By Martha McLaughlin

The human brain is a marvelously complex organ with areas that specialize in different tasks. As brain science develops, researchers are beginning to more fully understand how substance abuse and addiction affect it. These changes can be observed in many regions of the brain, including the prefrontal cortex, the nucleus accumbens and the anterior cingulate cortex (ACC).

Let’s take a closer look at each of those areas below.

Drugs and Dopamine

The prefrontal cortex — involved with planning and carrying out activities — works together with the nucleus accumbens — a cluster of nerve cells located under the cerebral cortex — to turn substance use into abuse and addiction.

When people experience pleasure, the neurotransmitter dopamine is released in the nucleus accumbens. All drugs of abuse raise dopamine, and the risk of addiction is tied to the speed, intensity and reliability of the surge. Drugs may release up to 10 times more dopamine than natural rewards do.

The nucleus accumbens and the prefrontal cortex ensure that enjoying an activity is linked with wanting to repeat it. The prefrontal cortex motivates action to continue doing whatever caused the dopamine levels to rise.

Because dopamine levels produced by drugs of abuse are so much higher than what the body considers normal, it compensates in an attempt to restore balance. The body may adapt in a number of ways. It may reduce the number of dopamine receptor cells in the brain or increase the number of dopamine transporters, which clear the neurotransmitter from the gaps between nerve cells.

These adaptations cause drug tolerance — the need to increase dosage in order to feel the effects a lower dose once produced. They also explain anhedonia, the inability to feel pleasure from normal activities, which is a common symptom in addicted individuals and those in early recovery.

Conflicts and Decisions

Another way the body responds to addiction is to shrink and weaken the ACC, the part of the brain that links pain and conflict with thoughts and behaviors. Dr. Nicole Gravagna notes that healthy brains feel pain, evaluate risks and danger, and make decisions based on the information received. By influencing the ACC, substance abuse makes it more difficult for people to handle conflict. Gravagna states that people become “conflict-stupid,” and their ability to get past the pain of opposition is impaired.1

The ACC evaluates rewards and punishments and works with other brain regions to use that information to guide decisions. A study reported by Science Daily looked at the brain activity of adolescent boys with conduct and substance use disorders. They were found to have significantly less activity in the ACC and other key areas while engaged in decision-making tasks. When playing a game, they responded less than normal to wins and more than normal to losses.2

The effect of drugs and alcohol on the ACC can become part of a self-perpetuating cycle, where conflict and pain are felt more deeply, and people turn to substances to numb the feelings. ACC-related impairments may also make it difficult for people to clearly evaluate the risks of their substance abuse.

Age and Gender Differences

Because their brains are still developing, brain changes are often more pronounced and long-lasting in teens than in adults. The part of the brain most involved in overriding impulses and making rational decisions isn’t fully developed until the mid-20s. Unfortunately, drug use can interfere with that process and slow development even further.

There are also gender differences in how addiction changes the brain. Researchers at Boston University studied individuals who had once been heavy drinkers and found that the length of time that alcohol had been abused corresponded to smaller areas of white matter. In men, the corpus callosum region of the brain was most affected, but in women the losses were seen in the cortex.3

Healing and Recovery

Some of the effects of drug and alcohol on the brain, such as the death of neurons, appear to be permanent. But in many ways, the brain can change itself, and a significant degree of healing is possible. Addiction-related changes in the ACC, for example, are often seen to reverse after people recover.

It’s not easy to predict how long it will take the brain to heal. Some changes occur quickly, but others may take months or even years. The Boston University study found that restoration of white matter after the cessation of drinking appears to occur more quickly in women than in men.3

The fact that brain healing takes time helps explain the relapse risk for people in recovery from addiction. Despite the best of intentions, people often have trouble maintaining sobriety without the support of others. A comprehensive addiction treatment program can help patients understand the healing process and assemble a toolbox of skills to help them rebuild their lives while their bodies work on rebuilding their brains.


1 Gravagna, Nicole. “How Does Addiction Physically Change The Brain?Forbes, August 22, 2017.

2Could brain abnormalities cause antisocial behavior and drug abuse in boys?Science Daily, September 27, 2010.

3 Seligson, Susan. “Why Alcoholics’ Gender Matters.” BU Today, November 21, 2013.