The study also found that "being younger relative to one's classmates affects academic performance throughout childhood," Zoega said.
Richard Morrow, a health research analyst at the University of British Columbia who studies ADHD, said the findings are consistent with those from other countries.
"In the education system, it leads to the question, 'What strategies or resources do we need to help ensure the well-being of all children in the classroom, where children vary in age by up to a year?' " he asked. "Parents need to be aware that if behavioral issues arise for their child, this may be related to their child's relative age in the classroom.
"Similarly, doctors need to consider a child's relative age in school or other settings such as athletics before making a diagnosis or writing a prescription," Morrow added. "Lastly, we may need to revisit how the diagnosis is defined to lessen the risk of inappropriate diagnosis."
The findings appear online Nov. 19 and in the December print issue of the journal Pediatrics.
So what can be done?
"Children behave and perform according to their own maturity level within the classroom," Zoega said. "Being younger relative to one's classmates affects academic performance throughout childhood. When evaluating whether a child has ADHD, this should be taken into account to prevent unnecessary diagnoses and prescribing of stimulants."
For more about ADHD, try the U.S. National Library of Medicine.
SOURCES: Helga Zoega, Ph.D., postdoctoral fellow, Institute for Translational Epidemiology, Mount Sinai School of Medicine, New York City; Richard Morrow, health research analyst, University of British Columbia, Vancouver; December 2012 Pediatrics
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