Vidyya Medical News Service
Volume 6 Issue 204 Published - 14:00 UTC 08:00 EST 22-Jul-2004 Next Update - 14:00 UTC 08:00 EST 23-Jul-2004
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Study sheds new light on mechanism behind stimulant medication for ADHD

New research involving the drug methylphenidate (Ritalin) is shedding light on how certain stimulant drugs impact the brain to improve attention and concentration for certain academic tasks. Methylphenidate is used widely to treat attention deficit hyperactivity disorder (ADHD), a neurological disorder characterized by developmentally inappropriate behavior, including poor attention skills, impulsivity, and hyperactivity. It is estimated to affect between 3 and 5 percent of the U.S. school-aged population, and also can affect adults.

In the study, the researchers, including NIDA Director Dr. Nora Volkow and scientists at Brookhaven National Laboratory, used positron emission tomography (PET) to examine brain chemistry in 16 healthy adult men and women without ADHD who were given methylphenidate or a placebo. After receiving the drug or placebo, the participants performed a series of mathematical tasks or looked at neutral images of scenery.

The PET scans showed that when participants received methylphenidate and worked through the mathematical tasks, they experienced a significant increase in extracellular dopamine. Dopamine is a brain chemical involved in pleasure/reward and motivation. These participants were also more likely to describe the mathematical tasks as interesting, exciting, and motivating.

A similar rise in extracellular dopamine levels was not seen among the participants who received the placebo and performed tasks, or those who received methylphenidate and viewed the neutral images. In addition, when the tasks were paired with placebo, participants were more likely to describe them as tiresome and boring

CONCULSION: Stimulant drugs like methylphenidate work to raise levels of extracellular dopamine, a key chemical in motivation, which can enhance interest in performing an academic task. A better understanding of this mechanism may lead to the development of other medications that have similar chemical effects in the brain, and help people with ADHD improve focus on and motivation for performing academic tasks. The study findings also support developing educational strategies that make schoolwork more interesting as a nonpharmacologic way to treat ADHD.

The study was funded by NIDA and the Department of Energy. It was published in the July 2004 issue of the American Journal of Psychiatry.

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