| Prevalence |
The estimated prevalence of ADHD in school-aged children increased from 6% in 1997 to almost 10% in 2007 (National Center for Health Statistics, 2008; Visser et al., 2010). Prevalence among American adults is about 4% (Kessler, Adler, et al., 2006). |
| Comorbidity |
Common comorbid disorders include mood and anxiety disorders, learning disorders, and oppositional defiant disorder (American Psychiatric Association, 2013; Larson et al., 2011). Up to half of children with ADHD also have oppositional defiant disorder. Children with hyperactive and impulsive symptoms are more likely to be diagnosed with oppositional defiant disorder or conduct disorder than are those with inattentive symptoms (Christophersen & Mortweet, 2001). |
| Onset |
Children are not usually diagnosed before age 4 or 5 because the range of normal behavior for preschoolers is very wide. In younger children, the diagnosis is generally based more on hyperactive and impulsive symptoms than on inattention symptoms. |
| Course |
Symptoms of ADHD become obvious during the elementary school years, when attentional problems interfere with schoolwork. By early adolescence, the more noticeable signs of hyperactivity—difficulty sitting still, for example—typically diminish to a sense of restlessness or a tendency to fidget. Almost a third of childhood cases carry over into adulthood (Barbaresi et al., in press). |
| Gender Differences |
Males are more likely—in one survey, more than twice as likely—to be diagnosed with ADHD, particularly the hyperactive/impulsive type, although this gender difference may reflect a bias in referrals to mental health clinicians rather than any actual difference in prevalence (National Center for Health Statistics, 2008). |
| Cultural Differences |
In the United States, non-Hispanic White children are more likely to be diagnosed with ADHD than are Hispanic or Black children (Havey et al., 2005; Stevens et al., 2005). Worldwide, the prevalence of the disorder among children averages about 5% (Polanczyk & Rohde, 2007), although some studies find higher prevalence rates (Bird, 2002; Ofovwe et al., 2006); variability across countries can be explained by the different thresholds at which behaviors are judged as reaching a symptomatic level, as well as somewhat different diagnostic criteria (Bird, 2002). |
| Source: Unless otherwise noted, the source for information is American Psychiatric Association, 2000. |