The prevalence of ADHD diagnosis was higher among non-Hispanic, English-speaking, insured children, and even higher for children in families in which adults had more education.

"This is the first report that has enumerated the number of children who have ever had an ADHD diagnosis and are currently medicated," said Suzanne Visser, an epidemiologist with the CDC's National Center on Birth Defects and Developmental Disabilities. "We know for the first time that approximately 2.5 million children are being medicated for ADHD. That is a new number, and it is a large number."

Visser was first author of the report, which appears in this week's issue of Morbidity and Mortality Weekly, a publication of the CDC.

Inability to Pay Attention, Hyperactivity, Impulsivity

The data enables experts to make comparisons with other diseases, as well as to more correctly pinpoint the burden of ADHD, Visser added.

ADHD is a neurobehavioral disorder characterized by the inability to pay attention, hyperactivity and impulsivity. Stimulants are the first-line treatment for the disorder, but there has been much concern about the safety of this approach including, recently, debates at the US Food and Drug Administration as to whether to make labeling changes for a class of ADHD drugs that includes Ritalin.

To estimate rates of parent-reported diagnosis and treatment of ADHD, the authors of this report analyzed data from the 2003 National Survey of Children's Health. Interviewers had asked parents of children aged 4 to 17 whether a healthcare provider had ever told them their child had ADHD and, if so, if the child was currently taking medication for the condition.

In 2003, about 4.4 million children aged 4 to 17 (7.8 percent of US children) were reported to have been diagnosed with ADHD at some point.

Of these, 56 percent were reported to be taking medication for the disorder.

Finally, the report calculated that 4.3 percent of American children in this age range have ever been diagnosed and are taking medication.

Prevalence of Diagnosis

There were, however, considerable variations within these broad statistics. "We noted that children who had any form of healthcare coverage are more likely to be given a diagnosis of ADHD or medicated for it," Visser said. "We also noted some racial and ethnic differences in both diagnosis and treatment. Those require further attention."

In addition, boys were diagnosed with ADHD 2.5 times more frequently than girls, a number which is in line with previous reports.

The prevalence of diagnosis was higher among non-Hispanic, English-speaking, insured children, and even higher for children in families in which adults had more education.

Diagnosis was more frequent among males in families with incomes below the poverty levels vs. above the poverty level.

There were also striking regional differences for prevalence, with a low of 5 percent in Colorado to a high of 11 percent in Alabama, which may reflect different diagnostic practices.

The highest rates of medication treatment for ADHD were among males aged 12 years (9.3 percent) and females aged 11 years (3.7 percent). Non-Hispanic, English-speaking, insured children were again more likely to be receiving medication.

'Taking a Very Substantial Toll on Society'

State differences in medication treatment ranged from a low of 2.1 percent in California to a high of 6.5 percent in Arkansas.

Rates of medication treatment among those with a reported diagnosis of ADHD ranged from 40.6 percent in California to 68.5 percent in Nebraska.

"This doesn't come as an earth-shattering piece of news," said David Marks, a psychologist with the ADHD Center at Mount Sinai Medical Center in New York City. "Certainly, we know that ADHD has pretty far-reaching consequences. It does constitute a very substantial health burden."

"This speaks to the fact that this is a disorder that is really taking a very substantial toll on society," he added. "Individuals with ADHD across the developmental spectrum are at greater risk for a whole assortment of psychosocial consequences. In adulthood they miss work more, they're more likely to get fired, they're more likely to receive negative work reviews."

More information: Visit the National Institute of Mental Health for more on this condition.