It's reported that the active ingredient in ADHD medications such as Ritalin has been shown to delay the onset of puberty in male monkeys. This came in a study published online at the Proceedings of the National Academy of Sciences.

Scientists working on the study noticed the rhesus monkeys given a high dose of MPH showed significantly lower testosterone levels, significantly slower rates of testicular decent and reduced testes size.  This means their onset of puberty is delayed.

The study’s authors say male rhesus monkeys and male humans have similar puberty processes - so the monkeys are good models for how the drug may affect humans.

The authors of the study say they were looking for evidence that the drug methyl-phenidate has adverse effects on DNA, and they were completely surprised by this finding.  It's something they never expected to find.

About 3 to 5 percent of school-aged children have Attention Deficit Hyperactivity Disorder (ADHD), which is characterized by a lack of attention, hyperactivity and impulsive behavior. More boys are affected than girls.

Dr. Donald Mattison of the Eunice Kennedy Shriver National Institute of Child Health and Human Development says parents of children who take this drug for ADHD should talk with their child’s doctor before making any changes to their medication.

Mattison also says the effects of the drug were not permanent, and these surprising findings are only preliminary and need further study.