Youngest Kids in Grade More Likely to Be Diagnosed with ADHD

A new study out of Canada suggests that some doctors are labeling children's immaturity as attention-deficit/hyperactivity disorder (ADHD) and prescribing them unnecessary medications.

Researcher Richard L. Morrow and his team looked at the medical records of nearly one million 6-12 year-olds and found that the youngest kids in a grade were 39% more likely to be diagnosed with ADHD. Moreover, they were nearly 50% more likely to be receiving medication for treatment than the oldest kids in the class. The discrepancy was even greater for girls; girls born in December (the Canadian cut off date for entering kindergarten) were 70% more likely to be labeled with the condition and 77% more likely to be medicated than kids born in January. A 2010 study on a smaller group of US school children had similar results.

Side effects of ADHD drugs are common and include sleep and appetite problems, stomachache, and mood swings. Little is known about their long-term effects. Kids who are being treated for ADHD may also be prone to psychological problems because they are stigmatized or rejected by their peers.

Morrow points out there is no objective criteria for ADHD, and doctors are likely to be leaning heavily on school's reports of factors such as classroom performance and self control. Nor are there hard and fast rules for children's behavior at a given age.

The study recommends that when evaluating a young patient for ADHD, doctors into account their relative age and also look at how they act outside of school at home, on sports teams, or participating in other extra curricular activities. "It's good to do everything we can to avoid medicalizing the normal range of childhood behavior," said Morrow in a statement. "Differences in behaviors can arise because of differences in age or just from the fact that children mature at naturally different rates." The CDC reports that about 9.5% 4-of 17 year-olds in the US have been diagnosed with ADHD making it the most common neurobehavioral disorder in children.

More from Shine on Yahoo! Canada

Top 10 myths about ADHD

Surprising risk factor for autism

Best supplements and vitamins for a healthy pregnancy