Between the ages of 3 and 17, boys are diagnosed with ADHD at a rate of 13% while girls are diagnosed at a rate of 6% (CDC.gov).
Why are girls diagnosed less frequently?
Part of the explanation might be related to differing views of ADHD in girls vs. boys. When we picture an 8- year-old boy with ADHD, we imagine an active youngster who calls out in class, can’t sit still, loses his coat somewhere at school and forgets his homework. There are 8-year-old girls, of course, who fit the description of the 8-year-old boy. Those girls are likely to be referred for intervention or evaluation because the behavior disrupts their performance in the classroom and interferes with the education of other students.
The presentation for girls may be somewhat different.
They are quiet in class. The teacher may have suspected that the female student was daydreaming, but could not be sure, because the student seemed to be looking at the teacher during class. This girl might also forget to bring homework to school, lose her jacket and have trouble following exact directions. She is not disrupting the class with impulsive behavior. She is quietly tuned out or disengaged.
Adults might wonder if the female student is depressed or anxious. Sometimes she chews on her shirt, and she does not participate much in class. Dr. Patricia Quinn writes that anxiety is self-reported far more often in girls with ADHD than boys with the same diagnosis.
Maureen Connolly speaks more about ADHD in Girls in her article, ADHD in Girls: The Symptoms that are Ignored in Females.