Influence of relative age on diagnosis and treatment of attention-deficit/hyperactivity disorder in children
Richard L Morrow1, E Jane Garland, James M Wright
1Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Victoria, BC. richard.morrow@ti.ubc.ca
Insights
Children born in December, the youngest in their grade, face higher rates of attention-deficit/hyperactivity disorder (ADHD) diagnosis and medication. This relative age effect in ADHD treatment raises concerns about potential overdiagnosis and associated risks.
Area of Science:
- Pediatric Medicine
- Neurodevelopmental Disorders
- Public Health
Background:
- The school entry cut-off date in British Columbia, Canada (December 31st) results in December-born children being the youngest in their cohort.
- This age disparity within classrooms can influence developmental assessments and diagnoses.
Purpose of the Study:
- To investigate the impact of relative age within a school grade on the diagnosis of attention-deficit/hyperactivity disorder (ADHD).
- To examine the influence of relative age on the prescription of ADHD pharmacotherapy.
Main Methods:
- A large-scale cohort study was conducted in British Columbia, Canada.
- Included 937,943 children aged 6-12 years between 1997 and 2008.
- Compared ADHD diagnosis and medication prescription rates for December-born children versus January-born children.
Main Results:
- December-born boys were 30% more likely to be diagnosed with ADHD and 41% more likely to receive ADHD medication compared to January-born boys.
- December-born girls showed even higher disparities, being 70% more likely to be diagnosed with ADHD and 77% more likely to receive medication than January-born girls.
- These findings indicate a significant relative age effect on ADHD diagnosis and treatment.
Conclusions:
- A notable relative age effect exists in the diagnosis and pharmacologic treatment of ADHD in children aged 6-12 years.
- The study highlights potential risks of ADHD overdiagnosis and overprescribing due to this age bias.
- Concerns include adverse effects such as sleep disturbances, appetite changes, growth impacts, and increased cardiovascular risks.
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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