It's been known for a long, long time that if girls have ADHD they are more likely to have the inattention form, not the hyperactive, aggressive, disruptive form. Perhaps that difference in how ADHD can look is why the diagnosis is missed in girls. They may be quietly suffering and having trouble in school, but they're not disruptive.

Young Women Increasingly Turn To ADHD Drugs : Shots - Health News : NPR Sunday, March 16, 2014 @ 9:07pm