The Relationship Between Age and ADHD Rates

There should be no obvious biological differences in the risk of ADHD based simply on a child's birthday. We hypothesized that for kids going to school in states with September 1 cutoffs, kids with August birthdays would be more likely to be diagnosed with ADHD. Here's what we found: In states with the September 1 cut off, kids born in August had a 34% higher rate of ADHD diagnosis and treatment.