Final answer:
The incidence of ADHD among school-age children is approximately 5-10%, with ADHD being associated with atypical variations in brain development and oftentimes co-occurring with other disorders.
Step-by-step explanation:
The incidence of Attention Deficit Hyperactivity Disorder (ADHD) among school-age children varies in different studies and reports. According to one of the sources you provided, ADHD affects approximately 9 percent of U.S. children. Another source indicates that approximately three to five percent of children and adults are affected by ADHD. Taking these figures into account, the closest answer to the question of the incidence of ADHD among school-age children would be b. 5-10%.
ADHD is associated with atypical variations in brain development which can lead to symptoms such as inattention, impulsivity, and hyperactivity. Some individuals may have a subtype called attention deficit disorder (ADD), which lacks the hyperactive component. ADHD often co-occurs with other disorders such as depression or obsessive-compulsive disorder (OCD), complicating the lives of those affected by it.