While ADHD is a very real disorder, many argue that it's diagnosed far more often than it should be. But why are kids being misdiagnosed with this disorder? According to a new Canadian study, it might just be because they're younger than their peers.

In British Columbia, the age cutoff date for entering each grade is December 31st of whatever year — making those born in December the youngest in the class, and those born in January the eldest. Examining a cohort of more than 900,000 students, the researchers found a significant correlation between birth month and ADHD diagnosis. In fact, children born in December were 39% more likely to be diagnosed and 48% more likely to be treated with medication for ADHD than those born in January. The situation was even worse for young girls, where the December-born were 70% more likely to be diagnosed.

This research paints a picture of children who are immature due to age differences being treated as though they have a lifelong disorder.

"The relative age of children is influencing whether they are diagnosed and treated for ADHD," said lead author Richard Morrow in a statement. "Our study suggests younger, less mature children are inappropriately being labelled and treated. It is important not to expose children to potential harms from unnecessary diagnosis and use of medications."

This has an obvious two-fold negative effect. The misdiagnosed children are put on medications they don't need, and the people who argue that ADHD doesn't exist get more ammunition. The researchers argue that more stringent analysis before diagnosis could help, specifically taking into account the child's relative age to their peers, and their behavior outside of school.