Over the past two decades, rates of diagnosed attention-deficit/hyperactivity disorder (ADHD) have seen a dramatic rise in the United States. The latest data from a new study reveals that around 10 percent of children in the nation have been diagnosed with the condition.

The paper titled "Twenty-Year Trends in Diagnosed Attention-Deficit/Hyperactivity Disorder Among US Children and Adolescents, 1997-2016" was published in JAMA Pediatrics on Aug. 31.

The study used data from the National Health Interview Survey to examine individuals aged between 4 and 17. While 6.1 percent of this age group were diagnosed with ADHD during 1997-98, the researchers found that this had risen to 10.2 percent during the 2015-16 period.

But does this indicate an increase in the prevalence of the condition among children? Not quite.

It is generally believed that ADHD is common but often unrecognized. Better awareness may be the primary reason for the rise in diagnoses, said Dr. Wei Bao, study co-author and assistant professor at the University of Iowa. First, he notes that doctors and health professionals are more familiar with the condition now, improving their ability to recognize and diagnose it.

"Second, the public is more aware of this condition, increasing the possibility of affected kids being screened and diagnosed," he said. "Third, biological factors may also play a role. For example, infants born early or small survive, but they are at higher risk of developing ADHD."

However, some experts also attribute the rising numbers to the misdiagnosis of ADHD in children. "The increased rigor of kindergarten is leading to a lot of false identifications of ADHD," said Amie Bettencourt, an assistant professor at Johns Hopkins University School of Medicine. 

"This is a time when children are still developing the capacity to sit still. Years ago there was not so much sitting still. Learning was more play and experiential based," she added, encouraging caution when interpreting the new study.

Disparities were found when taking factors like race and gender into account. According to the 2015-2016 data, black children saw the highest rate of diagnoses (12.8 percent) followed by white children (12 percent) and Hispanic children (6.1 percent). In terms of gender difference, 14 percent of boys were diagnosed compared to only 6.3 percent of girls.

"Boys are usually more active than girls, therefore boys are more likely to be recognized due to hyperactivity," Dr. Bao explained. On the other hand, girls tend to manifest as attention deficit which is relatively harder to recognize than hyperactivity.

Earlier this year, scientists from the University of Southern California published a study which found a link between ADHD in teenagers and heavy digital media use. It was not clear whether the use of smartphones and other related activities directly led to the disorder, though the association was significant enough to warrant further research.