More boys are diagnosed with ADHD than girls with recent estimates of ratios ranging from 2:1 to 6:1. Experts have hypothesized the following as explanation for the observed gender difference:
A referral bias may exist that under identifies ADHD in girls.
The global deficits that have been documented in boys with ADHD, such as having a difficult time processing information, holding information on line, estimating time, and stopping a behavior once started may not extrapolate to girls.
Some research suggests that girls who are diagnosed with ADHD are largely ignored because it is believed that they are not as impaired.