Children who are the youngest in their class are more likely than their older classmates to be diagnosed and given medication for attention-deficit hyperactivity disorder (ADHD) -- suggesting that immaturity may be part of the problem, not ADHD.

The finding is from a study of more than 900,000 Canadian children aged 6 to 12, and it dovetails with two U.S. studies that found the same thing in 2010.

In fact, the youngest boys were 30% more likely than their oldest classmates to get an ADHD diagnosis, and the youngest girls had a 70% greater chance, according to the study conducted by Dr. E. Jane Garland, a child and adolescent psychiatrist at the University of British Columbia in Vancouver and colleagues.

"The younger children in a grade were significantly more likely to be diagnosed, labeled, and treated with medication for what in some of them must simply be immaturity," Garland says.

Source: CNN