Recall, we mentioned the central debate seems to be whether or not ADHD is a bonafide disorder. If ADHD is a disorder, we would expect to see it equally affect everyone. However, that is not the case. In the United States, the majority of children with ADHD come from just a few geographic regions. Moreover, they are mostly white males from affluent families. Young males covered by private insurance, have even higher rates of diagnosis. These factors have led to concerns that ADHD is becoming a fad diagnosis. In many professional circles, the tendency for certain diagnoses to become overly popular is jokingly referred to as the Diagnosis Du Jour.
ADHD prevalence rates in the United Stated vary by state and region. As of 2011, Nevada had the lowest rate of currently diagnosed children aged 4 to 17 years at 4.2%. Kentucky had the highest rate of 14.8%. People familiar with United States culture and sub-cultures readily recognize these two states (and surrounding regions) are culturally quite different, but why there are such differences between regions remains unclear (Center for Disease Control, 2011).
Other researchers have found that prevalence rates seem to vary by type of community. In impoverished communities, the diagnosis is far less common. The exception occurs in many Native American reservation communities. In these impoverished communities, ADHD is a common diagnosis even for very young children. Some research found larger prevalence rates in larger cities in the U.S. with rates reported as high as 10-15%. In general, rates are much higher in urban areas than in rural ones. In addition, the use of medication treatment varies across the country with Nevada at a low of 2.2%, to a high of 10.4% in Louisiana (Holland & Riley, 2014).
Although ADHD is more frequently diagnosed in the United States, it has been found in every country that has been studied. A review of the literature conducted in 2003 found that rates of ADHD in other countries were at least as high as it is in the United States. Further studies were conducted and found the same result: ADHD has a worldwide uniform prevalence rate in industrialized societies. Prevalence rates range from 1.7% to 10% in Canada, Germany, the Netherlands, New Zealand, Norway, Puerto Rico, and the United Kingdom. (Faraone, Sergeant, Gillberg, & Biederman, 2003).
Another study took a bold step to suggest that ADHD is influenced by the expectations of the adults in that child's culture. This implies that for some cultures ADHD would not be as noticeable because it symptoms not considered problematic by the adults in that culture. This epidemiological study, published on the ADHD Institute website, found that the prevalence of ADHD in Europe was just under 5%. The researchers suggest that prevalence rates may be influenced by the source of information; and the type of society; as well as global variation of diagnostic criteria (Burden of ADHD: Epidemiology, n.d.).
It is unclear whether socioeconomic status, stigma, and/or racial biases influence prevalence rates. (Holland & Riley, 2014) More research is needed before any definitive understanding will be available.
Gender differences: Why is ADHD more common in boys than girls?
Boys (12.1%) are diagnosed with ADHD more than girls (5.5%). This trend continues into adulthood. In fact, males of all ages tend to display significantly more hyperactivity, and slightly more symptoms of inattention than do females.
The difference in prevalence rates between males and females is an interesting phenomenon. Boys are more often diagnosed hyperactive/impulsive type. These active behaviors are difficult to ignore. However, even boys with the predominantly inattentive type tend to fool around and become noticeably off task. This also draws the attention of adults. In contrast, girls are more often diagnosed inattentive type. But, their inattentive style is also less noticeable than boys. Girls' inattention tends toward quiet daydreaming. This quiet, internal behavior can more easily be overlooked. These different tendencies offer one possible explanation for the different rates between boys and girls. However, it remains to be determined if there are true gender-based differences in genetic susceptibility to ADHD or, if distracted females are simply less likely to be noticed than rambunctious males. Research is being conducted to determine the source of these differences.