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Adolescent Drug Use Creates Long-Term Imbalance

Even commonly prescribed amphetamines may lead to addictive behavior.

TUESDAY, Nov. 5, 2002 (HealthDayNews) -- Drug use during adolescence, including such commonly prescribed drugs as Ritalin, may upset brain chemistry more than any other time in a person's life, new research says.

The findings should help scientists better understand why addictions generally begin during adolescence, and what the long-term risks result.

"This is a major public health question," says the lead researcher, Dr. Michelle Ehrlich, a neurology professor at Thomas Jefferson University in Philadelphia. "The adolescent brain appears to be more sensitive to certain effects of these psycho-stimulant drugs. We need to see whether this sensitivity leads to permanent brain changes and behavior changes."

In the study, which just appeared in the Journal of Neuroscience, the researcher gave cocaine and amphetamine to groups of adult, adolescent and baby mice every day for a week. Then they compared the chemistry in two sections of the mice brains against that of a control group. Because mice have many of the same brain functions as humans, scientists believe the results should shed light on our brains, Ehrlich says.

After taking the drugs, all the mice had elevated levels of an addiction-marking protein in the part of the brain that controls movement and hyperactivity. But adolescent mice also had high levels of the protein in the part of the brain that controls the "reward" mechanism.

Because of that chemical imbalance, adolescents may depend on drugs to stimulate their reward mechanism, leading to addictive behavior, Ehrlich says. Meanwhile, other studies have shown that the protein, called Delta FosB, stimulates other chemical responses in the brain months after drug use has stopped, which may contribute to drug cravings.

"The implications are that there is an increased adaptation in the younger brain than in the older brain to these psycho-stimulants," Ehrlich says.

But Ehrlich isn't worried only about the effects of illegal drugs. The same long-term changes in brain chemistry may also occur after adolescents take prescribed amphetamine.

"Amphetamine is one of the most commonly used drugs for attention deficit disorder. Ritalin is one of the most well-known ones," Ehrlich says. "I prescribe these drugs. I work with children on these drugs. I'm not saying we shouldn't use them, but we should know about their long-term effects."

In some cases, the risks of prescribing amphetamine drugs are worthwhile, says Dr. Eric Nestler, chairman of the psychiatry department at the University of Texas Southwestern Medical Center. But Nestler, who was one of the first researchers to discover Delta FosB, says such drugs are prescribed too often, when the risks aren't worthwhile.

"There has to be a concern," he says. "Kids with attention deficit disorder are really impaired. A drug like Ritalin works well with those conditions, and to deny it to a kid who really need it is a disservice. The problem comes when the diagnosis of attention deficit disorder is made too frequently."

So far, though, no one has studied whether Ritalin and other prescribed drugs raise the level of Delta FosB like cocaine and amphetamine, Nestler says. "That would be an interesting study," he says.

Nestler says he is surprised that Erlich's team didn't see higher Delta FosB levels in both parts of the adult mouse brain. In his research, he found that both adolescent and adult mice have elevated levels, although he thinks he used a more sensitive method of detecting Delta FosB.

Still, if Ehrlich's research shows that adolescents have a higher level of Delta FosB than do adults, it reveals key evidence about the addiction process, he says.

"This is the first finding to suggest that the adolescent brain is more sensitive. That is very interesting," Nestler says.

What To Do

To learn more about these drugs, visit this site at the California State University at San Marcos. Or for more information about how amphetamine is prescribed to treat attention deficit/hyperactivity disorder, try the National Center for Birth Defects and Developmental Disabilities.

SOURCES: Michelle Ehrlich, M.D., professor of neurology, Jefferson Medical College, Thomas Jefferson University, Philadelphia; Eric Nestler, M.D., Ph.D., chair, department of psychiatry, University of Texas Southwestern Medical Center, Dallas; Nov. 1, 2002, Journal of Neuroscience
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