Are some ADHD-labeled kids just young for their grade?
Two independent studies have found that students whose birthdays fell just before their school's age enrollment cutoff date—making them among the youngest in their class—had a substantially higher rate of ADHD diagnoses than students who were born later. One study, using data from the Early Childhood Longitudinal Study-Kindergarten cohort, found that ADHD diagnoses among children born just prior to their state’s kindergarten eligibility cutoff date are more than 60% more prevalent than among those born just afterward (who therefore waited an extra year to begin school).