The Weill Cornell Medical College animal study is among the first to investigate the effects of Ritalin (methylphenidate) on the neurochemistry of the developing brain.

Between 2 percent and 18 percent of U.S. children are thought to be affected by ADHD and Ritalin -- a stimulant similar to amphetamine and cocaine -- remains one of the most prescribed drugs for the behavioral disorder.

"The changes we saw in the brains of treated rats occurred in areas strongly linked to higher executive functioning, addiction and appetite, social relationships and stress, said Professor Teresa Milner, the study's lead author. "These alterations gradually disappeared over time once the rats no longer received the drug."

The scientists said their findings suggest physicians should be careful in their diagnosis of ADHD before prescribing Ritalin. That's because Ritalin might be helpful in battling the disorder but harmful if given to youngsters with healthy brain chemistry.

The research appears in the Journal of Neuroscience.