The Science of Addiction

IMAGE 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 powerful.

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