Attention deficit hyperactivity disorder (ADHD) is the most commonly diagnosed neurological disorder in children in the United States. There have been big changes in recent years in our understanding of how many kids are affected, as well as which children are most likely to get diagnosed with the disorder.
How Many Children Have ADHD in the United States?
It isn’t possible to get an exact count of the number of kids under 18 who have ADHD. Researchers use different methods to figure out who has it, so the numbers have changed over time. But there are some good estimates.
According to the CDC, more than 6 million children in the United States have the disorder. About a third of those were diagnosed when quite young -- between the ages of 2 and 5. The CDC also estimates that almost 1 in 10 children have the disorder today. That’s a much higher number than 20 years ago, when ADHD was diagnosed in just over 1 in 20 children.
Does the increase in numbers mean that more kids are getting ADHD now than they were in previous years? Maybe. But there are other explanations.
As understanding of ADHD has grown over the years, so has the ability to recognize the symptoms and diagnose the disorder. That means that children who might have slipped through the cracks before now have a better chance of getting diagnosed and treated.
Types of ADHD
The criteria that doctors use to diagnose the disorder also have changed. They were once limited to kids with hyperactive symptoms. But the definition has expanded to include kids who are primarily inattentive but don’t act out. That has increased the number of girls diagnosed with ADHD.
Primarily inattentive ADHD becomes more common with age. A review of 86 studies that looked at more than 100,000 children in total found that in preschool children, 52% of kids with ADHD have the hyperactive type of the disorder. But that number drops to 2% in elementary school and down to 14% among adolescents. Meanwhile, the number of kids with the inattentive type has risen. Among adolescents with ADHD, 72% are inattentive.
Another type of ADHD is called combined type. Kids with this form of the disorder have symptoms of both hyperactivity and inattention. It’s more common in preschoolers and elementary school children. It makes up 25% to 29% of children with the disorder.
ADHD in Boys and Girls
This condition appears to be much more common in boys than in girls. According to a 2018 study of nearly 200,000 children between the ages of 4 and 17, 14% of boys had been diagnosed with ADHD. This is compared with just over 6% of girls.
But there’s a key point to keep in mind when you look at gender differences. Boys tend to be more hyperactive than girls. Hyperactive behavior was for some time considered the principal symptom that indicates ADHD. Girls with the condition, on the other hand, are inattentive but less likely to act out. This can make the disorder harder to spot, especially in the classroom.
Another reason for the difference in numbers: ADHD research has included a smaller proportion of girls than boys. That may have skewed how well we understand the disorder. In studies that included girls, those girls often had symptoms that resembled those of boys. This reinforced the notion that girls were less likely to have the disorder. That may not be the case.
ADHD and Race
Are there racial differences in the numbers of kids with ADHD? Different studies have come up with different answers.
In one example, the CDC conducted a national survey between 2016 and 2018. It reported that 16.9% of non-Hispanic Black children between the ages of 3 and 17 had been diagnosed with ADHD. That makes Black children the most likely to have the disorder compared with non-Hispanic white and Hispanic children.
Another study, published in 2021, offers a different picture. The researchers found that 14% of white children had the disorder. This is a higher percentage than both Black and Latino children. This study also included Asian children. At 6%, this group is by far the least likely to have a diagnosis of ADHD.
In 2016, researchers reported that nearly 1 in 5 white 10th graders had received a diagnosis of ADHD at some point in their lives. That was almost twice as many as Black children and five times as many as Latino children. They reached these conclusions after accounting for factors that could have skewed the results, such as gender, household income, whether or not they had health insurance, and more.
How Do Socioeconomic Factors Affect ADHD?
Experts recognize a link between ADHD and a child’s family’s socioeconomic status. The American Psychological Association defines this as someone's social class or standing based on their education, income, and occupation. A good deal of research shows that kids from low socioeconomic-status families are more likely to have ADHD. In fact, some studies estimate that kids who grow up in such families are about twice as likely to have ADHD as kids in families that are better off financially.
Family structure and home life also play a role. Children of divorced or separated parents, for example, are more likely to live with financial hardship and experience household violence. Studies have linked both of those to ADHD in children.
But the link between ADHD and socioeconomic status is complex. Experts have different ideas about just how common it is. And they can’t explain why ADHD might be more common in families with lower socioeconomic status.