Research at the National Institutes of Health and Duke University Medical Center in Durham, N.C., provides new evidence that therapeutic doses of stimulant medications, such as methylphenidate and amphetamine, do not cause cytogenetic, or chromosomal, damage in humans.

The study, published in the Journal of the American Academy of Child and Adolescent Psychiatry, looked at three measures of cytogenetic damage in white blood cells of each child participating in the study, and found no evidence of any changes after three months of continuous treatment.

"This is good news for parents," said study co-author Kristine L. Witt, a genetic toxicologist at the National Institute of Environmental Health Sciences. "Our results indicate that methylphenidate- and amphetamine-based products do not induce cytogenetic damage in children."

However, the researchers emphasize that the findings should not be interpreted as final proof of the long-term safety of stimulant drugs for the treatment of ADHD.

"More research and close monitoring of children taking these medications for extended periods of time is needed to fully evaluate the physical and behavioral effects of prolonged treatment with stimulants," study co-author Scott H. Kollins of Duke University said.