title: A comparison of North American versus non-North American ADHD study populations.
abstract: Few large, prospective clinical studies in Europe have assessed the validity and applicability of research methods used to study ADHD in North America. To assess comparability of study populations, we examined baseline patient characteristics from a group of North American studies against those of a large European/African/Australian study. All studies used identical diagnostic assessments and inclusion criteria, with ADHD diagnosis and the presence of comorbid psychiatric conditions confirmed using the KSADS-PL. Raters were trained and assessed to ensure uniform diagnostic and symptom severity rating standards. Six hundred and four patients (mean age = 10.2 years) enrolled in the non-North American study, and 665 patients (mean age = 10.4 years) enrolled in the North American study. The proportion of girls was higher in the North American studies (29.2% vs. 10.4%, p < 0.001). In both groups, most patients had a positive family history of ADHD and previous stimulant treatment. Fewer had the inattentive subtype of ADHD, and mean severity was slightly higher in the non-North American study. Results demonstrate that, when a uniform set of rigorous, standardized diagnostic criteria are used by skilled clinicians, the patient populations identified are generally similar. This supports the practice of generalizing results from treatment studies across geographies.
authors.affiliation: Dept. of Psychiatry, Academic Centre for Child & Adolescent Psychiatry, University Medical Centre St. Radboud, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands. j.buitelaar@psy.umcn.nl
authors.forename: Jan K
authors.initials: JK
authors.lastname: Buitelaar
authors.forename: Joanne
authors.initials: J
authors.lastname: Barton
authors.forename: Marina
authors.initials: M
authors.lastname: Danckaerts
authors.forename: Edgar
authors.initials: E
authors.lastname: Friedrichs
authors.forename: Christopher
authors.initials: C
authors.lastname: Gillberg
authors.forename: Philip L
authors.initials: PL
authors.lastname: Hazell
authors.forename: Hans
authors.initials: H
authors.lastname: Hellemans
authors.forename: Mats
authors.initials: M
authors.lastname: Johnson
authors.forename: Luuk J
authors.initials: LJ
authors.lastname: Kalverdijk
authors.forename: Gabriele
authors.initials: G
authors.lastname: Masi
authors.forename: David
authors.initials: D
authors.lastname: Michelson
authors.forename: Olivier
authors.initials: O
authors.lastname: Revol
authors.forename: Javier San
authors.initials: JS
authors.lastname: Sebastian
authors.forename: Shuyu
authors.initials: S
authors.lastname: Zhang
authors.forename: Alessandro
authors.initials: A
authors.lastname: Zuddas
mesh_terms: D018759:Adrenergic Uptake Inhibitors / Q000627:therapeutic use; D000069445:Atomoxetine Hydrochloride; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis* / Q000453:epidemiology / Q000208:ethnology*; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D011437:Propylamines / Q000627:therapeutic use; D011446:Prospective Studies; D012720:Severity of Illness Index; D017678:Sex Distribution; D014481:United States / Q000453:epidemiology
chemical_list: D018759:Adrenergic Uptake Inhibitors; D011437:Propylamines; D000069445:Atomoxetine Hydrochloride