How Does the Brain Become Addicted?

Typically it happens like this:

• A person takes a drug of abuse, be it marijuana or cocaine or even alcohol, activating the same brain circuits as do behaviors linked to survival, such as eating, bonding and sex. The drug causes a surge in levels of a brain chemical called dopamine, which results in feelings of pleasure. The brain remembers this pleasure and wants it repeated.

• Just as food is linked to survival in day-to-day living, drugs begin to take on the same significance for the addict. The need to obtain and becomes more important than any other need, including truly vital behaviors like eating. The addict no longer seeks the drug for pleasure, but for relieving distress.

• Eventually, the drive to seek and use the drug is all that matters, despite devastating consequences.

• Finally, control and choice and everything that once held value in a person's life, such as family, job and community, are lost to the disease of addiction.

What brain changes are responsible for such a dramatic shift?

Research on addiction is helping us find out just how drugs change the way the brain works. These

• Reduced dopamine activity. We depend on our brain's ability to release dopamine in order to experience pleasure and to motivate our responses to the natural rewards of everyday life, such as the sight or smell of food. Drugs produce very large and rapid dopamine surges and the brain responds by reducing normal dopamine activity. Eventually, the disrupted dopamine system renders the addict incapable of feeling any pleasure even from the drugs they seek to feed their addiction.

• Altered brain regions that control decisionmaking and judgment. Drugs of abuse affect the regions of the brain that help us control our desires and emotions. The resulting lack of control leads addicted people to compulsively pursue drugs, even when the drugs have lost their power to reward.

by Nora D. Volkow, M.D.