Their study provides new evidence that therapeutic doses of stimulant medications, such as methylphenidate and amphetamine, do not cause cytogenetic (chromosomal) damage in humans.
"Our results indicate that methylphenidate- and amphetamine-based products do not induce cytogenetic damage in children," said Kristine L. Witt, M.Sc., a genetic toxicologist at the National Institute of Environmental Health Sciences (NIEHS) and co-author on the study.
For the study, the researchers included 63 children, ranging from 6-12 years of age, who met full criteria for ADHD but who had not previously been treated with stimulant medications.
Children in the study were divided into two groups and treated by a board-certified child psychiatrist with either methylphenidate (commercially available as Ritalin LA and Concerta) or with mixed amphetamine salts (Adderall and Adderall XR).
Blood samples were taken before the medication was started to establish baseline values for the cytogenetic measures that were analyzed in the study, and a second sample was collected after three months of continuous treatment. Forty-seven children completed the full three-month treatment schedule.
The researchers found no significant differences between the two groups of children with regard to age, gender, race, body weight, height, or ADHD subtype.
The groups also showed very similar ADHD symptom levels at initial screening and children in both groups responded equally well to the medication.
The researchers looked at three standard indicators of chromosomal damage: structural chromosomal aberrations (breaks in chromosomes), micronuclei (small nuclei consisting of chromosome fragments produced by breakage or whole chromosomes lost from the main nucleus after the cell divides), and sister chromatid exchanges (exchanges of genetic material between a pair of identical chromosomes).
Donald R. Mattison, M.D., and senior advisor to the director at NICHD, said: "We did not see any significant treatment-related increases in any of these three endpoints. These results add to a growing body of evidence that therapeutic levels of these medications do not damage chromosomes."
The study is published online this month in the Journal of the American Academy of Child and Adolescent Psychiatry (JAACAP).