Pharmacologic treatment of attention-deficit/hyperactivity disorder in children: incidence, prevalence, and treatment patterns in the Netherlands.

BACKGROUND: The prevalence of attention-deficit/hyperactivity disorder (ADHD) and the associated use of stimulant medications may have increased in the Netherlands in recent years, but there is a lack of data to confirm this trend. This retrospective analysis examined the incidence, prevalence, and treatment pattern of ADHD among children from a large sample representation of the general population of the Netherlands and represents the first such analysis in a large cohort of European children.
OBJECTIVE: The aim of this study was to estimate the incidence and prevalence of children receiving initial pharmacotherapy for ADHD between 2000 and 2007 in the Netherlands and to describe treatment patterns (including persistence and adherence to ADHD medications) in this pediatric population.
METHODS: Prescription and hospitalization data from the PHARMO medical record linkage system database in the Netherlands (2003 to 2006) were analyzed for patients with newly prescribed ADHD medication who were aged 6 to 17 years and received follow-up for at least 12 months after treatment initiation with methylphenidate, dexamphetamine, atomoxetine, or combination therapy. The yearly incidence and prevalence of children receiving ADHD pharmacotherapy were estimated for the period 2000 to 2007. Demographic characteristics and baseline medication data at treatment initiation were collected along with data on hospitalizations and psychotropic treatments in the year before initiation of ADHD treatment.
RESULTS: Of the 4909 patients in the study cohort, 82% were male and 46% were between 6 and 9 years of age. The yearly incidence of children receiving ADHD medication--extrapolated from the PHARMO database to the Netherlands population--increased from 30 per 10,000 in the year 2000 to 75 per 10,000 in the year 2007. Prevalence rates showed a similar trend, increasing from 110 per 10,000 in 2000 to 210 per 10,000 in 2007. Prevalence and incidence rates both were consistently higher among boys than girls, although the greatest increases over time were observed in female patients. Analysis of treatment patterns revealed that most children (98%) initiated treatment with methylphenidate. Of those, 89% received an immediate-release formulation, although increased use of long-acting amphetamine and atomoxetine was apparent over the study period. Persistence and adherence rates varied according to the medications used and the prescribing physician. Antipsychotic agents and melatonin were the most commonly used therapeutics in the year before ADHD treatment initiation (6% and 4% of patients, respectively).
CONCLUSIONS: The incidence and prevalence of children treated for ADHD increased from 2000 to 2007. Most children (98%) initiated treatment with immediate-release methylphenidate.