Detailed picture of prevalence of ADHD in U.S.

Sep 4 2007

Most children in the United States who meet the medically accepted definition of Attention Deficit Hyperactivity Disorder (ADHD) have not been diagnosed by a physician, and are not consistently treated with medications, according to the first national ADHD prevalence study in children based on the "gold standard" of diagnostic criteria, according to a new study conducted by researchers at Cincinnati Children's Hospital Medical Center.

The study, published in the September 3 issue of Archives of Pediatrics & Adolescent Medicine, marks the first time researchers have been able to estimate nationwide prevalence of the disease and rates of diagnosis and treatment by using a national database and the most accepted criteria for defining specific mental health conditions. They found that 8.7 percent of children in the United States between the ages of 8 and 15 years, or approximately 2.4 million children, meet validated ADHD diagnostic criteria. However, more than half have not been diagnosed and about two-thirds were not receiving consistent treatment with ADHD medications. Moreover, girls with ADHD are more likely to go unrecognized, and the poorest children had the highest ADHD prevalence and were the least likely to have consistent treatment.

"This national study is among the most rigorous yet conducted on the U.S. prevalence of childhood ADHD and the first time we've been able to estimate nationwide treatment rates in those children who meet strict criteria for the disorder," says Tanya Froehlich, M.D., a Cincinnati Children's physician and the study's lead author. "There is a public perception that U.S. children are overdiagnosed and overmedicated for ADHD -- our study was not designed to address this issue. But what is clear from our study is that, among U.S. children currently suffering from the disorder, the opposite problem of under-diagnosis and under-treatment of ADHD appears to be occurring."

The study methodology differed from previous studies, which had come up with widely ranging estimates of ADHD prevalence, from 2 to 26%. This was the first ADHD study to use a validated national database, the National Health and Nutrition Examination Survey (NHANES) from the National Center for Health Statistics at the Centers for Disease Control and Prevention, and the first to use ADHD criteria based on the Diagnostic and Statistical Manual for Mental Disorders, Fourth Edition, considered to be the "gold standard" for defining specific mental health conditions. The study was funded by grants from the National Institutes of Health, the Ambulatory Pediatrics Association, and a Robert Wood Johnson Generalist Physician Faculty Scholar Award.

Froehlich and her colleagues found that only 47.9 percent of the U.S. children meeting ADHD criteria had reportedly been diagnosed by a health professional. Significantly more boys met ADHD criteria than girls, 11.8 vs. 5.4 percent (p <0.001). However, among children meeting criteria for the disorder, girls were a third less likely to have been diagnosed. Also, while 39 percent of those meeting ADHD criteria received some medication treatment, only 32 percent had consistent medication treatment during the last year.

"Our analysis suggests that some children with clinically significant inattention and hyperactivity may not be receiving optimal care," says Robert Kahn, M.D., a physician at Cincinnati Children's and the study's senior author. "Our report is not a call for increased use of medication, but certainly is a call for improved efforts to diagnose ADHD so that children with the disorder can receive the most appropriate treatment."

The CCHMC researchers examined NHANES data on 3,082 children gathered between 2001 and 2004, using criteria for identifying ADHD that were based on the Diagnostic and Statistical Manual for Mental Disorders, Fourth Edition, better known as DSM-IV, published by the American Psychiatric Association. DSM-IV criteria are considered to be the most accepted way of defining specific mental health conditions.

While previous studies have found no disparities by income, the Cincinnati Children's investigators did, noting that the poorest children, compared to the wealthiest, were twice as likely to meet ADHD criteria and three to five times less likely to receive consistent medication treatment. Notably, receipt of health insurance was significantly associated with prior ADHD diagnosis (p<0.05).

"Our finding of a lower likelihood of consistent ADHD medication use in the poorest children warrants further investigation and possible intervention to ensure that all children with ADHD have equitable access to treatment when appropriate," says Dr. Froehlich. "Reasons for the increased likelihood of ADHD in poorer children may include the higher prevalence of ADHD risk factors in this group, including premature birth and exposure to environmental toxicants in childhood, such as lead and prenatal tobacco smoke."

Drs. Froehlich and Kahn's co-investigators include Bruce P. Lanphear, M.D., M.P.H., and Jeffery N. Epstein, Ph.D., both at Cincinnati Children's and William J. Barbaresi, M.D., and Slavica K. Katusic, M.D., both of the Mayo Clinic, Rochester, MN.

Cincinnati Children's Hospital Medical Center, one of the leading pediatric research institutions in the nation, is dedicated to changing the outcome for children throughout the world. Cincinnati Children's ranks second among all pediatric institutions in the United States in grants from the National Institutes of Health. It has an established tradition of research excellence, with discoveries including the Sabin oral polio vaccine, the surfactant preparation that saves the lives of thousands of premature infants each year, and a rotavirus vaccine that saves the lives of hundreds of thousands of infants around the world each year. Current strategic directions include the translation of basic laboratory research into the development of novel therapeutics for the treatment of disease, and furthering the development of personalized and predictive medicine. Additional information can be found at http://www.cincinnatichildrens.org/.

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