A new study reveals that the number of children overdosing on attention-deficit/hyperactivity disorder medication is increasing over time in the United States.

ADHD is reportedly the most commonly diagnosed neurobehavioral disorder in children, with a majority of the patients taking medication for it. In the United States, 6.4 million children have been diagnosed, of which an estimated 69 percent are treated with medication.

Now, research shows that ADHD diagnoses are increasing, and so is the number of exposed individuals. Exposure may be intentional or accidental, with some cases including children finding and taking the medication accidentally.

ADHD Exposure In Children, Adolescents

The study, published by the American Academy of Pediatrics, analyzed ADHD medication exposures of individuals 0 to 19 years old from 2000 to 2014. Researchers used data from the National Poison Data System, tracking calls made to poison control centers in the United States.

In this 15-year period, poison control centers received approximately 156,365 calls regarding ADHD medication exposures in people below 20 years old. Of these exposure reports, 81.9 percent were found to be unintentional. More than 40 percent were unintentional therapeutic error, while a 39.6 percent were unintentional general exposure.

Significant Trends

Most of the exposures happened to male patients (65.3 percent) and children below 12 (76 percent).

However, age became significant when it came to reasons behind the exposure. For exposures in individuals from 0 to 5, many of the incidents were unintentional general exposures, while patients 6 to 12 years old mostly showed unintentional therapeutic errors.

Alarmingly, most exposures — 50.2 percent — in the oldest age group (13 to 19 years old) were intentional.

The three deaths that occurred due to ADHD medication exposure within the study period were all teenagers, which leading author Dr. Gary Smith tells CNN was the most surprising finding in the study.

"These are stimulants, and they're used by teens for various reasons," Smith, the director of the Center for Injury Research and Policy of the Research Institute at Nationwide Children's Hospital, says in CNN. "Students, for example, might take it to get through a final exam. But like other stimulants, they might also take it because it gives them a high."

Other Trends Through The Years

Exposures to ADHD medications generally increased over the 15 years by 64 percent, but there were variations.

From 2000 to 2011, the overall reported exposures rose significantly by an overwhelming 76 percent. Then from 2011 to 2014, there was a slight dip — dubbed "nonsignificant" in the paper — of 7 percent.

The researchers are uncertain what caused the decline in 2011, saying it would be a good area of study in the future.