National trends in the prevalence of attention-deficit/hyperactivity disorder and the prescribing of methylphenidate among school-age children: 1990-1995

It has been reported that during the past decade the prevalence of attentio n-deficit/ hyperactivity disorder (ADHD) (ICD-9-CM code 314.00 or 314.01) a nd its pharmacologic treatment have increased dramatically in the United St ates. Herein, a single national data source is used to discern trends in th e prevalence of U.S. office-based visits resulting in a diagnosis of ADHD, and trends in the prescribing of stimulant pharmacotherapy (including methy lphenidate) for its treatment. Data from the National Ambulatory Medical Ca re Survey (NAMCS) for the years 1990 through 1995, for children aged 5 thro ugh 18 years, were utilized for this analysis. Results indicate that the nu mber of office-based visits documenting a. diagnosis of ADHD increased from 947,208 in 1990, to 2,357,833 in 1995, Between 1990 and 1995, the number o f visits by girls diagnosed with ADHD rose 3.9-fold (p<0.05), and the mean patient age increased by more than 1 year, from 9.7 in 1990, to 10.8 in 199 5 (p<0.05). The percentage of office-based visits resulting in a diagnosis of ADHD increased from 1.1% of all visits ill this age group in 1990, to 2. 8% by 1995. We discerned a 2,3-fold increase (p<0.05) in the population-adj usted rate of office-based visits documenting a diagnosis of ADHD; a 2.9-fo ld increase (p<0.05) in the population-adjusted rate of ADHD patients presc ribed stimulant pharmacotherapy; and a 2.6-fold increase (p<0.05) in the po pulation-adjusted rate of ADHD patients prescribed methylphenidate.