AMBULATORY PEDIATRICS Volume 4, Number 2 174 Copyright  2004 by Ambulatory Pediatric Association March–April 2004 Use of Medical Services by Methylphenidate-Treated Children in the General Population Anton R. Miller, MB, ChB, FRCPC; Jamie C. Brehaut, PhD; Parminder Raina, PhD; Kimberlyn M. McGrail, MPH; Robert W. Armstrong, MD, PhD Objectives.—To examine selected medical services for children treated for attention-deficit/hyperactivity disorder (ADHD) in a general population setting with universal health insurance. Design.—Retrospective analysis of administrative prescription and health services databases spanning from 1990 to 1996. Setting.—British Columbia, Canada. Patients.—Children (19 years of age) who had received the psychostimulant methylphenidate (MPH; Ritalin) on a chronic basis (chronic-MPH group), who had received MPH on any other basis (nonchronic-MPH group), and who were in a no-MPH comparison group. Main Outcome Measures.—The number of individuals who received any of the following services based on claims submitted by qualified practitioners: 1) emergency care, 2) critical care, 3) injury-related diagnostic and treatment services, 4) complementary and alternative medical (CAM) care, and 5) other diagnostic and treatment services (audi- ometry and allergy testing). Results.—Prevalence of services users was higher among MPH-treated than nontreated children for all types of services (except critical care services in the chronic-MPH group) after adjusting for effects of age, sex, socioeconomic status, and geographic setting, with odds ratios ranging from 1.49 to 3.17. There were no differences between the 2 MPH-treated groups. Conclusions.—Children treated with MPH for ADHD or presumed ADHD are more frequent users of a wide range of medical services than are other children. Findings support and extend existing evidence of increased use of medical services by this population of children. Findings have implications for service planning, including injury prevention, with these children. High utilization of audiometric, allergy, and CAM services warrants further scrutiny. KEY WORDS: administrative data; attention-deficit/hyperactivity disorder; children; health services use; injuries; population-based research Ambulatory Pediatrics 2004;4:174 180 T he use of whole population data can reduce threats to internal and external validity in health research by eliminating selection bias and affording very high generalizability. Whole population research is made possible in Canada by a single-payer universal insurance program (Medicare) and the capacity developed in certain provinces to use the resulting administrative data for re- search purposes. We have been investigating the treatment and correlates of attention-deficit/hyperactivity disorder From the Centre for Community Child Health Research (Drs Mill- er, Raina, and Armstrong), Children’s and Women’s Health Center of British Columbia, Vancouver, British Columbia, Canada; Depart- ment of Pediatrics (Drs Miller and Armstrong), University of British Columbia, Vancouver, British Columbia, Canada; Ottawa Health Re- search Institute (Dr Brehaut), Ottawa Hospital, Ottawa, Ontario, Canada; Department of Health Care and Epidemiology (Dr Raina), University of British Columbia, Vancouver, British Columbia, Can- ada; Department of Clinical Epidemiology and Biostatistics (Dr Rai- na), McMaster University, Hamilton, Ontario, Canada; and Centre for Health Services and Policy Research (Dr McGrail), University of British Columbia, Vancouver, British Columbia, Canada. Address correspondence to Dr Anton R. Miller, Room L408, Cen- tre for Community Child Health Research, Children’s and Women’s Health Centre of British Columbia, 4480 Oak St, Vancouver, British Columbia, Canada BC V6H 3V4 (e-mail: amiller@cw.bc.ca). Received for publication February 23, 2003; accepted October 21, 2003. (ADHD) in children and youth through analysis of ad- ministrative prescription and health services data from the province of British Columbia (population of 3.6 million at the midpoint of the study period). ADHD, a chronic neurobehavioral disorder involving dysregulation of attention, impulse control, and activity level, is of public health importance because it affects 5%–10% of school-aged children 1 and is associated with academic underachievement, disrupted family and peer re- lationships, poor self-esteem, substance abuse, and other mental health problems. 2 In addition, the medical man- agement of ADHD with stimulant drugs continues to gen- erate public and professional controversy. 3,4 Methylphe- nidate (MPH) has been the most frequently prescribed stimulant drug and the main modality of medical treat- ment used in ADHD. 5 We previously found that MPH- treated children were at increased risk for injuries result- ing in admission to hospital. 6 The aim of the present study was to investigate relationships between MPH treatment (as a proxy for ADHD) and children’s use of medical services by using practitioner claims data for services pro- vided to both hospitalized and ambulatory patients and for emergency as well as elective procedures. Recent studies have shown increased utilization of med- ical services among children diagnosed with ADHD, 7–9 but the extent to which this increased utilization is attributable