The youngest children (bottom third) in fourth grade are 50 percent more likely to be prescribed stimulants for attention-deficit hyperactivity disorder (ADHD) by seventh grade than the oldest kids in the class, according to a new study.
These younger students were also almost twice as likely to score low on math and language arts standardized tests.
“Birthday cutoffs for school entry necessarily lead to an age span of at least 12 months within a classroom,” said the authors.
“At age 5, this span accounts for 20 percent of the child’s age and presents a difference in maturity and performance between the youngest and the oldest child in class.”
Researchers from the Mount Sinai School of Medicine reached this conclusion from a population-based study of children in Iceland.
Since the gap seems to persist through age 14 in the study, “this should be taken into account when evaluating children’s performance and behavior in school to prevent unnecessary stimulant treatment,” to make sure kids aren’t getting a lifelong label simply because of immaturity compared to older peers, said the researchers.
Given controversy on the subject, the researchers used national databases from Iceland to gather information on standardized test results and psychotropic drug prescriptions among all 11,785 children tested at age 9 to 12 there.
The youngest children in fourth grade, born in September to December, came in 10 percentiles lower on average on standardized tests in both math and language arts compared to the oldest third, born in January to April.
By seventh grade, the difference was smaller but still significant. Averages were seven percentiles lower for the youngest third versus the oldest third in both areas.
Prescriptions of stimulant medication for ADHD as a measure of behavioral difficulties were highest in the youngest children. The rates increased from 5.3 percent in the oldest third to 5.6 percent in the middle group born in May to August to 8 percent for the youngest third.
Both standardized test scores and ADHD prescriptions showed significant signs of age separation for girls as well as boys.
The researchers cautioned that these measures may only partially predict long-term academic and psychiatric outcomes. They also couldn’t rule out possible undertreatment of ADHD in the oldest children as the problem rather than overtreatment in the youngest.
However, parents might want to consider these findings in deciding when to start their children in school, suggest the researchers.