Several studies in recent years have found that children who are among the youngest in their class are diagnosed with ADHD at a much higher rate than their older classmates.

This suggests that a significant percentage of kids with ADHD are being misdiagnosed just because they are less mature. It raises important questions about how kids are being diagnosed, and how to avoid misinterpreting the behavior of children who might be having trouble meeting expectations just because they are younger.

The findings in these studies of large populations of kids — in Michigan, British Columbia and (most recently) Taiwan — are consistent. The youngest children are significantly more likely to be diagnosed than the oldest in the same class: boys as much as 60 percent and girls as much as 70 percent. The Taiwan study even showed the prevalence of kids diagnosed with ADHD decreased month by month from the youngest to the oldest in the class.

What can we do to address this problem while still making sure kids get the help they need?

How to avoid misdiagnosis

Most ADHD diagnoses are the result of children struggling to meet expectations for behavior and performance in school. All young children find it challenging to sit still, pay attention, wait their turn, finish tasks and keep from interrupting. By school age most have developed skills to manage these things as expected. Those who don’t are often flagged by teachers who have a lot of experience with typical behavior and child development.

But the age range of students in a given classroom can span a whole year, which means that the developmental differences between the youngest and the oldest can be substantial. That’s why it’s important that if children are being evaluated for ADHD, their behavior should be compared with that of other children their age, not all the other children in their class.

“If a child is behaving poorly, if he’s inattentive, if he can’t sit still, it may simply be because he’s 5 and the other kids are 6,” explained Todd Elder, lead author of the Michigan study. “There’s a big difference between a 5-year-old and a 6-year-old, and teachers and medical practitioners need to take that into account when evaluating whether children have ADHD.”

Here are other “best practices” that should be followed to avoid misdiagnosis:

A variety of sources:

A child shouldn’t get a diagnosis of ADHD based on a teacher’s observations alone. A clinician evaluating a child should collect information from several adults, including teachers, parents and others who spend time with him.

Not just at school:

For a child to be properly diagnosed with ADHD, the signs and symptoms that are associated with the disorder — inattention, impulsivity and hyperactivity — have to be present in more than one setting. Are they noticeable at home and in social situations, as well as school? Do his parents worry that he’s so impulsive he’s a danger to himself? Does she have trouble keeping friends because she can’t follow rules, can’t wait her turn or has tantrums when she doesn’t get her way?

Rating scales:

Scales that are filled out by teachers and parents should be used to collect specific information about the frequency of behaviors we associate with ADHD, and compare them with other children the same age, rather than relying on general impressions.

A thorough history:

To get a good, nuanced understanding of a child’s behavior, a clinician needs to know how it’s developed over time, notes Dr. Matthew Rouse, a clinical psychologist at the Child Mind Institute. “What was she like at two or three or four? Is kindergarten the first time these issues have come up, or was she kicked out of preschool because she couldn’t behave?”

Level of impairment:

The biggest difference between kids with ADHD and those who are just immature is likely to be how much their behavior impacts their lives. Are they in a negative spiral at home because they can’t seem to do what they’re asked to do, and parents are very frustrated? Are they unable to participate in sports because they can’t follow rules? Do they get excluded from play dates?

A wait and see approach

If a child is struggling because he’s immature, things could get better over time, as he adjusts to the expectations of a new classroom.

“Some children starting kindergarten might have a difficult time fitting into a new setting, adjusting to new rules,” notes Dr. Rouse. “It might be the first time the child has been in a setting with so many other kids around, and the first time taking direction from people not his parents.”

Giving kids time to adjust is one reason Dr. Rouse says that when a child presents symptoms that look like ADHD in kindergarten, when it’s his first year in school, he’ll make a provisional or “rule out” diagnosis, and reevaluate when the child is 6.

Treatment recommendations

While medication has been shown repeatedly to be the most effective at reducing symptoms of ADHD, it isn’t necessarily the go-to treatment for the youngest kids. The potential for misdiagnosis is one reason why Dr. Rouse recommends behavioral therapy for younger children with ADHD, rather than starting with stimulant medication.

Similarly, the American Association of Pediatricians recommends behavioral therapy administered by parents and teachers as the first line of treatment for children 4 to 5 years old. Stimulant medication is recommended only if the behavioral therapy doesn’t produce results, and the child continues to have moderate to severe symptoms.

Delay in brain development

One reason immaturity might be confused with ADHD is that ADHD itself has been linked to a delay in brain maturation. An older child with ADHD might present behaviors that are typical in a younger child — and the opposite could be true if your frame of reference is older children. Several important neuroimaging studies have shown delays in brain development in kids with ADHD.

In a 2006 study at the National Institutes of Mental Health, the brains of several hundred children were scanned over a 10-year period. As the brain matures, the cortex thickens and then thins again following puberty, when connections are pruned to increase the efficiency of the brain. Researchers found that what they call “cortical maturation” — the point in which the cortex reaches peak thickness — was three years later in kids with ADHD than kids in a control group: 10.5 years old, compared to 7.5. The kids with ADHD also lag behind other kids in the subsequent cortical thinning.

The researchers noted that the most delayed areas of the brain are those that “support the ability to suppress inappropriate actions and thoughts, focus attention, remember things from moment to moment, work for reward and control movement – functions often disturbed in people with ADHD.”

They also added, tantalizingly, that the only area that matured faster than usual in kids with ADHD was the motor cortex. Combine that with the late-maturing frontal cortex areas that direct it, and the mismatch, they suggested, could account for the restlessness associated with the disorder.

Then in 2013, a study using scans of brain functioning, rather than structure, also found a lag in maturity in kids with ADHD. That study, at the University of Michigan, found that children and teens with ADHD are behind others of the same age in how quickly their brains form connections within, and between, key brain networks.

Specifically, they found less-mature connections between what’s called the “default mode network,” which controls internally directed thought, and networks that focus on externally directed tasks. Researchers propose that this lag in connectivity could help explain why children with ADHD find their thoughts wandering and struggle to complete tasks and stay focused.

Maturing out of ADHD symptoms

Finally, we know that some children grow out of ADHD symptoms as they become teenagers and young adults. Hyperactive and impulsive symptoms often wane through adolescence, while inattentive symptoms may continue to be a problem into adulthood.

Regardless of whether or not a child has ADHD, if his behaviors interfere with learning, making friends and being a part of the family, then he needs help. But the behavioral therapies and medications that can work wonders for kids with ADHD aren’t appropriate for children who are struggling to meet expectations just because they are less mature than those they are being compared to.

There are also other problems that can be misread as ADHD. Anxiety and trauma, for instance, can also cause inattention and what looks like impulsivity. That’s why it’s important that kids with behavior issues be evaluated thoroughly; careful and effective diagnosis benefits everyone.

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