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It’s surprisingly common for children to have both conditions, ��ƷSM����ӰƬ researcher Erik Willcutt argues in a recently published paper

According to a coauthored by Erik Willcutt, professor of psychology and neuroscience at the ��ƷSM����ӰƬ and faculty fellow of the Institute for Behavioral Genetics, many children with attention-deficit/hyperactivity disorder (ADHD) also have reading disability, and vice versa.

“A lot of kids tend to have both learning and attentional difficulties,” says Willcutt, a clinical child psychologist by training. “Similarly, many children with reading disability also experience broader learning difficulties in areas such as math and writing.”

This research marks a shift in the clinical understanding of learning disabilities.

In recently published research, Erik Willcutt, a ��ƷSM����ӰƬ professor of psychology and neuroscience, finds that many children with attention-deficit/hyperactivity disorder also have reading disability, and vice versa.

“Twenty-five years ago, we all went into an assessment with a child thinking we had to figure out what the diagnosis is.”

“The” diagnosis—singular.

“Back then, it was always kind of surprising if a child met criteria for more than one diagnosis. We’d think, ‘Maybe we’re just wrong, and we’ve got to figure out which diagnosis is correct.’”

Yet, as research has progressed, this either-or thinking has transformed into something more like both-and thinking.

“We’ve realized over time, there are a lot of kids that really do seem to have more than one diagnosis, and that in many cases both diagnoses would benefit from treatment.”

When one diagnosis complicates another

The phenomenon of multiple diagnoses for one person is called comorbidity, a term “that came out of classic medical literature where people could have more than one illness at the same time,” says Willcutt. “For example, heart disease frequently co-occurs with other physical conditions such as diabetes, and this may mean that treatment of the heart disease is complicated by the diabetes or another co-occurring illness.”

It’s the same idea with reading disability and ADHD. “That comorbidity suggests that a child's difficulties extend beyond what they would be if that child had just reading disability.”

Reading disability, Willcutt points out, doesn’t simply mean difficulty reading. It means unexpected difficulty reading, with the expectations being based on a child’s education.

So, a child who struggles to read but hasn’t had an adequate reading education may not have reading disability. Perhaps that student struggles because he or she hasn’t grown up around books, or hasn’t been read to, or hasn’t been given adequate reading instruction. For a student such as this, difficulty reading may not be a disability so much as the natural consequence of a less-enriched reading environment.

It's the children who have had an adequate education and still underachieve in reading who may have reading disability. And if those kids also happen to have ADHD, their reading disability will likely be harder to manage, just as heart disease becomes more challenging for someone who also has diabetes.

“Individuals with more than one disorder often differ in important ways from individuals with a disorder in isolation, with the comorbid group frequently experiencing greater symptom severity, more extensive and severe functional and neurocognitive impairment, and poorer long-term outcomes,” Willcutt and co-author state in their paper.

Externalizing and internalizing behaviors

Researcher Erik Willcutt notes that reading disability doesn’t simply mean difficulty reading. It means unexpected difficulty reading, with the expectations being based on a child’s education.

There is a range of behaviors associated with reading disability and ADHD, Willcutt explains, some of which are “externalizing” and some of which are “internalizing.”

Externalizing behaviors are those that children express outwardly—“things like aggression, delinquency or conduct problems,” says Willcutt—whereas internalizing behaviors “are more internally focused—so if you feel anxious or you feel depressed or withdrawn.”

Willcutt says that reading disability and ADHD frequently co-occur with both internalizing and externalizing behaviors, but the specific profile varies among children. One student with comorbid ADHD and reading disability may continually show up late to school and disrupt class, whereas another student with the same diagnoses may be quiet and anxious.

“And there are some different behavior clusters that seem to really matter,” Willcutt adds. “The kids who have reading disability and ADHD along with early aggressive or delinquent behaviors tend to be a subgroup that is at higher risk for more severe antisocial behaviors during adolescence. On the other hand, students who have ADHD and reading disability along with internalizing symptoms often show pronounced difficulties in the classroom because they are really anxious about their academic performance.”

Assessment and treatment

Willcutt says that one key takeaway from his and Petrill’s study is that comorbidity matters and is much more common than previously thought. “At least 25% of kids who have ADHD have a learning disability, which is much higher than we would expect by random chance.”

Willcutt therefore hopes those who read his and Petrill’s study, particularly clinicians, adjust their assessment practices in a way that addresses the potential for comorbid diagnoses.

“If you’re assessing learning disabilities, it’s really important to also assess whether a child has attention problems, anxiety or conduct difficulties along with that. For clinicians who specialize in the assessment of ADHD, it's critical to include a screening measure to determine whether the child may also have learning problems. Our results suggest that it may matter quite a bit if they have a comorbid diagnosis.”

For the field more broadly, Willcutt hopes that his and Petrill’s work prompts other researchers to study treatments for comorbid learning disabilities and attentional difficulties.

“We’re at the point of saying when a child has ADHD and reading disability, both conditions really warrant interventions. Rather than trying to decide which is more important, we should really target both of them by providing the optimal intervention for reading disability and the optimal intervention for ADHD.”

In other words, if a child has both reading disability and ADHD, treating only one will likely have little to no effect on the other.

“Reading intervention might really help with the reading, but it may not address some of the other concerns that are also getting in the way for that child.”

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