Researchers examined data from U.S. poison control centers between 2000 and 2014. During this timeframe, there were more than 156,000 reported cases related to ADHD, or attention deficit/hyperactivity disorder, drug exposure (such as to popular brands like Adderall, Ritalin, and Vyvanse). And while exposures to the treatments, which can be deadly if misused or abused, dropped slightly between 2011 and 2014, the rate of incidents ballooned nearly 72% from 2000 to 2011.

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Admittedly, many of these exposures (nearly 42%) were attributable to simple medication error (although that in and of itself is also concerning from a public safety perspective). But suicide attempts and abuse of ADHD drugs accounted for more than half of the exposures for teenagers aged 13 to 19, according to the study, and one in four of all exposures involved children 12 years old and younger. More than 9,300 of these incidents required medical treatment and several children died.

So what’s driving this increase? The researchers have some theories.

“The increasing number and rate of reported ADHD medication exposures during the study period is consistent with increasing trends in ADHD diagnosis and medication prescribing. Exposures associated with suspected suicide or medication abuse and/or misuse among adolescents are of particular concern,” wrote the study authors.

Indeed, ADHD diagnoses have skyrocketed over the past few decades, according to the Centers for Disease Control (CDC). About 6.1 million children aged two to 17 had been diagnosed with the condition as of 2016, with steady rises between the beginning of the millennium and 2012. Part of that may be attributable to better screening and diagnosis of a behavioral condition that afflicts millions of American children (and adults).

But some caution may also be warranted, especially when it comes to dispensing and monitoring addictive drugs.

“The hard part is that ADHD is just like depression, just like autism, just like schizophrenia in that it’s a symptom-based mental disorder,” Berkeley psychologist and ADHD expert Dr. Stephen Hinshaw said in one interview with the American Psychological Association. “We don’t have a blood test or a brain scan yet that’s definitive. I believe that ADHD is a real condition, but it’s on a spectrum, just the way that high blood pressure and autism are. It’s always a bit arbitrary as to who is actually above the cut and who is below because we don’t know exactly where the cut is.”