Age, sex, may confound ADHD diagnosis.

In ADHD, Brain Disorders, Brain Science, Memory and Learning by Brainy Days Ahead

New research has found the youngest children in West Australian primary school classes are twice as likely as their oldest classmates to receive medication for Attention Deficit Hyperactivity Disorder (ADHD). The proportion of boys receiving medication (2.9%) was much higher than that of girls (0.8%).