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 com
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