A comparison of North American versus non-North American ADHD study populations

Jan K. Buitelaar, Joanne Barton, Marina Danckaerts, Edgar Friedrichs, Christopher Gillberg, Philip L. Hazell, Hans Hellemans, Mats Johnson, Luuk J. Kalverdijk, Gabriele Masi, David Michelson, Olivier Revol, Javier San Sebastian, Shuyu Zhang, Alessandro Zuddas

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish
Pages (from-to)177-181
Number of pages5
JournalEuropean Child and Adolescent Psychiatry
Issue number3
Publication statusPublished - Apr 2006


  • Attention-deficit/hyperactivity disorder
  • Europe
  • Hyperkinetic disorder
  • North America

ASJC Scopus subject areas

  • Psychiatry and Mental health
  • Developmental and Educational Psychology
  • Pediatrics, Perinatology, and Child Health


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