What Happens Inside an Addicted Brain?

What Happens Inside an Addicted Brain?

In this day and age, it is widely recognized and accepted that substance dependence is a brain disease. Unfortunately, addiction and alcoholism still carry a stigma for many people. However, the medical world and society as a whole are coming to understand that these conditions are actually mental and physical disorders that require evidence-based treatment. This is largely because of research that has given us a better picture of the addicted brain, and what happens to the brain chemistry of an addicted or alcoholic individual. These new insights have helped us to better understand and treat the disease of addiction.

Serotonin and Dopamine in the Addicted Brain

The brain is the most complex and least understood organ in the human body. Decades of focused research have allowed for scientists and medical professionals to better understand how certain brain processes work. We know that the brain sends signals through chemicals, or neurotransmitters, to different receptors in the brain. Everything we think, feel, and do is the result of the brain sending signals throughout its neurons and receptors. Two of the chemical signals our brains use are serotonin and dopamine.

Serotonin and Dopamine in the Addicted Brain


Serotonin is the chemical responsible for feelings of content and happiness. It regulates mood and helps with sleep and digestion. People who suffer from depression and anxiety tend to have low levels of serotonin. Serotonin deficiency can cause mood disorders. These can prompt individuals to seek destructive coping mechanisms, including substance abuse.


This is the brain’s reward system or the pleasure chemical. Dopamine is responsible for joy and satisfaction. Dopamine also regulates memory, movement, sleep, pain processing, and behavior. Low levels of dopamine can lead to depression and fatigue, while high levels can prompt mania and euphoria. This is the function of the brain that leads people to seek out pleasurable activities. When the individual does something that produces dopamine, the brain processes that action as “rewarding” or useful

In an addicted brain, substances hijack chemical signals, causing the behaviors associated with active addiction.

A Hijacked Brain

The reason that drugs or alcohol become paramount to all other priorities, motivations, and activities in an addicted person is because substances essentially hijack and control the brain’s reward system. In order to survive and evolve, the human brain developed a reward system. Functions that are necessary for survival in the world of natural selection and evolution (like eating or mating) produce positive chemicals to encourage us to repeat those behaviors. This is how human beings survived throughout history. Our brains created a system to encourage us to seek out behaviors that benefit the survival of the species. Substances bypass that system by producing reward chemicals that flood the brain and body with a good feeling. This feeling tricks our brains into believing that the substance is good for us and necessary for survival.

Neurotransmitters and Addiction

The overproduction of dopamine and serotonin caused by using a drug teach our brains that we actually need that substance for survival, causing us to seek out more. Addiction occurs because, over time, our brains become dependent upon a substance to produce dopamine and serotonin. The addicted brain has lost the ability to produce these chemicals on its own, through normal activities that humans need in order to function. And without these chemical signals that regulate happiness, pleasure, mood, and bodily function, the brain actually believes that the body is in danger or even dying. This is what causes withdrawal: without the chemicals that regulate all of these aspects of life, the brain sends distress signals throughout the body that causes cravings and compulsive use.

How it Works: A Breakdown

People with low levels of dopamine or serotonin may suffer from painful emotional feelings or an inability to function. For some of these individuals, using a substance may provide relief because it causes the brain to produce these chemicals. That individual may become hooked on a substance because, for a short period of time, it works. However, as the brain loses the ability to produce these chemicals on its own, the individual becomes addicted to the substance and experiences the emotional and behavioral consequences of drug or alcohol dependence. Someone with a natural imbalance that causes overproduction of serotonin or dopamine, in contrast, may have poor impulse control and begin using drugs or alcohol as a result. In these individuals, the same thing can happen with prolonged use: brain dependence on drugs or alcohol, and physical and emotional addiction.

Brain Chemistry and Addiction

Brain chemistry is complex and individual, but generally, within an addicted brain the process follows a similar path:

  1. Individual experiments with drugs (this can happen due to a variety of internal and external factors, but dopamine or serotonin deficiency or surplus can contribute).
  2. The brain sends reward signals, like dopamine and serotonin, throughout its neurons and receptors. This produces pleasurable feelings that the brain mistakes for evolutionarily beneficial activities, like eating or sleep.
  3. As the brain is flooded with dopamine and serotonin, it shuts down its own natural production of these chemicals. When the substance is removed, the brain experiences distress.
  4. Low dopamine and serotonin cause the addicted brain to crave what produces these chemicals: the drugs or alcohol.
  5. The individual’s brain becomes dependent on substances, and experiences withdrawal without them, leading to physical and/or psychological addiction.

What’s the Solution?

Addiction is a brain disease, and the addicted brain requires evidence-based treatment in order to recover. Addicts and alcoholics need treatment in order to beat addiction because recovery requires an entire rewiring of the brain back to normal functioning. In order to properly treat addicts and alcoholics for their disease, a comprehensive understanding of what causes the brain to react to substances in the ways that it does is necessary. Fortunately, as we learn more about the addicted brain, the disease is becoming less stigmatized and addressed with the proper care required for patients to recover.

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