boy with worried stressed face expression looking down with his hands pressed to either side of his face and with chaotic brain waves streaming out of his head to represent ADHD
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A study to be presented at the American College of Cardiology’s Annual Scientific Session found that young adults who were prescribed stimulant medications for attention deficit/hyperactivity disorder (ADHD) were more like to develop cardiomyopathy—a weakened heart muscle—compared with young adults who were not prescribed them.

In particular, the study showed that 17% more people who were prescribed stimulants medications for ADHD such as Adderall and Ritalin were likely to have cardiomyopathy after one year and were 57% more likely to have the condition after eight years.

“The longer you leave patients on these medications, the more likely they are to develop cardiomyopathy, but the risk of that is very low,” said lead author Pauline Gerard, a second-year medical student at the University of Colorado School of Medicine. “I don’t think this is a reason to stop prescribing these medications. There’s very little increased risk of these medications over the long term; it’s a real risk, but it’s small.”

Most prior studies assessing the safety of stimulants have focused on only the first two years after they are prescribed and have not found significant evidence of impacts to heart health. But since many patients are first prescribed these types of medications for ADHD when they are young children and continue taking them into early adulthood, the researchers designed their study to assess potential effects to the heart over a much longer period of time that is more correlative to the length of time people use them.

ADHD is one of the most common neurodevelopmental disorders in children and affects nearly one-in-ten children aged three to 17. While it is initially treated with behavioral therapy, it may eventually be combined with medications—both stimulants and non-stimulants—to more effectively manage a patient’s behavior.

For this study, the research team used the TriNeX research database that includes patient data from around 80 hospitals in the U.S. People examined in the study were between the ages of 20 to 40 years old and had been diagnosed previously with ADHD. The study group included both people who had been treated with stimulant medications for ADHD and those who hadn’t, and measured the rates of cardiomyopathy that could be tied to the use of stimulant treatments. Data from people with other heart conditions known to be caused by other factors were excluded.

For their analysis, the investigators paired patients—one who had been prescribed stimulants and one who hadn’t—who were very similar based on age, sex, and other health conditions. In total, 12,759 pairs were followed over 10 years, and the data showed that people who had taken stimulants were significantly more likely to develop cardiomyopathy throughout the 10-year period, though the gap narrowed a bit in years nine and 10.

Yet, despite this large gap, the overall incidence of cardiomyopathy was still quite low: 0.72% of patients prescribed stimulants developed cardiomyopathy compared with 0.53% of those who had not received stimulants.

To characterize what this means in the real world, Gerard noted that “You can have almost 2,000 patients on these medications for a year and you might only cause one of them to have a cardiomyopathy that they otherwise would not have had, but if you leave them on it for 10 years, one in 500 will have that happen.”

While these data don’t currently suggest changing current clinical practice to assess individual patient risk before prescribing stimulants to patients with ADHD, the research suggests the possibility of further studies that could help stratify patients into subgroups of those who may benefit from more rigorous screening.

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