Immaturity Misdiagnosed as ADHD?

Deborah Brauser

March 08, 2012

March 8, 2012 — The youngest children in a classroom may be more likely to receive a diagnosis of attention-deficit/hyperactivity disorder (ADHD) than their older peers — a finding that raises concern "about the potential harms of overdiagnosis and overprescribing" in this vulnerable population, new research suggests.

In a cohort study of more than 900,000 Canadian children, researchers found that boys born in the month of December (the cutoff birth date for entry to school in British Columbia) were 30% more likely to be diagnosed with ADHD than boys in their grade who were born the previous January.

This number was even more dramatic in the girls, with those born in December 70% more likely to be diagnosed with ADHD than girls born in January.

In addition, both boys and girls were at a significantly higher risk of being prescribed an ADHD treatment medication if they were born in the later month than in the earlier one.

"It could be that a lack of maturity in the youngest kids in the class is being misinterpreted as symptoms of a behavioral disorder," lead author Richard L. Morrow, MA, from the Department of Anesthesiology, Pharmacology, and Therapeutics at the University of British Columbia, told Medscape Medical News.

Richard Morrow

Some of these behaviors could include not being able to sit still, not being able to focus and listen to the teacher, or not following through on a task, said Morrow.

"You wouldn't expect a 6- and 9-year-old to behave the same way, but we're often putting a 6- and 7-year-old in the same class. And we're learning that you can't expect the same behaviors from them," he added. "We would like to avoid medicalizing a normal range of childhood behaviors."

The study was published online March 5 in the Canadian Medical Association Journal.

Potential Harm

The investigators note that potential harms of overtreatment in children include increased risk for cardiovascular events, as well as effects on growth, sleep, and appetite.

"It is possible that closer consideration of a child's behavior in multiple contexts, including those outside of school, may lessen the risk of unnecessary diagnosis when assessing children for ADHD," they write.

According to the investigators, cutoff dates of birth for starting school can mean children within the same grade are almost 1 year apart in age, with significantly differing maturity levels.

Morrow noted that 2 studies published in 2010 that assessed relative age on diagnosis and treatment of ADHD in American children prompted his team to examine these issues in Canadian children.

"We weren't sure what we would find because we have a different health system here, a different cultural attitude, and different rules for advertisement of drugs," he said.

The prevalence of ADHD and the use of ADHD treatment medications are also higher in the United States than in other developed countries, including Canada, report the researchers.

For this analysis, the investigators evaluated data on 937,943 children who were between the ages of 6 and 12 years during the study period of 1997 to 2008.

Linked health databases were used to examine prescription drug use, clinical visits, hospital admissions, and demographics.

ADHD medications included in the assessments were methylphenidate, dextroamphetamines, mixed amphetamine salts, and atomoxetine.

Age-Related Effects

Results showed that 6.9% of all boys were diagnosed with ADHD vs 2.2% of the girls. In addition, 5.5% of the boys received some type of ADHD treatment vs 1.6% of the girls.

The boys who were born in December were significantly more likely to be diagnosed with ADHD than the boys born in the previous January (relative risk [RR], 1.30; 95% confidence interval [CI], 1.23 - 1.37). The percentages of the boys diagnosed with ADHD in those months were 7.4% and 5.7%, respectively.

Girls born in the last month of the year were also more likely to receive an ADHD diagnosis than the girls in their class who were born in the first month of the year (RR, 1.70; 95% CI, 1.53 - 1.88). The percentage of girls diagnosed with ADHD who were born in December was 2.7% vs 1.6% of those born in January.

A prescription for an ADHD treatment medication was significantly more likely in boys born in December than in the previous January (RR, 1.41; 95% CI, 1.33 - 1.50), as well as for girls born in December vs January (RR, 1.77; 95% CI, 1.57 - 2.00).

"An elevated risk of diagnosis and treatment for ADHD among children born in December compared with January was present for all ages from 6 to 12 years," report the investigators.

In addition to the relative immaturity of the younger students within a grade, other possible reasons cited by the researchers for age differences in ADHD diagnoses include the fact that the older kids may have been underdiagnosed or that ADHD symptoms might be amplified in younger children facing increased social pressures.

"So we might need to put more emphasis on behaviors and settings outside of school," said Morrow.

"That's already part of the standard diagnostic criteria for ADHD — that a child would be expected to show symptoms in multiple environments. But it might just need greater emphasis."

The investigators add that the "potential harms of overdiagnosis and overprescribing and the lack of an objective test for ADHD strongly suggest caution be taken."

No Need for Redshirting

"From a scientific standpoint, this a reasonable study," Mark L. Wolraich, MD, CMRI/Shaun Walters professor of pediatrics and chief of the Section of Developmental and Behavioral Pediatrics at the University of Oklahoma Health Sciences Center in Oklahoma City, told Medscape Medical News.

Dr. Mark Wolraich

"I'm not surprised by the results because behaviors found in children are going to come from a combination of their environment and their biologic makeup. So the school environment has an impact," said Dr. Wolraich. "However, I disagree with the extent that age is emphasized in a child's diagnosis."

He noted that other factors, such as the teacher's ability to structure the classroom, are also important and pointed out that over 5% of the boys born in January were also diagnosed with the disorder.

"So it's not necessarily that ADHD is caused by school environment, but certainly immaturity will make it worse," said Dr. Wolraich.

In addition, "diagnostic criteria require that you see some level of dysfunction in both the home and school. The diagnosis should not be based exclusively on school behaviors," he added.

As reported by Medscape Medical News at the time, Dr. Wolraich was chair of the subcommittee that created the American Academy of Pediatrics' updated ADHD treatment guidelines, which were published in Pediatrics in 2011.

He noted that these guidelines emphasize the need to follow criteria from the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), which include conducting interviews with both teachers and parents.

"I don't think this study will change our diagnosis recommendations. Also, it implies that you should keep kids out of school if they're at a younger age. But, as reported recently by [the American television news program] 60 Minutes, so-called 'redshirting' of kids may also have some serious implications."

The study was supported by grants from the Canadian Institutes of Health Research and the British Columbia Ministry of Health, which employs 2 of the study authors. Dr. Wolraich reported being a past consultant to Shire, Lilly, Shinogi, and Nextwave.

CMAJ. Published online March 5, 2012. Abstract


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