or smoking marijuana? Most substance use results in withdrawal symptoms that can range from mild headaches to severe flu-like symptoms — depending on the substance in question and how chronic your dependence was. You feel irritable, sick, and fatigued because your brain is struggling to cope without the substance it became dependent on to feel normal. Also, contrary to popular belief, chronic substance users don’t solely continue using a drug to get “high,” but rather to prevent withdrawal symptoms that can interfere with daily life.

In addition to physical symptoms, withdrawals can entail changes in mood, such as periods of depression or anxiety. These mood fluctuations can lead to relapse in an effort to self-medicate.

Medication-Assisted Treatment

Medication-assisted treatment, or “MAT,” is the use of medications in combination with counseling and behavioral therapies to treat substance use disorders. It can allow people to live satisfying, functional lives by relieving withdrawal symptoms and psychological cravings. For example, in the case of opioid addiction, methadone, is an approved MAT. Methadone “tricks” the brain into thinking it’s still getting opiates that it’s become dependent on. When used as prescribed, methadone mitigates withdrawal symptoms and does not cause one to feel “high.”  People may be on methadone for weeks, months, years, or a lifetime. When they wean from methadone depends on factors such as their biology, environmental stability, and psychological readiness to cope with potential cravings and triggers for drug use. For more on opioid dependence and narratives on substance abuse, visit my series on Untold Stories of Addiction.


Addiction is a chronic, relapsing brain disease that’s characterized by compulsive drug seeking and use despite harmful consequences. Brain changes caused by addiction, such as dopamine depletion, can be long lasting and can lead to many harmful, often self-destructive, behaviors. Also, addiction goes far beyond alcohol and drugs as humans can become dependent on anything that stimulates the brain’s dopamine reward pathway. Video games, shopping, sugar, thrill-seeking, and social media are just some potential sources of addiction. Understanding the process of addiction is critical for recovery. While cravings, withdrawal symptoms, and self-medication can pose barriers, recovery is possible and there is hope.

Is there something you’ve become dependent on? Do you experience cravings and compulsive behaviors? These are questions we must all periodically ask ourselves, especially in a society that normalizes and profits from addiction.

Addiction Treatment Resources

If you or a loved one is struggling with addiction of any kind, please know that there is treatment available. Utilizing SAMHSA’s (the Substance Abuse and Mental Health Services Administration) website or helpline is a great place to start for more information.

SAMHSA’s National Helpline, 1-800-662-HELP (4357): The National Helpline is a free, confidential, 24/7, 365-day-a-year treatment referral and information service (in English and Spanish) for individuals and families facing mental and/or substance use disorders.

Thank You

I’d like to express a huge thanks to the professor of my Addictions course in graduate school, Dr. Eric Devine. The knowledge gained from his class was an impetus for my work as a clinician in the field of addiction. To my readers, thank you for being a part of my journey as a mental health counselor.

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