The Science of Addiction

The Science of Addiction

Addiction is looked at differently today than it used to be. Although it still involves several factors, it all comes down to a known medical condition. People who become addicted to certain things actually have a treatable disease. Find out how science is changing the way we diagnose and treat people with addictions.

Defining Addiction

Neuroscientists define addiction in medical terms as a chronic, relapsing brain disease. Addiction is considered a brain disease because it alters the brain in fundamental, long-lasting ways. That is not surprising when you consider that the brain changes constantly in response to our everyday experiences.

Addiction is also a developmental disease— it typically begins in childhood or adolescence. Evidence about early drug abuse for example, finds that it starts most often in the teen years. Imagine the more dramatic changes produced by powerful substances like alcohol or heroin, on the developing brain of a young person.

Stages of Addiction

There are 3 related stages in addiction:

  1. Acute Drug Effect: At this early stage, the individual experiences the rewarding effects of the addictive drug. Dopamine is the key brain chemical involved at this stage.
  2. Transition to Addiction: At this stage, the individual transitions from recreational use to actual addiction.
  3. End Stage Addiction: At the final stage, the individual
    • Experiences a strong urge to get the addictive drug
    • Loses control of the drug-seeking desire
    • Experiences a diminished pleasure after using the addictive drug


Scientists have worked out the two major pathways in the brain responsible for addiction. First, there is the mesolimbic pathway controlled by dopamine. Second, the prefrontal cortex (the decision-making center) is responsible for controlling any inappropriate reward responses. It has been clearly shown that drug addiction can lead to physical changes in these pathways.

Neuro-imaging techniques like PET scans and MRI scans have documented actual changes in the size and shape of nerve cells in the brains of addicts. These nerve cells form networks that affect our feelings and behavior. Drugs transform the way these networks function and therefore lead to changes in behavior.

The biological link among all addictions is dopamine. This brain chemical is released during pleasurable activities ranging from sex and eating to more detrimental behaviors such as drinking and taking drugs. A powerful drug like crack cocaine floods the brain with high dopamine levels much faster than normal pleasurable activities. This flood creates the classic drug-induced feelings of exhilaration and power. These feelings can be strong.

How Addiction Works

Forcing brain cells to produce excessive dopamine on a regular basis causes them to become stressed. Eventually, the affected brain cells will begin to produce less dopamine. This will make it difficult to create even normal levels of dopamine in the brain. Over time, addicts become depressed because these low levels of dopamine dull any pleasure they may experience. They begin to rely on the drugs just to stimulate dopamine to normal levels. As the drug wears off the dopamine levels fall again. Addicts become trapped in a cycle of cravings and addiction to avoid withdrawal symptoms and depression.

In addition to the dopamine cycle, there is also damage to the part of our brain where we make decisions. Although people with addictions know the consequences of what they do, the signals that stop behavior become impaired. Genetics may also play a role in increasing someone's vulnerability to addiction.

Components of Addiction

Many addiction professionals believe addiction stems from a combination of biological, psychological, and environmental factors. The mix for some may not matter, but for others it may create an addictive personality. Some of the risk factors for addiction include: .

  • Individual Biology
    • Gender
    • Mental disorders
    • Family history of addiction
  • Environment
    • Unstable home life
    • Physical, verbal, or sexual abuse
    • Peer pressure
    • Drug use by parents
  • Drug and Brain
    • How you take the drug (oral, injection)
    • What age you start taking the drug
    • Effects of drug on your individual brain

With all these things going on, it may be difficult to identify someone who is an addict or a casual user. Here is some information that may help you pinpoint if you or someone you know has an addiction.

Diagnosing Addiction

Drug and alcohol problems can affect every one of us regardless of age, sex, race, marital status, place of residence, income level, or lifestyle. Signs of addiction may be hidden, but there are signs that something may be wrong:

  • Frequent absence from or new problems at school or work
  • Depression or anxiety
  • Weight changes
  • Frequent trauma or accidents
  • Mild tremors
  • Odor of marijuana or alcohol
  • Use of aftershave and mouthwash to hide odors

Addiction is a life long problem, but it can be treated.

Treating Addiction

Addiction treatment changes as more is understood about how it affects the brain. It can occur in different settings like hospitals, treatment facilities, or outpatient programs.

Treatment includes many factors that help to treat the whole person, not just the addiction. Sometimes treatment includes medication that helps ease the physical effects of withdrawal.

Withdrawal can be severe. Work with a health professional to help you through it.

Medication can help with some of the physical symptoms of addiction but it is equally important to address the behavioral aspects. Treatment should always include single and group therapy. This treatment will help you get to the core of the problem and prevent it from happening again.

If you suspect addiction, contact your doctor or local support group for help.


Treatment can help manage problems that lead to addiction, but it does not stop it forever. Relapse does not occur in everyone, but it is a possibility that someone recovering from an addiction must address. Relapse rates run as high as 60% among patients with drug addiction.

Relapse is not a sign of failure for the person or of the treatment. If someone relapses, they may need adjustments in their treatment, or need a better understanding of what may trigger a relapse.

Addiction has a detrimental affect on both an individual and society. The most important thing is that addiction is treatable. Getting help is always the best first step.


Family Doctor—American Academy of Family Physicians
National Institute on Drug Abuse


Canada Alcohol and Drub Rehab Programs
Centre for Addiction and Mental Health


Clay SW, Allen J, Parran T. A review of addiction. Postgrad Med. 2008;120:E01-E7.
Drugs, brains, and behavior: The science of addiction. National Institute on Drug Abuse website. Available at: Updated July 2014. Accessed August 24, 2016.
Kalivas PW, Volkow ND. The neural basis of addiction: a pathology of motivation and choice. Am J Psychiatry. 2005;162(8):1403-1413.
Mersey D. Recognition of alcohol and substance abuse. Am Fam Physician. 2003;67(7):1529-1532.
Nordstrom BR, Levin FR. Treatment of cannabis use disorders: a review of the literature. Am J Addict. 2007;16(5):331-342.
Last reviewed August 2016 by Michael Woods, MD
Last Updated: 8/24/2016

EBSCO Information Services is fully accredited by URAC. URAC is an independent, nonprofit health care accrediting organization dedicated to promoting health care quality through accreditation, certification and commendation.

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

To send comments or feedback to our Editorial Team regarding the content please email us at Our Health Library Support team will respond to your email request within 2 business days.

Home |Terms and Conditions |Concerned About Privacy? |Accessibility |Careers |For Employers and Medical Plan Providers

You may also be looking for: CVS/pharmacy | MinuteClinic | Specialty Pharmacy | SilverScript | Accordant