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Research

Influence of relative age on diagnosis and treatment of attention-deficit/hyperactivity disorder in children

Richard L. Morrow, E. Jane Garland, James M. Wright, Malcolm Maclure, Suzanne Taylor and Colin R. Dormuth
CMAJ April 17, 2012 184 (7) 755-762; DOI: https://doi.org/10.1503/cmaj.111619
Richard L. Morrow
From the Department of Anesthesiology, Pharmacology and Therapeutics (Morrow, Maclure, Dormuth), University of British Columbia, Victoria, BC; the Department of Psychiatry, University of British Columbia and the Mood and Anxiety Disorders Clinic, BC’s Children’s Hospital (Garland), Vancouver BC; the Departments of Anesthesiology, Pharmacology and Therapeutics and of Medicine (Wright), University of British Columbia, Vancouver, BC; the Pharmaceutical Services Division of the BC Ministry of Health (Maclure), Victoria, BC; the Drug Use Optimization branch of Pharmaceutical Services Division of the BC Ministry of Health, and Faculty of Pharmaceutical Sciences (Taylor), University of British Columbia, Vancouver, BC.
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  • For correspondence: richard.morrow@ti.ubc.ca
E. Jane Garland
From the Department of Anesthesiology, Pharmacology and Therapeutics (Morrow, Maclure, Dormuth), University of British Columbia, Victoria, BC; the Department of Psychiatry, University of British Columbia and the Mood and Anxiety Disorders Clinic, BC’s Children’s Hospital (Garland), Vancouver BC; the Departments of Anesthesiology, Pharmacology and Therapeutics and of Medicine (Wright), University of British Columbia, Vancouver, BC; the Pharmaceutical Services Division of the BC Ministry of Health (Maclure), Victoria, BC; the Drug Use Optimization branch of Pharmaceutical Services Division of the BC Ministry of Health, and Faculty of Pharmaceutical Sciences (Taylor), University of British Columbia, Vancouver, BC.
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James M. Wright
From the Department of Anesthesiology, Pharmacology and Therapeutics (Morrow, Maclure, Dormuth), University of British Columbia, Victoria, BC; the Department of Psychiatry, University of British Columbia and the Mood and Anxiety Disorders Clinic, BC’s Children’s Hospital (Garland), Vancouver BC; the Departments of Anesthesiology, Pharmacology and Therapeutics and of Medicine (Wright), University of British Columbia, Vancouver, BC; the Pharmaceutical Services Division of the BC Ministry of Health (Maclure), Victoria, BC; the Drug Use Optimization branch of Pharmaceutical Services Division of the BC Ministry of Health, and Faculty of Pharmaceutical Sciences (Taylor), University of British Columbia, Vancouver, BC.
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Malcolm Maclure
From the Department of Anesthesiology, Pharmacology and Therapeutics (Morrow, Maclure, Dormuth), University of British Columbia, Victoria, BC; the Department of Psychiatry, University of British Columbia and the Mood and Anxiety Disorders Clinic, BC’s Children’s Hospital (Garland), Vancouver BC; the Departments of Anesthesiology, Pharmacology and Therapeutics and of Medicine (Wright), University of British Columbia, Vancouver, BC; the Pharmaceutical Services Division of the BC Ministry of Health (Maclure), Victoria, BC; the Drug Use Optimization branch of Pharmaceutical Services Division of the BC Ministry of Health, and Faculty of Pharmaceutical Sciences (Taylor), University of British Columbia, Vancouver, BC.
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Suzanne Taylor
From the Department of Anesthesiology, Pharmacology and Therapeutics (Morrow, Maclure, Dormuth), University of British Columbia, Victoria, BC; the Department of Psychiatry, University of British Columbia and the Mood and Anxiety Disorders Clinic, BC’s Children’s Hospital (Garland), Vancouver BC; the Departments of Anesthesiology, Pharmacology and Therapeutics and of Medicine (Wright), University of British Columbia, Vancouver, BC; the Pharmaceutical Services Division of the BC Ministry of Health (Maclure), Victoria, BC; the Drug Use Optimization branch of Pharmaceutical Services Division of the BC Ministry of Health, and Faculty of Pharmaceutical Sciences (Taylor), University of British Columbia, Vancouver, BC.
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Colin R. Dormuth
From the Department of Anesthesiology, Pharmacology and Therapeutics (Morrow, Maclure, Dormuth), University of British Columbia, Victoria, BC; the Department of Psychiatry, University of British Columbia and the Mood and Anxiety Disorders Clinic, BC’s Children’s Hospital (Garland), Vancouver BC; the Departments of Anesthesiology, Pharmacology and Therapeutics and of Medicine (Wright), University of British Columbia, Vancouver, BC; the Pharmaceutical Services Division of the BC Ministry of Health (Maclure), Victoria, BC; the Drug Use Optimization branch of Pharmaceutical Services Division of the BC Ministry of Health, and Faculty of Pharmaceutical Sciences (Taylor), University of British Columbia, Vancouver, BC.
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Abstract

Background: The annual cut-off date of birth for entry to school in British Columbia, Canada, is Dec. 31. Thus, children born in December are typically the youngest in their grade. We sought to determine the influence of relative age within a grade on the diagnosis and pharmacologic treatment of attention-deficit/hyperactivity disorder (ADHD) in children.

Methods: We conducted a cohort study involving 937 943 children in British Columbia who were 6–12 years of age at any time between Dec. 1, 1997, and Nov. 30, 2008. We calculated the absolute and relative risk of receiving a diagnosis of ADHD and of receiving a prescription for a medication used to treat ADHD (i.e., methylphenidate, dextroamphetamine, mixed amphetamine salts or atomoxetine) for children born in December compared with children born in January.

Results: Boys who were born in December were 30% more likely (relative risk [RR] 1.30, 95% confidence interval [CI] 1.23–1.37) to receive a diagnosis of ADHD than boys born in January. Girls born in December were 70% more likely (RR 1.70, 95% CI 1.53–1.88) to receive a diagnosis of ADHD than girls born in January. Similarly, boys were 41% more likely (RR 1.41, 95% CI 1.33–1.50) and girls 77% more likely (RR 1.77, 95% CI 1.57–2.00) to be given a prescription for a medication to treat ADHD if they were born in December than if they were born in January.

Interpretation: The results of our analyses show a relative-age effect in the diagnosis and treatment of ADHD in children aged 6–12 years in British Columbia. These findings raise concerns about the potential harms of overdiagnosis and overprescribing. These harms include adverse effects on sleep, appetite and growth, in addition to increased risk of cardiovascular events.

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Canadian Medical Association Journal: 184 (7)
CMAJ
Vol. 184, Issue 7
17 Apr 2012
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Influence of relative age on diagnosis and treatment of attention-deficit/hyperactivity disorder in children
Richard L. Morrow, E. Jane Garland, James M. Wright, Malcolm Maclure, Suzanne Taylor, Colin R. Dormuth
CMAJ Apr 2012, 184 (7) 755-762; DOI: 10.1503/cmaj.111619

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Influence of relative age on diagnosis and treatment of attention-deficit/hyperactivity disorder in children
Richard L. Morrow, E. Jane Garland, James M. Wright, Malcolm Maclure, Suzanne Taylor, Colin R. Dormuth
CMAJ Apr 2012, 184 (7) 755-762; DOI: 10.1503/cmaj.111619
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