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Recognizing the roots of addiction in the brain is key to understanding and addressing the substance abuse crisis affecting the United States. A recent study by scientists at Scripps Research may have located the source of alcohol cravings in the brain, further supporting addiction as a disease. But where does addiction occur in the brain exactly?

There are three major structures within the brain which are affected the most by drug and alcohol abuse: the prefrontal cortex, the basal ganglia, and the extended amygdala.

The Prefrontal Cortex and Addiction

The prefrontal cortex is responsible for conscious thought. This is where we think, problem solve, make plans and decisions. Most importantly, the prefrontal cortex is the self-control center of the brain. According to Dr. Nora Volkow, the director of NIH’s National Institute on Drug Abuse:

“Brain imaging studies of people addicted to drugs or alcohol show decreased activity in this frontal cortex. When the frontal cortex isn’t working properly, people can’t make the decision to stop taking the drug—even if they realize the price of taking that drug may be extremely high, and they might lose custody of their children or end up in jail. Nonetheless, they take it.”

In brains affected by addiction, the reduced impulse control leads to compulsive substance use in response to the stress and reward signals stemming from the extended amygdala and basal ganglia.

Stress, Substance Abuse, and the Extended Amygdala

The extended amygdala is responsible one’s stress response, including the feelings of anxiety, irritability, and unease which often accompany stressful situations. These emotions often correspond with withdrawal from drugs and alcohol, causing those suffering these symptoms to seek illicit substances as a means of relief. This combined with the reduced function of the prefrontal cortex creates a dangerous cycle of substance abuse which deepens the hold of addiction on the mind.

Continued substance abuse can heighten the sensitivity of the extended amygdala. Eventually drug and alcohol use is no longer about getting drunk or high, but rather avoiding withdrawal symptoms. As time continues, higher doses are necessary to maintain stasis, increasing the potential for serious health consequences. Despite an apparent increased tolerance, the risk of overdose is ever present.

How Addiction Affects the Basal Ganglia

The basal ganglia is known as the “reward circuit” of the brain. Responsible for positive motivations, the basal ganglia produces the pleasure responses to eating, socializing, and sex. This area of the brain controls procedural learning and the formation of habits as well as cognition and emotions, voluntary motor and eye movements.

Because the basal ganglia is responsible for biochemical responses that form habits, addiction heavily affects this area of the brain. Substance use floods the brain with dopamine causing the feelings of euphoria associated with drug use. Continued drug and alcohol use causes the brain to adapt to the presence of illicit substances in the body, reducing the brain’s sensitivity and making it more difficult to experience pleasure without using.

Understanding how addiction affects the brain is important to effective treatment. By recognizing the complex mental and physical aspects of substance abuse disorders, we are better able to develop comprehensive, integrated treatment programs that promote healing and long-term recovery.

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