The Canadian Medical Association Journal published a study last month looking at ADHD diagnoses in children between the ages of 6-12 in BC. They found that the youngest children in the class - those born in December - were much more likely to be diagnosed with ADHD than those who were born in January.
Here's a summary of the article from Medical News Today.
The Bridgeway Team
Immaturity May Lead To Misdiagnosis Of ADHD
The youngest children in the classroom are significantly more likely to be
diagnosed with attention-deficit/hyperactivity disorder (ADHD) - and prescribed medication -
than their peers in the same grade, according to a study just published in
CMAJ (Canadian Medical Association Journal).
ADHD, which is often
treated with prescription medication, is the most commonly diagnosed behavioural
disorder in children. Two recent studies have shown a link between the relative
age of children and diagnosis of ADHD and prescription of medication. Younger
children in the same grade as children who may be almost a year older may appear
to be immature compared with their older peers. This apparent lag in maturity
has been called the "relative-age effect" and influences both academic and
Researchers from the University of British
Columbia were interested to see whether this relative age effect was present in
Canada and looked at a large cohort of 937 943 children in British Columbia, a
province where the cut-off for entry into kindergarten or grade one is Dec. 31.
The research included children who were between 6 and 12 years at any point
during the 11-year study conducted from Dec. 1, 1997 to Nov. 30, 2008.
Researchers found that children were 39% more likely to be diagnosed and
48% more likely to be treated with medication for ADHD if born in December
compared to January. Due to the Dec. 31 cut-off birth date for entry into school
in British Columbia, children born in December would typically be almost a year
younger than their classmates born in January.
"The relative age of
children is influencing whether they are diagnosed and treated for ADHD," said
lead author Richard Morrow, University of British Columbia. "Our study suggests
younger, less mature children are inappropriately being labelled and treated. It
is important not to expose children to potential harms from unnecessary
diagnosis and use of medications."
There are significant health and
social ramifications of inappropriate diagnosis of ADHD. Medication to treat
ADHD can have negative health effects in children such as sleep disruption,
increased risk of cardiovascular events and slower growth rates. As well,
younger children who have been labelled ADHD may be treated differently by
teachers and parents, which could lead to negative self-perception and social
"This study raises interesting questions for clinicians,
teachers and parents," noted coauthor and psychiatrist Jane Garland, University
of British Columbia and BC Children's Hospital. "We need to ask ourselves what
needs to change. For example, attention to relative age of children for their
grade and more emphasis on behaviour outside the school setting might be needed
in the process of assessment."
Although the prevalence of ADHD diagnosis
and treatment is about three times higher in boys than girls, the effect of
relative age applied to both. In fact, girls born in December and typically
younger within their grade were 70% more likely to be diagnosed with ADHD than
girls born in January.
"The potential harms of overdiagnosis and
overprescribing and the lack of an objective test for ADHD strongly suggest
caution be taken in assessing children for this disorder and providing
treatment," conclude the authors.
The ADHD medications included in the
study were methylphenidate, dextroamphetamine, mixed amphetamine salts and
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