ROCHESTER, MINN. -- A new Mayo Clinic study shows that attention-deficit/hyperactivity disorder (AD/HD) affects up to 7.5 percent of school-age children. Previous studies had estimated the occurrence of AD/HD to be anywhere between one and 20 percent of school-age children. The Mayo Clinic report, published in the March issue of Archives of Pediatrics and Adolescent Medicine, addresses the confusion about the number of children affected by AD/HD.
The study found that the lowest and most conservative estimate of AD/HD occurrence among the study subjects was 7.5 percent by age 19, based on research criteria for AD/HD. These criteria required both a clinical diagnosis of AD/HD and supporting documentation in the medical and school records.
"The 7.5 percent incidence of AD/HD from the current study includes subjects who met the most stringent research criteria and are likely to represent cases that most clinicians would regard as true cases of AD/HD," says William Barbaresi, M.D., a Mayo Clinic developmental and behavioral pediatric specialist and lead author of the study. "This study represents what we believe to be the largest population-based study of the occurrence (incidence) of AD/HD to date."
The AD/HD cases in the Mayo study were identified on the basis of rigorous research criteria, including a clinical diagnosis and extensive supporting documentation. Researchers also obtained comprehensive information about study subjects from both medical and school records.
A number of previous studies of the incidence of AD/HD relied on limited sources of information to establish the diagnosis. For example, some included only a single teacher questionnaire or lay-administered diagnostic interview.
"We took a hard look at this condition from a number of angles to help pinpoint the occurrence rates," says Dr. Barbaresi. "The results from this study provide much needed baseline information for comparison with populations in other communities. We believe this information will help us to determine how many children in the United States have AD/HD, and therefore, how many should be expected to receive treatment for this condition."
The study subjects included a total of 8,548 children born between Jan. 1, 1976, and Dec. 31, 1982, to mothers residing in the five Olmsted County, Minn., townships comprising Minnesota Independent School District #535.
AD/HD is a chronic disorder that begins in childhood and sometimes lasts into adult life. In general, children and adults with AD/HD have a difficult time paying attention and concentrating (inattention), sitting still (hyperactivity) and controlling impulsive behavior (impulsivity). These problems can affect nearly every aspect of life. Children and adults with AD/HD often struggle with low self-esteem, troubled personal relationships and poor performance in school or at work.
The study was supported by research grants from National Institutes of Health and Mayo Foundation.
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