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Changes in brain increase teen
risk of drug addiction

A study from Yale University suggests that drug addiction is a developmental disorder,
one that affects adolescents in particular. The reason: Areas of a teenager's brain that control impulsive behavior are not fully formed, while brain circuits that reinforce drug use are already in high gear.

Dr. R. Andrew Chambers, assistant professor of psychiatry at Yale School of Medicine, led the study, which was published in the June 2003 issue of The American Journal of Psychiatry. Chambers and his colleagues based their findings on a review of 140 earlier studies of addiction and brain development.

During adolescence, the human brain begins to release more chemicals associated with new experiences and the desire to repeat them. One of the chemicals is dopamine, a neurotransmitter involved in many forms of addiction.

Activities that increase dopamine production are highly reinforcing. These activities lead primitive parts of the brain to broadcast a message--in effect: That feels good. Do it again.

Overall, this change in brain chemistry serves a positive purpose. Adolescents need to increase their range of experiences and develop many new skills. Instead of playing with toy cars, for example, adolescents learn to drive a real car. They need experiences like these in order to become independent, self-regulating adults in the future.

The problem is that adolescent brains reinforce novel experiences in ways that are much stronger--and longer lasting--than those experienced by children or adults. Also, areas of the brain that adults use to weigh the risks of behaviors are still developing in adolescents.

The bottom line: Teenagers are more likely to experiment with drugs than people in other age groups. And, those experiments are more likely to produce addiction.

"We used to think that the brain you're born with is essentially the brain you live with for the rest of your life," says Stuart Reedy, supervisor of Intake Services at the Hazelden Center for Youth and Families in Plymouth, Minn. "Now we know that's not true. The so-called executive functions of the brain are still under construction during adolescence, while the limbic system, which is tied to strong emotion, is already active."

The Yale study has four key implications.

First, the longer that adolescents can delay alcohol and other drug use, the less their chance of becoming addicted. Previous research, including a January 1998 study from the National Institute on Alcohol Abuse and Alcoholism (NIAAA), links early drug use with significantly higher risk of addiction. Programs to prevent drug use must start early, before kids become teenagers.

Second, we can no longer afford to dismiss teenage drug experiments as harmless rites of passage. Even a single incident of alcohol or other drug use can have implications for a lifetime. It means early intervention programs for substance abusers are increasingly important. The NIAAA reports that nearly 50 percent of adolescents have had at least one drink by the time they reach the eighth grade--and over 20 percent report having been drunk.

Third, we need to look beyond genetic influences and peer pressure to use drugs as sources of addiction risk. "Several lines of evidence suggest that sociocultural aspects particular to adolescent life alone do not fully account for greater drug intake," says Chambers. The Yale study, he adds, confirms that "a neurodevelopmental stage common to virtually everyone regardless of genetic make-up confers enhanced neurobiological vulnerability to addiction."

Finally, Reedy points out, "among teenagers who enter treatment for addiction, many of the behaviors that we might view as ‘out of control' are simply adolescent behaviors--products of a developing brain. While in treatment, teenagers often need more external controls and structures than we give to adults. When we remember this, we're more likely to provide treatment that works."

 
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