High prevalence rates suggest overdiagnosis. Studies of regional variation in the United
States have shown that higher prevalence is associated with increased physician
supply, and total sales of medications to treat ADHD have soared with marketing
to physicians and directly to the general public — findings that are consistent
with overdiagnosis or overreporting. However, there are also indications of underdiagnosis.
Children with disruptive and hyperactive behaviors are the most likely
to be referred for clinical evaluation, and in children who do not have these behaviors,
ADHD may remain unidentified or untreated. In community-based
samples, the prevalence of this condition is higher among boys than among girls,
and more boys than girls have a combination of inattention and hyperactivity
rather than inattention alone.