Diagnosing attention-deficit hyperactivity disorder is inherently subjective. New research highlights how this can get especially tricky with young children. It shows that ADHD rates are significantly higher among children who are the youngest in their class compared with those who are the oldest. ADHD is characterised by difficulty concentrating and constantly active, sometimes disruptive behaviour. The study, published in the New England Journal of Medicine last week, found that the youngest children in early elementary school grades have a 32% higher risk of being diagnosed with ADHD than the oldest children. The study compared ADHD rates between children born in August and September in states where the cut-off birth date for school enrolment is Sept 1. Some experts say the problem may be exacerbated by a shift toward a more academic environment in early grades, which places a premium on paying attention. “We’re asking children to concentrate and focus when they don’t have the ability to concentrate and focus yet,” says R. Scott Benson, a child psychiatrist in Pensacola, Fla. “We want to be more careful, as we get more academic in these younger and younger grades, that we don’t mistake a slight developmental delay as ADHD.”
An incorrect diagnosis of ADHD could mask another problem, like not enough sleep. (ADHD medications can worsen sleep problems.) Or there may be no problem beyond the sometimes uneven behaviour of a growing child. The researchers used records from a large insurance database that included information from more than 407,000 children. The children were diagnosed with ADHD between the ages of 5 and 7. No difference was found between other month-to-month comparisons. And researchers saw no August-September difference in states with a different birth-date cut-off. The study found that 85 out of every 10,000 children born in August were diagnosed and treated for ADHD, compared with 60 per 10,000 children born in September. That means about one-quarter of children diagnosed with ADHD born in August wouldn’t have been diagnosed if they were born in September, says Anupam B. Jena, senior author on the study and an associate professor of health care policy at Harvard Medical School. He practices as an internist at Massachusetts General Hospital. Dr Jena notes that an 11-month age difference at age 5, when most children start kindergarten, represents nearly 20% of a child’s life. “If that child is born in August, that should give you some degree of pause in making a diagnosis,” he says. Researchers also examined other conditions, including asthma, anxiety and depression, and found no difference between the children born in August versus September.
Tim Layton, an assistant professor of health-care policy at Harvard Medical School and first author on the study, says the research highlights the importance of pausing before calling a doctor about a child’s unusual behaviour. “It may be the case that that behaviour is completely normal, even though it may be disruptive or make the teaching environment difficult,” he says. The rates of U.S. children diagnosed with ADHD have increased by more than 50% over the past decade. Roughly 5% to 10% of U.S. children are diagnosed with ADHD, according to the Centers for Disease Control and Prevention. More than 5% are treated with prescription drugs for the condition. Experts attribute this jump to more awareness of the condition, a real rise in the incidence of the condition, and in some cases, improper diagnosis. But there is no objective test to diagnose ADHD. Diagnosis usually involves direct observation and information from a child’s educators and parents. The NEJM study reinforces similar findings in other countries. One analysis that examined 19 studies from 13 countries evaluated rates of ADHD in the youngest children in a classroom compared with the oldest.
The conclusion: In every country studied but Denmark, the ADHD rates of the youngest exceeded those of the oldest, says Martin Whitely, first author of the study and a research fellow at Curtin University in Western Australia. The study was published in the Journal of Child Psychology and Psychiatry in October. Dr Whitely attributes the anomaly in Denmark to the fact that parents there commonly choose to delay their child’s education by a year, a practice known in the U.S. as redshirting. What most surprised Dr Whitely is what researchers found in countries like Finland with low rates of prescribing prescription drugs for children with ADHD. “Something is fundamentally wrong with the way ADHD is diagnosed,” Dr Whitely says. “There’s a whole list of things that have nothing to do with the chemistry of the brain that increases your risk of being diagnosed with ADHD.” Steven Cuffe, a child psychiatrist at the University of Florida College of Medicine in Jacksonville, says parents and especially teachers compare children to their peers when gauging behaviour for an ADHD diagnosis. He says he considers age relative to peers when he gets a referral for a child for ADHD. “A good clinician will also take the relative age of the child into account when interpreting teacher reports, and this research may help them be more sensitive to that,” he says.
Credit: Sumathi Reddy for The Wall Street Journal, 3 December 2018.