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

Abstract

Research CMAJ 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 attentiondeficit/ 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. Abstract © 2012 Canadian Medical Association or its licensorsCMAJ, April 17, 2012, 184 (7) 755American use of medications to treat ADHD exceeds that of other developed countries, such as Canada. 18,19We were interested in knowing whether the effect of relative age was inherent in the American context (owing to underlying factors such as differences in the health care system, cultural attitudes or marketing by the pharmaceutical industry), or whether it would be present in the different context of Canada. We conducted a cohort study to explore the influence of relative age on the diagnosis and treatment of ADHD in a large sample of children with data from a nearly universal public health plan in British Columbia, Canada. The cut-off date of birth that allows entry into kindergarten or grade 1 in this province is December 31. Consequently, children born in December are typically the youngest in their grade. We hypothesized that the younger children within each grade would be more likely to have a diagnosis of ADHD and to have received prescriptions for the medications used to treat ADHD. Methods Data sourcesWe used linked data from provincial administrative health databases for prescription drugs (PharmaNet), physician services (Medical Services Plan) and hospital admissions (Canadia...

ADHD: a critical update for educational professionals

“…Several studies (Elder, 2010; Evans, Morrill, & Parente, 2010; Halldner et al, 2014; Morrow et al, 2012; Zoëga, Valdimarsdóttir, & Hernández-Díaz, 2012) showed that relative age is a significant determinant of ADHD diagnosis and treatment. Overall, the youngest children in class are twice as likely as their classmates to receive a diagnosis of ADHD and medication.…”

School Starting Age and Cognitive Development

“…As 1 See for example, Bedard and Dhuey (2006), Datar (2006), Crawford et al (2007), Puhani and Weber (2007), McEwan and Shapiro (2008), Lubotsky (2009), Smith (2009), Kawaguchi (2011), Cook andKang (2016), Lubotsky and Kaestner (2016), McAdams (2016), Landerso et al (2017b) and Attar and Cohen-Zada (2017). Some other outcomes investigated in this literature include high school leadership (Dhuey and Lipscomb 2008), pre-academic university tracks and enrollment in selective universities (Bedard and Dhuey 2006), and disability identification and special education (Dhuey and Lipscomb 2010;Elder and Lubotsky 2009;Evans et al 2010;Morrow et al 2012) 2 For instance, Fredriksson and Ockert (2014) and Kawaguchi (2011) find that older children at school entry earn higher wages; and Du et al (2012) find that they are more likely to be a corporate CEO. In contrast, Black et al (2011), Dobkin and Ferreira (2010), and Fertig and Kluve (2005) find no such long-term wage effects.…”

Overdiagnosis: How Our Compulsion for Diagnosis May Be Harming Children

“…In evaluating the importance of overdiagnosis in a condition at the population level, we propose focusing on the frequency of overdiagnoses relative [83][84][85] Although this phenomenon has been labeled overdiagnosis, one could argue that misdiagnosis is more appropriate (ie, immaturity is misdiagnosed as ADHD).…”