Children who start school younger than their peers are more likely to be diagnosed with attention deficits, finds a study in the New England Journal of Medicine that raises questions about the validity of the diagnoses.
Researchers looked at the insurance records of more than 400,000 children in states with a Sept. 1 kindergarten cutoff. That means children with late August birthdays might be in the same kindergarten class as children with birthdays in early September of the prior calendar year or later—almost a full year’s difference.
The August-born children had a 30 percent greater chance of being diagnosed with ADHD than those born the previous September. That difference did not show up in states without a Sept. 1 enrollment cutoff.
